Childhood asthma and exposure to indoor allergens: low mite levels are associated with sensitivity

Exposures in the Indoor Environment and Prevalence of Allergic Conditions in the United States of America

Our study examines the association of the presence of mildew, cockroaches, and pets in homes as well as household dust allergens with the prevalence and/or severity of allergic diseases. No study has concurrently assessed home environment exposures in relation to allergic conditions in the general US population. Data from 5409 participants from the 2005–2006 National Health and Nutrition Examination Survey (NHANES) living in their current homes for ≥one year were analyzed. Multivariate logistic regression analyses between home exposures and allergic diseases prevalence and severity were performed. In adjusted analyses, mildew was associated with higher current asthma, allergies, and allergic rhinitis prevalence; endotoxin, with higher current asthma prevalence; and dust Canis familiaris (Can f) 1, with higher allergic rhinitis prevalence. However, presence of cockroaches and dust Dermatophagoides farinae (Der f) 1 were associated, respectively, with lower current asthma and allergies prevalence. Presence of mildew, dust Der f1, Dermatophagoides pteronyssinus (Der p) 1, Felis domesticus (Fel d) 1, and endotoxin were all associated with asthma and/or wheeze severity. Non-atopic asthma was more frequent with mildew and/or musty smell dust and higher dust Fel d1 concentration, while atopic asthma was more prevalent with higher Can f1 and endotoxin concentrations in dust. This study confirms previous relationships and reports novel associations, generating hypotheses for future research.

Home Environmental Interventions for House Dust Mite

It has been 50 years since the dust mite was first appreciated to be a major source of allergen in house dust, and by extension a key trigger of allergic respiratory disease. Since that time a number of protein allergens have been identified and characterized, mainly from mite feces, and standardized mite extracts and IgE assays have been developed. Insights into the lifecycle of dust mites and aspects of mite allergen biology have shed light on the mechanisms that lead to respiratory disease and to the development of interventions that can minimize dust mite allergen exposure. It is now clear that dust mite allergy is a key contributor to asthma in many parts of the world, and that long-term avoidance can be effective for preventing sensitization and minimizing the development and severity of respiratory disease. Here, we discuss the evidence linking dust mites with respiratory disease, outline studies that support the efficacy of home environmental interventions, and highlight practical methods that have been shown to be effective as part of a multifaceted approach to dust mite avoidance.

Repeated immunosensing by a dithiobis(succinimidyl propionate)-modified SAW device

The possibility of dithiobis(succinimidyl propionate) (DSP) for repeated immunoassay with a surface acoustic wave (SAW) immunosensor was explored. In the sensor, DSP was used to modify a gold-coated quartz sensing area of a SAW device by forming a self-assembled monolayer on the gold surface. In a model sandwich assay using mouse (mIgG) and anti-mouse (a-mIgG) antibodies, the primary antibody, mIgG, firstly reacted with N-hydroxysuccinimide ester groups of DSP and was immobilized on the SAW device to fabricate the SAW immunosensor. Optimization of adsorption time of mIgG revealed that both degrees of adsorption and immobilization of mIgG reached a saturation at 30 min although the immobilization was more dependent on the adsorption time. Through characterization of the DSP-modified SAW immunosensor, a high selectivity, with which no sensor output was observed from various kinds of secondary antibodies except for a-mIgG, along with 8-fold shorter measurement time (15 min) than that of enzyme-linked immunosorbent assay were obtained. Furthermore, 10 repeated measurement of a-mIgG demonstrated a high reproducibility of the sensor output (coefficient of variation of 7.0%). These validate the utility of DSP in the SAW immunosensor for rapid and repeated measurement of antigens.

Ecological determinants of respiratory health: Examining associations between asthma emergency department visits, diesel particulate matter, and public parks and open space in Los Angeles, California

Los Angeles County (LAC) low-income communities of color experience uneven asthma rates, evidenced by asthma emergency department visits (AEDV). This has partly been attributed to inequitable exposure to diesel particulate matter (DPM). Promisingly, public parks and open space (PPOS) contribute to DPM mitigation. However, low-income communities of color with limited access to PPOS may be deprived of associated public health benefits. Therefore, this novel study investigates the AEDV, DPM, PPOS nexus to address this public health dilemma and inform public policy in at-risk communities. Optimized Hotspot Analysis was used to examine geographic clustering of AEDVs, DPM, and PPOS at the census tract unit of analysis in LAC. Ordinary Least Squares (OLS) regression analysis was used to examine the extent to which DPM and PPOS predict AEDVs. Finally, Geographic Weighted Regression (GWR) was employed to account for spatial dependence in the global OLS model. Optimized Hotspot Analysis confirmed significant clustering of elevated AEDVs and DPM in census tracts with reduced PPOS. After controlling for pertinent demographic characteristics (poverty, children, race/ethnicity), regression analysis confirmed that DPM was significantly positively associated with AEDVs, whereas PPOS was significantly negatively associated with AEDVs. Furthermore, GWR revealed that 71.5% of LACs census tracts would benefit from DPM reductions and 79.4% would benefit from PPOS increases toward redressing AEDVs. This is the first study to identify AEDV reductions in census tracts with higher concentrations of PPOS. Thus, reducing DPM and increasing PPOS may serve to improve asthma outcomes, particularly in low-income communities of color.

Allergic rhinoconjunctivitis continued to increase in Swedish children up to 2007, but asthma and eczema levelled off from 1991

AIM

This study investigated whether allergies among schoolchildren increased in Sweden between 1979 and 2007 and whether the geographical differences observed in previous studies remained.

METHODS

We collected questionnaire data on asthma, allergic rhinoconjunctivitis (ARC) and eczema in children aged seven to eight years from Mölndal, Gothenburg, in south-western Sweden and Kiruna in northern Sweden in 1979 (n = 4682), 1991 (n = 2481) and 2007 (n = 1029). The same regions and questions were used in all three studies, and extra questions on food allergy or intolerance were added in 2007.

RESULTS

In 1979, 1991 and 2007, the total prevalence of asthma was 2.5%, 5.7% and 7.1%, ARC was 5.5%, 8.1% and 11.1% and eczema was 7.1%, 18.3% and 19.7%, respectively. Asthma prevalence remained higher in Kiruna, but no significant regional differences were seen for ARC and eczema. Almost 20% reported a history of food allergy or intolerance, with a higher prevalence in Kiruna. The allergy risk was reduced if both parents were born outside Sweden.

CONCLUSION

The prevalence of ARC continued to increase between 1991 and 2007, but increases in asthma and eczema started to level off in 1991. Some geographical differences remained, but total allergy rates were similar in Kiruna and Mölndal in 2007.

"A year-long, fortnightly, observational survey in three European countries of patients with respiratory allergies induced by house dust mites: Methodology, demographics and clinical characteristics"

BACKGROUND

House dust mite (HDM) allergens constitute the leading trigger for the symptoms of persistent respiratory allergies (such as allergic rhinitis and asthma). However, the fluctuating, pernicious nature of the symptoms has given rise to a perception that HDM-induced respiratory allergy is not a "real" disease.

METHODS

In order to assess the self-reported disease profile and behaviour of adult patients with a self-reported history of severe, poorly controlled, physician-diagnosed HDM respiratory allergy, we performed an observational, international, multicentre survey in three European countries (France, Italy and Spain). Participants were included in the survey if they passed a short Internet-based screening questionnaire. Following completion of a detailed post-inclusion questionnaire, 28 fortnightly telephone interviews were used to gather extensive data on the participants' symptom prevalence and intensity, medical consultations, disease burden, quality of life, and medication use from late May 2012 to early July 2013.

RESULTS

Twenty-two thousand nine hundred ninety five individuals completed the Internet screening questionnaire and 339 respondents (67 % female) met all the inclusion criteria. 313 of the 339 (92 %) completed the post-inclusion questionnaire (n = 114 in Italy, 92 in France and 107 in Spain). The median time since the first symptoms of HDM allergy was over 13 years in all three countries. The response rate for the fortnightly interviews averaged 75 % (range: 29 to 97 %). The reported fortnightly prevalence of nasal and ocular symptoms peaked in the autumn (September to November) and spring (March to May). These peaks in prevalence coincided with increased reports of symptom worsening and higher physician consultation rates. In participants not allergic to pollen, the autumn and spring peaks were accompanied by a third peak in late December 2012. Very few participants reported that their symptoms had never improved (4 %) or never worsened (11 %) during the survey period.

CONCLUSIONS

In a survey in France, Italy and Spain, patients with severe HDM-induced respiratory allergies experienced a complex set of changing, troublesome symptoms throughout the year, with peaks in spring, autumn and (to a lesser extent) mid-winter.

Housing and child health

The connection between housing and health is well established. Physical, chemical, and biological aspects of the child's home, such as cleanliness, moisture, pests, noise, accessibility, injury risks, and other forms of housing environmental quality, all have the potential to influence multiple aspects of the health and development of children. Basic sanitation, reduced household crowding, other improvements in housing and expanded, and improved housing regulations have led to advances in children's health. For example, lead poisoning prevention policies have profoundly reduced childhood lead exposure in the United States. This and many other successes highlight the health benefits for families, particularly children, by targeting interventions that reduce or eliminate harmful exposures in the home. Additionally, parental mental health problems, food insecurity, domestic violence, and the presence of guns in children's homes all are largely experienced by children in their homes, which are not as yet considered part of the Healthy Homes agenda. There is a large movement and now a regulatory structure being put in place for healthy housing, which is becoming closely wedded with environmental health, public health, and the practice of pediatrics. The importance of homes in children's lives, history of healthy homes, asthma, and exposures to lead, carbon monoxide, secondhand/thirdhand smoke, radon, allergy triggers is discussed, as well as how changes in ambient temperature, increased humidity, poor ventilation, water quality, infectious diseases, housing structure, guns, electronic media, family structure, and domestic violence all affect children's health.

The relationship between a specific IgE level and asthma outcomes: results from the 2005-2006 National Health and Nutrition Examination Survey

BACKGROUND

Allergen exposure is associated with increased specific IgE (sIgE), and allergen exposure plus sensitization is predictive of asthma outcomes. However, it is not known if sIgE is predictive of asthma outcomes in the absence of exposure data.

OBJECTIVE

To investigate whether IgE to indoor allergens is predictive of and has a dose-response relationship with asthma emergency department (ED) visits and wheeze.

METHODS

In the 2005-2006 National Health and Nutrition Examination Survey, 351 children and 390 adults reported current asthma. Continuous sIgE to 9 indoor allergens were considered. Asthma morbidity in the past year was measured by wheezing. Health care utilization was defined as any asthma ED visits in the past year.

RESULTS

Analyses were adjusted for race, age, education, poverty index ratio and (in adults) tobacco use. In children, ED visits were associated with cockroach (odds ratio [OR] 1.5 [95% CI, 1.1-2 .1), rat (OR 1.9 [95% CI, 1.2-2.8]), and Aspergillus (OR 1.6 [95% CI, 1.001-2.60]). Continuous Aspergillus (OR 1.5 [95% CI, 1.04-2.1), Alternaria (OR 1.4 [95% CI, 1.1-1.6]), and total IgE (OR 1.2 [95% CI, 1.1-1.4]) were associated with wheeze in children. Adult ED visits were associated with sIgE for dust mites (Dermatophagoides pteronyssinus OR 1.6 [95% CI, 1.3-2.1]; Dermatophagoides farinae OR 1.6 [95% CI, 1.3-1.9]), total IgE (OR 1.4 [95% CI, 1.04- 1.9]), and the sum of sIgEs (OR 1.6 [95% CI, 1.2-2.2]).

CONCLUSIONS

Sensitization to particular indoor environmental allergens was found to be a risk factor for wheeze and asthma ED visits. These outcomes increased as the concentration of sIgE to these allergens increased.

The association between fractional exhaled nitric oxide (FeNO) and cat dander in asthmatic children

BACKGROUND

The aim of our study was to assess risk factors of increased FeNO in asthmatic children with no cat at home.

METHODS

It was a retrospective, cross-sectional study. We evaluated data from medical documentation of children with asthma: FeNO results, allergen sensitization, seasonal allergen exposure, FEV(1), allergic rhinitis (AR) diagnosis and cat presence at home. We assessed asthma severity using mean doses of inhaled glucocorticosteroids and a management approach based on control according to the newest guidelines of Global Initiative for Asthma (GINA) throughout the last three months before the measurement of FeNO and spirometry.

RESULTS

316 patients (age 6-18) completed the study. Sensitization to cat dander was associated with the highest median value of FeNO concentration compared to other allergens in our patients (28,4ppb) and co-existing sensitization did not affect FeNO level. Median levels of FeNO increased linearly with patient's age. In asthmatics with AR, the levels of FeNO were increased significantly compared to asthmatics without AR (20.8 vs. 16.3, respectively). We showed that in patients without AR, sensitization to cat allergen was associated with more severe asthma in comparison to other perennial allergy (step 4 vs. other steps according to GINA treatment steps). The above relation was not observed in patients with AR. We did not observe correlation between allergy profile and FEV(1) among patients in neither subgroup nor in general population.

CONCLUSIONS

We revealed that sensitization to cat dander was associated with the highest increase of FeNO concentration compared to other allergens in patients not having any cat at home ever. We also observed that in patients without allergic rhinitis, sensitization to cat allergen, compared to other perennial allergy, was associated with more severe asthma.

Anti-cockroach and anti-mouse IgE are associated with early wheeze and atopy in an inner-city birth cohort

BACKGROUND

The relationships between cockroach and mouse allergen exposure, anti-cockroach and anti-mouse IgE, and wheeze, rhinitis, and atopic dermatitis in children as young as age 3 years are of public health importance but have not been thoroughly evaluated.

OBJECTIVE

We hypothesized that inner-city children might have anti-cockroach and anti-mouse IgE by age 3 years, and their presence would be associated with respiratory and atopic symptoms.

METHODS

Children were followed prospectively from birth through age 3 years (n = 404). Residential levels of cockroach and mouse allergens, sera levels of anti-cockroach and anti-mouse IgE, and parental report of wheeze, rhinitis, and atopic dermatitis were measured.

RESULTS

The odds of early wheeze were significantly higher among children who had IgE to cockroach (odds ratio [OR], 3.3; 95% CI, 1.8-6.2), mouse (OR, 4.6; 95% CI, 2.3-9.0), or both (OR, 9.7; 95% CI, 3.4-27.3). The odds of rhinitis or atopic dermatitis were also higher among children with IgE to cockroach, mouse, or both. Higher IgE class to cockroach and mouse was associated with wheeze and atopic dermatitis (tests for trend, P < .002).

CONCLUSIONS

Children age 2 to 3 years who have anti-cockroach and anti-mouse IgE are at increased risk of wheeze and atopy. Moreover, a dose-response relationship was found between higher IgE class and increased prevalence of wheeze, rhinitis, or atopic dermatitis. These findings indicate the importance of reducing exposure to cockroach and mouse allergens for susceptible children.

Risk of wheezing associated with house-dust mite allergens and indoor air quality among three-year-old children. Kraków inner city study

OBJECTIVES

The aim of the study was to describe the distribution of house-dust mite (HDM) allergens in homes of three-year-old children and to test the hypothesis whether the content of HDM allergens exceeding 2 microg/g of dust may be regarded as a risk level possibly affecting respiratory health in early childhood.

MATERIALS AND METHODS

House-dust samples were collected in 275 dwellings from mattresses, children's bedrooms and kitchen floors. In the laboratory, dust samples were analyzed for Der f 1 and Der p 1 using monoclonal antibody enzyme-linked immunosorbent assays (ELISA). At the time of the house-dust collection, mothers were interviewed on the household characteristics and their children's respiratory health. Respiratory outcome variables included wheezing or whistling in the chest irrespective of respiratory infections. The number of the wheezing episodes and their duration in days over the last 6 months were recorded in the questionnaire. In the multivariate Poisson regression analysis on the association between the occurrence of wheezing and exposure, a set of potential confounders, such as child's gender, maternal education, maternal allergy, older siblings, presence of moulds, house dampness, and environmental tobacco smoke (ETS) was taken into account.

RESULTS

The adjusted incidence rate ratios (IRR) of wheezing ascribed to a higher HDM level (> 2.0 microg/g dust) were 1.84 (95% CI: 1.45-2.34) for duration of wheezing and 1.56 (95% CI: 0.88-2.75) for episodes. Of the confounders taken into consideration, the presence of moulds had the strongest impact on the risk of wheezing (IRR = 4.24; 95% CI: 3.08-5.84).

CONCLUSION

The data support the view that exposure to a higher level of HDM allergens increases the burden of respiratory diseases in the early childhood and the effect is independent of maternal atopy, ETS, and moulds in homes.

Skin sensitization in school children in northern and southern Norway

It has been suggested that environmental exposures and living conditions can explain some of the worldwide variation in atopic disorders. Norway has large environmental contrasts within the country. We compared skin prick sensitization rates among school children living in the southern subarctic and in the northern arctic part of Norway. Approximately one quarter of the children were sensitized, mostly against pollen and animal dander, while mite and mould sensitization seemed to be a minor problem. Sensitization rates and profiles were similar in the north and south despite differences in living conditions and environmental exposures.

Correlation between inhalant allergen-specific IgE and pulmonary function in children with asthma

Sensitization to aeroallergens is associated with diminished lung function in adults. Little has been studied on the relationship between the inhalant allergen-specific IgE and pulmonary function in asthmatic children. This study was focused on four major inhalant allergens found in Korea, including Dermatophagoides pteronyssinus (Der p.), Dermatophagoides farinae (Der f.), and Alternaria- and German cockroach-specific IgEs, with evaluation of pulmonary function in relation to the amount of allergens. The parents or legal guardians of participants enrolled in this study gave informed consent. Fifty-five asthmatic patients and 48 nonasthmatic children were included. The amounts of specific IgE for the four specified inhalant allergens were determined by employing the CAP system FEIA. Forced expiratory volume in 1 sec (FEV(1))/forced vital capacity (FVC), FEV(1), and forced expiratory flow between 25% and 75% of FVC (FEF(25-75)) of subjects were evaluated through pulmonary function tests. In the asthmatic group, FEV(1), FEV(1)/FVC, and FEF(25-75) were significantly reduced (P < 0.05): reduction in FEV(1) (r = -0.44) and FEF(25-75) (r = -0.33) in association with the Der f.-specific allergen, and reduction in FEV(1) (r = -0.37) and FEF(25-75) (r = -0.34) in association with the Der p.-specific allergen, were observed. However, there was no significant correlation with German cockroach and Alternaria allergen. In the control group, no significant correlation was detectable between the allergen-specific IgE titers and the results of pulmonary function tests. In asthmatic patients, Der p.- and Der f.-specific IgEs, and not German cockroach and Alternaria, seem to play a considerable role in reduced pulmonary function among asthmatic children.

Effects of early intake of fruit or vegetables in relation to later asthma and allergic sensitization in school-age children

AIM

To assess the associations between nutrition supplements in infancy and later asthma and allergy in school-age children, and to explore the impact of environmental factors in early life.

METHODS

Five hundred and two children underwent clinical examination, skin prick test and a second parentally completed questionnaire within 2 y of a cross-sectional questionnairebased study, including 4585 primary school children (6-16 y old) in 1994 from urban Oslo (37%), the mountainous area of Hallingdal (42%), and the industrial, coastal area of Odda (21%). The children were selected from the 1994 survey on the basis of reported diagnosed asthma (n=166), wheeze in the last 12 mo (n=155) and no asthma/no wheeze (n=181). Questions were related to nutrition and environmental exposure in early life. Possible associations between allergic sensitization or asthma at school age and exposures were estimated by logistic regression analysis, adjusting for potential confounders.

RESULTS

Daily intake of fresh fruit or vegetables, but not extra vitamins or cod liver oil supplements, in infancy decreased the risk of asthma (adjusted odds ratio (aOR) 0.57 (95% confidence interval (CI): 0.37-0.88). Early supplements of cod liver oil and extra vitamins were associated with increased allergic sensitization (aOR 1.78 (95% CI: 1.03-3.07) and 1.71 (95% CI: 1.01-2.88), respectively). A significantly higher prevalence of allergic sensitization was found in children living in Hallingdal compared to Odda, while the latter children, on the other hand, had the highest prevalence of house dust mite allergy (p = 0.001 vs Hallingdal and p = 0.04 vs Oslo).

CONCLUSION

The present study suggests that the early introduction of daily fresh fruit or vegetables may decrease the risk of asthma after 1 y of life, whereas allergic sensitization at school age seemed to increase with extra vitamin and cod liver oil supplements during infancy. Living area influenced allergic sensitization, with differences between coastal and inland areas.

Prenatal exposure to house dust mite allergen (Der p 1), cord blood T cell phenotype and cytokine production and atopic dermatitis during the first year of life

This study investigated the influence of prenatal exposure to house dust mite (HDM, D. pteronyssinus) on interleukin (IL)-2, interferon-gamma (IFN-gamma) and IL-4 producing CD4(+) and CD8(+) T lymphocytes in cord blood as well as on the development of sensitization and occurrence of atopic dermatitis (AD) as the first symptom of allergy during the first year of life. Dust samples (n = 22) were collected by vacuum cleaning the maternal mattress during early to mid-pregnancy. In these samples, the amount of the major HDM antigen (Der p 1) was assessed by a sensitive enzyme-linked immunosorbent assay technique (detection limit 0.004 microg/g dust). Flow cytometry was used to determine cord blood lymphocyte subtypes and to quantify the intracellular amounts of IL-2, IFN-gamma and IL-4 produced by cord blood CD4(+) helper and CD8(+) cytotoxic T lymphocytes, both spontaneously and after stimulation with phorbol-12-mirystate-13-acetate and ionomycin. Children were followed for 1 yr for the presence of symptoms associated with allergy. In addition, at the age of 1 yr specific IgE to different classical inhalant and food allergens was measured. Higher prenatal exposure to Der p 1 (>0.2 microg/g dust) was associated with a significant lower percentage of IFN-gamma producing stimulated CD4(+) T lymphocytes, compared with lower prenatal Der p 1 exposure (p = 0.03). The presence of AD during the first year of life (n = 9) was associated with an increased number of naive CD4(+) CD45RA(+) lymphocytes (p = 0.03), with an increased spontaneous IL-4 production by CD8(+) lymphocytes (p = 0.04) and with a decreased percentage of IFN-gamma producing stimulated CD4(+) lymphocytes (p = 0.04). Furthermore, exposure to HDM during pregnancy tended to be higher in mothers of children with AD during the first year of life when compared with those without AD (p = 0.08). This study shows that the level of prenatal exposure to Der p 1 influences the immune profile of cord blood T lymphocytes and the clinical outcome in early life. Therefore, the prenatal environment must be regarded as a possible early risk factors for allergic diseases in children.

Variability of airborne cat allergen, Fel d1, in a public place

Allergen exposure is a risk to develop an IgE-mediated sensitization. The amount of allergen inhaled per unit time should be related to the amount present in the air, i.e. airborne allergen. Thus, measuring allergen levels in the air would be more relevant than measuring allergen levels in dust. Allergens are present in the air in very minute quantities and usually become airborne after disturbance. Large variation of allergen levels have been found in dust. In this study, we measured variability of airborne cat allergen, Fel d1, in a public place using a high-volume air-sampler. We also studied the distribution and relationship between dust and airborne cat allergens in homes and schools. Air samples were collected at three different airflow rates, i.e. 55, 40, and 30 m3 of air per hour. The concentration of airborne Fel d1 in the community gymnastic hall varied from 1 to 10 pg/m3 within a period of 3 weeks, at airflow rates 55-30 m3/h. The coefficient of variation for repeated samplings was 14-43% (day-to-day variation) and 27-38% (within-day variation). As expected, higher levels of airborne cat allergens were found in homes with cats than in cat-free environments. There was a significant relationship between cat allergen levels in dust and air (r=0.7, P<0.01). Our study demonstrates that when measuring airborne cat allergen a large variation is observed within a day and between days. The large variability of measurement may be explained by the disturbance in the environments. We suggest, that when exposure assessment is made the environment in question should be analyzed, if possible in several occasions.

Disodium octaborate tetrahydrate (DOT) application and vacuum cleaning, a combined strategy to control house dust mites

BACKGROUND

The effectiveness of acaricides in homes is controversial.

OBJECTIVE

To determine whether disodium octaborate tetrahydrate (DOT) combined with vacuuming lowers dust mite numbers and their allergens in carpets and sofas.

METHODS

A 6-month study was carried out with 93 homes, which were randomized into three groups: (i). active, received DOT; (ii). placebo, received water; and (iii). control, received no application. Active and placebo homes were vacuumed weekly. Dust was collected from carpets and sofas at the start of the study and every 2 months thereafter and quantified for live, total mites, and mite allergen levels.

RESULTS

At 2 months, live mite numbers in active carpets were 3 +/- 1, in placebo carpets 129 +/- 48, and in control carpets 177 +/- 39 mites/g. The corresponding numbers in sofas were 3 +/- 2, 81 +/- 31, and 134 +/- 45 mites/g, respectively (P < 0.001 active vs placebo and vs. control). Live mites in carpets and sofas remained lower in the active group at 6 months (P < 0.001). Total mites in active carpets decreased from 555 +/- 69 at baseline to 223 +/- 32 mites/g at 6 months (P < 0.001) and mite allergen levels from 1.36 +/- 0.13 to 0.85 +/- 0.16 microg/g (P < 0.001). Total mites in active sofas remained unchanged, but mite allergen levels decreased from 1.48 +/- 0.25 at baseline to 0.7 +/- 0.15 microg/g at month 6 (P < 0.05).

CONCLUSION

DOT kills mites in carpets and sofas, and, combined with vacuuming, effectively reduces total mites in carpets and mite allergen levels in carpets and sofas.

Allergen sensitivity and asthma severity at an inner city asthma center

The objective of this study was to examine the relationship of allergen sensitivity to asthma symptoms among inner-city asthmatics seen at our Brooklyn, NY, asthma center. We hypothesized that asthma severity would increase for adults and children with increased cockroach and dust mite allergen sensitivity. Data were gathered from retrospective chart review for all patients who were treated at the center with a diagnosis of asthma and had undergone skin-prick testing (SPT) for allergen sensitivity during 1998 (pediatric, n = 79; adult, n = 29). Asthma severity (determined by National Heart, Lung and Blood Institute [NHLBI] asthma severity class) was examined in relation to allergen sensitivity. Allergen sensitivity was measured by percent positive to skin-prick testing as well as by relative mean diameter of skin prick test wheals. For adults, mite sensitivity prevalence was 61% and cockroach sensitivity prevalence was 41%. For children, mite sensitivity prevalence was 49%; cockroach sensitivity prevalence was 42%. For adults, asthma severity correlated significantly with sensitivity to Cladosporium, tree, and grass as measured by percent positive skin tests and by increasing mean diameter of skin test wheals. There was a significant correlation with severity for adult dust mite sensitivity only as measured by increasing mean wheal diameter. Ragweed sensitivity showed a significant correlation with severity only as measured by percent positive skin tests. There was a significant positive association for adults between increasing asthma severity and total number of allergen sensitivities per subject. There was no significant correlation for children between asthma severity and total number of allergen sensitivities per subject. Among children, no specific allergen sensitization showed a significant positive association with asthma severity. By both measures of allergen sensitization, there was a significant negative association for children between Cladosporium and asthma severity. Among our inner-city asthmatic population significant correlation between mite sensitivity and asthma severity was found only in adults. No significant association was seen with cockroach. However, outdoor allergen sensitivity (Cladosporidium, tree, ragweed, and grass) significantly correlated with asthma for adults in this inner city population.

Pets in the home and the development of pet allergy in adulthood. The Copenhagen Allergy Study

BACKGROUND

The aim of the study was to investigate the association between exposure to cat and dog in the home and the development (incidence) of IgE sensitization to cat and dog.

METHODS

Participants in a population-based study of 15-69-year-olds in 1990 were invited to a follow-up in 1998. Serum IgE antibodies against common inhalant allergens was assessed in 734 subjects (participation rate 69.0%) on two occasions 8 years apart. Information about current or previous keeping of cats and dogs in the home was obtained in a questionnaire at baseline.

RESULTS

A cat in the home currently was significantly associated with the development of IgE sentisization to cat (adjusted odds ratio 8.4, 95% confidence interval (CI) 1.7-42.7). Moreover, an atopic predisposition in terms of IgE sensitization to allergens other than cat at baseline was an independent risk factor for the development of IgE sensitization to cat. A dog in the home was not significantly associated with the development of IgE sensitization to dog.

CONCLUSIONS

In this adult population, exposure to a cat in the home increased the risk of developing IgE sensitization to cat. More prospective data are needed on this issue.

The impact of climate and traffic-related NO2 on the prevalence of asthma and allergic rhinitis in Italy

BACKGROUND

Environmental factors are likely to be involved in explaining the wide geographical variation in asthma and atopic diseases that has been documented in many recent epidemiological studies.

AIM

To evaluate to what extent climate and outdoor NO2 pollution can explain the geographical variation in the prevalence of asthma and allergic rhinitis, and to estimate the relative risk for exposure to different levels of these two factors.

METHODS

The impact of climate and long-term exposure to nitrogen dioxide (NO2) pollution on asthma and allergic rhinitis was assessed in a cross-sectional study, carried out during 1998 to 2000 on young adults aged 20 to 44 years (n = 18 873), living in 13 areas from two different Italian climatic regions (subcontinental and Mediterranean).

RESULTS

Mediterranean areas had a significantly higher prevalence of asthma-like symptoms (P < 0.001), higher annual mean temperature (16.2 degrees C vs. 12.9 degrees C), lower temperature range (16.0 C degrees vs. 22.1 degrees C) and lower NO2 levels (31.46 microg/m3 vs. 57.99 microg/m3) than subcontinental ones. Mediterranean climate was associated with an increased risk of wheeze (OR = 1.23; 95% CI 1.13 to 1.35), tightness in the chest (OR = 1.21; 95% CI 1.11 to 1.33), shortness of breath (OR = 1.21; 95% CI 1.08 to 1.36) and asthma attacks (OR = 1.19; 95% CI 1.07 to 1.31). After adjusting for climate, an increase of 18.3 microg/m3 in NO2 levels moderately increased the risk of asthma attacks (OR = 1.13; 95% CI 0.98 to 1.32), tightness in the chest (OR = 1.11; 95% CI 0.98 to 1.26) and wheeze (OR = 1.11; 95% CI 0.96 to 1.28). When the levels of outdoor NO2 exposure rose, the prevalence of allergic rhinitis increased significantly in the Mediterranean region (OR = 1.38; 95% CI 1.12 to 1.69), but not in the subcontinental one (OR = 1.03; 95% CI 0.83 to 1.28).

CONCLUSION

Our results show that the prevalence of asthma increases when annual mean temperature increases and temperature range decreases. Furthermore, climate interacts with NO2 outdoor exposure, increasing the risk for allergic rhinitis in people exposed to high stable temperatures. A long-term role for the effect of traffic pollution on asthma is also suggested.

Levels of house dust mite-specific IgE and cockroach-specific IgE and their association with lower pulmonary function in Taiwanese children

OBJECTIVE

Sensitization to an aeroallergen is known to diminish pulmonary function in young children and adults; however, it remains unclear whether it produces similar effects in adolescents. This study, therefore, examined the relationship between serum allergen-specific IgE levels and pulmonary function in adolescents.

DESIGN

Middle-school children were invited for a physician's evaluation and pulmonary function test when not experiencing an asthma attack and for the determination of serum levels of specific IgE to common allergens.

SETTING

National Cheng Kung University Hospital, Taiwan.

SUBJECTS

Middle-school children in southern Taiwan, who had completed both a nationally administered Chinese version of the International Study of Asthma and Allergies in Childhood questionnaire and a pulmonary function test in October 1996.

RESULTS

Forty-two then currently asthmatic children, 38 children with asthma in remission (no reported attack for > 12 months), and 69 children without asthma completed the study. Children with asthma had a significantly lower adjusted forced expiratory flow between 25% and 75% of FVC (FEF(25-75%)) and FEV(1)/FVC than children without asthma. A greater percentage of children with asthma were more sensitized to Dermatophagoides pteronyssinus (Der p), Dermatophagoides farinae (Der f), and German cockroach but not cat dander or dog dander. Children with asthma with Der f-specific IgE > 100 IU/mL, or cockroach-specific IgE > 0.7 IU/mL showed lower pulmonary function. No such association was found in children without asthma.

CONCLUSION

Our findings suggest that sensitization to Der f and German cockroach was a critical factor for the lower pulmonary function observed in middle-school children with asthma.

An ELISA for recombinant Lepidoglyphus destructor, Lep d 2, and the monitoring of exposure to dust mite allergens in farming households

BACKGROUND

Exposure to indoor allergens, such as dust mites, has been recognized as a risk factor for sensitization and symptoms.

OBJECTIVE

To develop a two-site ELISA for the determination of Lep d 2 in the reservoir, to measure dust mite allergen exposure (Lep d 2, Der p 1, Der f 1 and Der 2) in farm households, and to investigate whether exposure to these allergens is associated with sensitization, asthma and rhinoconjunctivitis.

METHODS

Monoclonal antibodies to recombinant (r)Lep d 2 were produced with standard hybridoma technique. Dust samples from 393 households were analysed for allergen content by two-site ELISA methods.

RESULTS

A two-site Lep d 2 ELISA was developed with a detection limit of 0.09 microg/g. The assay was highly reproducible and levels of Lep d 2 showed a strong correlation with the number of Lepidoglyphus mites (r(s): 0.7; P = 0.0002). Lep d 2 was detected in 20% of the homes; levels ranged from 0.09 to 1.7 microg/g of dust. Der p 1 was recorded in 59% of the samples, ranging from 0.055 to 139 microg/g, and Der f 1 and Der 2 in 40% and 50% of the samples, ranging from 0.055 to 24.5 microg/g and 24.3 microg/g, respectively. Dermatophagoides allergens were significantly higher in mattresses than in carpets (P < 0.0001), but this difference was not observed with Lep d 2. A strong relationship between immunoglobulin (Ig)E to rLep d 2 and asthma (OR = 10.4) and rhinoconjunctivitis (OR = 7.5) was seen. Furthermore, sensitization to D. pteronyssinus was significantly associated with asthma (OR: 13.7) and rhinoconjunctivitis (OR: 5.7).

CONCLUSION

When assessing mite allergen exposure in rural homes, not only the Der p 1, Der f 1 and Der 2 allergens, but also the Lep d 2 allergen should be taken into consideration.

Correlation between asthma and climate in the European Community Respiratory Health Survey

The European Community Respiratory Health Survey, performed during 1991-1993, found a remarkable geographical variability in the prevalence of asthma and asthma-like symptoms in individuals aged 20-44 yr. The highest values occurred in the English-speaking centers. In the present investigation, the ecological relationship between climate and symptom prevalence was evaluated in the 48 centers of the European Community Respiratory Health Survey. Meteorological variables were derived from the Global Historical Climatology Network and were averaged over an 11-yr period (i.e., 1980-1990). Respiratory symptom prevalence was directly related to temperature in the coldest month and was related inversely to the temperature in the hottest month. Warm winters and cool summers are features of oceanic climate found in most English-speaking centers of the European Community Respiratory Health Survey (i.e., England, New Zealand, and Oregon). In conclusion, climate can account for significant geographic variability in respiratory symptom prevalence.

House dust mite, cat, and cockroach allergen concentrations in daycare centers in Tampa, Florida

BACKGROUND

Allergen exposure in early childhood is a risk factor for sensitization and the development of asthma. Studies performed in Europe, New Zealand, and Singapore indicated the presence of indoor allergens in childcare centers and schools. However, the importance of indoor allergens in daycare centers in humid and warm regions of the world is not known.

OBJECTIVE

To measure total mite counts, Der p 1, Der f 1, Fel d 1, and Per a 1 allergens in dust samples and mite allergen airborne concentrations in daycare centers in Tampa, Florida, United States.

METHODS

Twenty daycare centers were surveyed for mite, cat, and cockroach allergens in Tampa, FL. One dust and two air samples (one during the day and one during the night) were collected in each center. Dust samples were extracted and analyzed for mite (Der p 1 and Der f 1), cat (Fel d 1), and cockroach (Per a 1) allergens. Mite airborne allergen concentrations were analyzed by RAST inhibition and expressed in standardized mite allergen units per m3 of air (AU/m3).

RESULTS

Mites were identified in 15 samples, and concentrations ranged from 10 to 1,200 mites/g (298 +/- 355.2). The most prevalent mite species was Dermatophagoides pteronyssinus ( Der p 1). Der p 1 and/or Der f 1 were detected in 10 daycare centers. Der p 1 was detected in eight centers and ranged from I to 21.8 microg/g of dust (5.4 +/- 6.9); Der f 1 was detected in 3 centers and ranged from 0.2 to 2.1 microg/g of dust (1.3 +/- 0.9). Per a 1 and Fel d 1 were detected in all centers in small quantities; Per a 1 ranged from 8 to 1,806 ng/g (263.1 +/- 449.7) and Fel d 1 from 0.2 to 120 U/g of dust (16.6 +/- 31.7), respectively. Airborne mite allergen was detected in 18 centers and ranged from 0.01 to 2.7 AU/m3 during the day (0.2 +/- 0.6) and from 0.01 to 0.12 AU/m3 during the night (0.06 +/- 0.03), P = 0.001.

CONCLUSIONS

Mite, cat, and cockroach allergens are present in daycare centers in Tampa, FL. Mite allergen concentrations exceeded levels that have been associated with sensitization and symptoms in allergic subjects in 40% of these centers.

Standardization of in vitro methods

IgE-antibody analysis is a major diagnostic procedure and a primary tool in allergological research. The determination of sensitization frequencies and antibody concentrations against allergens of defined sources provides critical information for the estimation of the relative importance of food and environment in clinical allergy. True quantitation is essential and requires assay designs providing allergen excess and mass unit calibration. Standardized and reproducible methods show geographic and culture dependent differences between patient populations and contribute to the quality of diagnosis and treatment of allergic disease.

Allergic rhinoconjunctivitis, eczema, and sensitization in two areas with differing climates

In this 5-year follow-up study we compared the prevalence of allergic rhinoconjunctivitis, eczema, and sensitization, in relation to several background factors, in two Swedish regions (Göteborg and Kiruna). In Göteborg, a city on the southwest coast, the climate is mild and humid. Kiruna is a town north of the Arctic Circle. Questionnaire replies and results of interviews were collected from all 412 7-8-year-old children of a population-based sample (203 in Göteborg and 209 in Kiruna); in addition, 192 children from Göteborg and 205 from Kiruna were skin-prick tested for sensitization to common aero-allergens. After 5 years, at 12-13 years of age, almost all of the initial study cohort were re-investigated. At follow-up the prevalence of allergic rhinoconjunctivitis was 17%, eczema 23%, and sensitization 32%. Allergic rhinoconjunctivitis and eczema were as common in Göteborg as in Kiruna, whereas sensitization was far more common in Kiruna. Children born during the pollen season had allergic rhinoconjunctivitis less often -- and were sensitized to pollen and animal protein less often -- than those born during the rest of the year. Sensitization to birch pollen, cat protein, and horse protein was less common in children living in Göteborg, the region with the highest frequency of cat ownership and horseback riding, and with the longest birch-pollen season. The girls were more commonly horseback riders but the boys were more often sensitized to horses. The results reinforce our previous findings: indoor climate may affect the development of sensitization and allergic diseases, to some extent independently; and if exposure to antigen is unavoidable, high doses might be better than low doses.

Influence of early and current environmental exposure factors on sensitization and outcome of asthma in pre-school children

BACKGROUND

Exposure to furred pets in early life has been considered to increase the risk of allergic sensitization and consequent development of asthma later in children. However, recently, it has been suggested that early exposure to pets prevents sensitization. The aim of this study was to evaluate the importance of early exposure to pets and other environmental risk factors in asthmatic children.

METHODS

This is a follow-up study after 2 years of a previously investigated group of 193 asthmatic children, aged 1-4 years. The study was completed by 181 children, who were clinically examined; serum IgE antibodies were also measured and a questionnaire was answered.

RESULTS

Children with reported exposure to cats during the first 2 years of life were more likely to have developed sensitization to cat by 4 years of age than unexposed children. High levels of cat allergen (Fel d 1> or =8 microg/g dust) were associated with an increased risk of sensitization to cat and, in combination with tobacco smoke, also with the development of more severe asthma.

CONCLUSION

In young asthmatic children, early exposure to cat and tobacco smoke increased the risk of allergic sensitization and further development of more severe asthma later in childhood.

Prenatal risk factors of wheezing at the age of four years in Tanzania

BACKGROUND

A study was undertaken to assess the interactions between prenatal exposures, early life infections, atopic predisposition, and allergen exposures in the development of wheezing up to the age of 4 years in a tropical region of Africa.

METHODS

The study subjects comprised children born at the district hospital in Ifakara, Tanzania during a 1 year period who were participating in a trial of iron supplementation and malaria chemoprophylaxis during the first year of life and followed for up to 4 years. From this group of subjects, 658 (79%) participated in the interview at 18 months and 528 (64%) in a second interview at 4 years. Wheezing was measured with the ISAAC questionnaire. A hospital based inpatient and outpatient surveillance system was set up to document all attendance by study children for any cause, including episodes of clinical malaria and lower respiratory tract infections. Total IgE levels and malaria parasites were measured in maternal and cord blood. Total IgE was also measured at 18 months of age. Indoor environmental levels of Der p I and Fel d I were determined using an enzyme linked immunosorbent assay at the same time as the interview at the age of 18 months.

RESULTS

The prevalence of wheezing at 4 years is common in Ifakara (14%, range 13-15%). The presence of malaria parasites in cord blood (odds ratio, OR = 6.84, 95% CI 1.84 to 24.0) and maternal asthma (OR = 8.47, 95% CI 2.72 to 26.2) were positively associated with wheezing at the age of 4 years, and cord blood total IgE was negatively associated (OR = 0.24, 95% CI 0.07 to 0.85) (all p<0.05). Parasitaemia at birth was not related to total IgE levels in cord blood (p=0.6). Clinical episodes of malaria during infancy were not associated with wheezing, and nor were levels of indoor aeroallergens.

CONCLUSION

These findings suggest that events occurring during pregnancy may play a role in the future appearance of wheezing, although the results must be interpreted with caution because of the small numbers studied.

Sensitization and exposure to pet allergens in asthmatics versus non-asthmatics with allergic rhinitis

In sensitized subjects with allergic rhinitis (AR) or asthma, allergen exposure provokes symptoms. Among non-asthmatics with AR, an association between allergen sensitization, pollen season and lower airway inflammation has been demonstrated. Our aims were to compare AR and asthma with regard to patterns of allergen sensitization, the degree of airway hyperresponsiveness (AHR) and levels of exhaled nitric oxide (ENO). Finally, we wanted to relate our findings to previous or current exposure to household pets. Four hundred and thirty-one adolescents with different clinical phenotypes were randomly selected from a large-scale epidemiological survey. They were investigated with allergy screening, measurements of ENO and a methacholine bronchoprovocation test. Sensitization to pet allergens (cat, dog and horse) was associated with increased AHR and ENO both in asthmatics and non-asthmatics with AR. The risk of being sensitized to cat allergens was significantly reduced in those who had kept cats vs. those who had never kept them. Keeping dogs or horses did not influence the risk of being sensitized to the respective allergens. Only in steroid-naive, non-smoking asthmatics, a trend towards increased ENO in those sensitized and exposed to cat or dog allergens was seen. Although sensitization towards pet allergens was associated with inflammation in the lower airways irrespective of clinical phenotype, keeping pets did not increase the risk of being sensitized to pet allergens.

Levels of house-dust-mite allergen in homes of nonallergic people in Pavia, Italy

BACKGROUND

HDM distribution varies between geographic areas and may be affected by housing characteristics. We quantified Der p 1 and Der f 1 and assessed the relationships between their levels and housing characteristics in homes of nonallergic subjects.

METHODS

Der f 1 and Der p 1 were measured by ELISA in dust samples from living-room floors and mattresses of 44 homes of nonallergic subjects in Pavia. Information about household characteristics was obtained by questionnaire.

RESULTS

Der p 1 and Der f 1 concentrations (microg/g dust, median) were 0.34 and 7.8 on mattresses, and 0.15 and 0.83 on living-room floors. Higher Der f 1 levels on mattresses were associated with synthetic pillows (P<0.05), and (only when expressed as microg/m2) with bedding washing temperature of < or = 60 degrees C (P<0.05). Der f 1 levels were higher on the living-room floors of homes located on lower (< or =first) floors (P<0.05). Good correlations were found between Der p 1 and Der f 1 expressed as microg/g dust and microg/m2 on both mattresses and living-room floors.

CONCLUSIONS

In homes of nonallergic subjects in northern Italy, Der f 1 exceeded the threshold for sensitization in a high proportion of mattress samples.

Synthetic pillows contain higher levels of cat and dog allergen than feather pillows

The use of non-feather pillows has increased over the last few decades. Recently, we found significantly higher levels of dust mite allergens in synthetic pillows than in feather ones. This study investigated the levels of pet allergens in feather and synthetic pillows. Dust samples were collected from 14 pairs of pillows (consisting of one synthetic fibre-filled and one feather-filled). Each pair of pillows had been on the same bed for at least 2 years. The pillows were vacuumed for 1 min on each side through a 355-microm diameter mesh onto a 5-microm vinyl filter, producing a sample of fine dust. Samples were extracted, and cat (Fel d 1) and dog (Can f 1) allergens determined using monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA). Results were expressed both as total amount of allergen recovered and concentration of allergen per unit weight (ng/g). Total levels of pet allergens were significantly higher in the synthetic pillows (Fel d 1: 6.7-fold difference [95% CI 1.5-29.7], p=0.01; Can f 1: 8-fold difference [95% CI 1.6-39.5], p=0.01). Similarly, when the results were expressed as ng/g, synthetic pillows contained significantly more allergens than feather pillows (Fel d 1: 3.7-fold difference [95% CI 1.3-10.1], p=0.01); Can f 1: 4.4-fold difference [95% CI 1.5-13.2], p=0.01). We have therefore demonstrated that synthetic pillows contain significantly more pet allergens than feather pillows, supporting the view that tightly woven encasements surrounding feather pillows act as a barrier for allergens.

Asthma in children: prevalence, treatment, and sensitization

This study compares the prevalence of asthma and sensitization in children from two Swedish regions with different climates: Göteborg on the southwest coast and Kiruna in the northern inland, north of the Arctic Circle. The 412 children of a population-based sample, 203 in Göteborg and 209 in Kiruna, were investigated at age 7-8 and 12-13 years. Questionnaire reports and interviews were obtained from all children at 7-8 years of age, and 192 children were skin-prick tested for common aeroallergens in Göteborg and 205 in Kiruna. At the follow-up, 5 years later, almost all the children were re-investigated. The prevalence of asthma, wheeze, and sensitization had increased with increasing age during the follow-up period. The questionnaire reports revealed that the prevalence of asthma was 8.5% at 12-13 years of age. All children who in the questionnaire reported current asthma, were using asthma medication. The interviews indicated that the prevalence of a clinically significant asthma might be even higher, reaching approximately 12%. Asthma and wheeze were as common in Göteborg as in Kiruna despite large differences in prevalence of sensitization. Sensitization, and especially sensitization to animals, was far more common in Kiruna than in Göteborg. This study shows that asthma and wheeze are increasingly prevalent even in school age children and that sensitization does not necessarily reflect the prevalence of asthma in a population.

Culture conditions for the detection of allergen-specific T-cell reactivity in cord blood: influence of cell number

Raised T-cell proliferation of cord blood mononuclear cells (CBMC) in response to various ingestant and inhalant allergens has been reported in newborns, suggesting a prenatal allergen contact. In general, for in vitro proliferation assays a concentration of 50 x 10(3) or 100 x 10(3) cells/well are used. The aim of this study was to analyze whether cell concentration influences T-cell reactivity in cord blood cells and to study differences of T-cell reactivity triggered by inhalant and ingestant allergens. CBMC from 51 neonates (34 females: 22 with and 29 without a family history of allergy, i.e. FH+ or FH-) were incubated with interleukin-2 (IL-2), beta-lactoglobulin (beta-LG), ovalbumin (OVA), house dust mite allergen Dermatophagoides pteronyssinus (Der p 1), and timothy grass allergen Phleum pratense (Ph1 p 1) for 7 days. The cell concentration ranged from 6.25 x 10(3) to 100 x 10(3) cells/well. Proliferation was assessed by incorporation of [3H]-thymidine and was expressed as counts per minute (c.p.m.). In unstimulated cells, a decreasing cell concentration paralleled a steep drop of background activity. In response to IL-2, a decreasing cell concentration led to a slow decrease of c.p.m. The corresponding mean stimulation indices (SI) were 9, 32, 77, 47, and 21 for 100 x 10(3), 50 x 10(3), 25 x 10(3), 12.5 x 10(3), and 6.25 x 10(3) cells/well, respectively. In addition, the highest number of positive proliferative responses to specific allergens were obscured at lower cell concentrations. For beta-LG, the maximal number of positive responses were obtained between 25 x 10(3) (n = 44) and 12.5 x 10(3) (n = 46) cells/well, for OVA at 25 x 10(3) (n = 3) cells/well, for Der p 1 at 50 x 10(3) (n = 5) cells/well, and for Ph1 p 1 between 25 x 10(3) and 12.5 x 10(3) (n = 5) cells/well. Positive proliferation in at least one of the tested assays was observed in 100% of samples in response to beta-LG, in 22% in response to Ph1 p 1, and in 14% in response to OVA and Der p 1. T-cell reactivity did not differ between samples of newborns with or without a family history of atopy. Therefore, sensitivity of T-cell proliferation measurement is highly influenced by background proliferation of unstimulated cells. Hence, proliferation assays with lower cell numbers unmask T-cell reactivity in response to ingestant and inhalant allergens. We suggest the use of concentrations of 12.5 x 10(3)-50 x 10(3) cells/well in proliferation experiments.

Indoor environment, atopy and the risk of the asthma in children in New Zealand

The objective of this study was to examine the relationship between the indoor environment, atopy and asthma in 7-9-year-old children. Cases and controls were randomly selected from children who participated in the International Study of Asthma and Allergies in Childhood (ISAAC) in Wellington, New Zealand. Cases were children with a previous diagnosis of asthma and current medication use (n = 233) and controls were children with no history of wheezing and no diagnosis of asthma (n = 241). Information was recorded about the indoor environment during the first year of life and currently. Dust was sampled from floors and beds and Der p 1 and Fel d 1 measured using enzyme-linked immunosorbent assays. Skin-prick tests were performed with eight common allergens. Sensitization to Dermatophagoides farinae (OR = 3.19; 95% CI 1.74-5.84), Dermatophagoides pteronyssinus (OR = 2.06; 95% CI 1.16-3.65) and cat (OR = 3.89; 95% CI 1.06-14.30) were independently associated with current asthma. The use of a sheepskin in the first year of life (OR = 1.91; 95% CI 1.11-3.33) was also independently associated with current asthma but current Der p 1 levels showed no association with current asthma. Exposures in early life may be more important than current exposures in determining asthma at age 7-9 years. Prospective studies are needed in New Zealand to determine the relative importance of early life exposures to Der p 1 and other risk factors for asthma.

Mite fauna in the home and sensitivity to house-dust and storage mites

In search of potential new indoor allergen sources, all mites in dust from homes of 55 asthmatic children living in three climatic regions in Sweden were counted and identified by light microscope. Antibodies of the IgE class against three house-dust mites and three storage mites were measured in corresponding serum samples. Mites were found in all but two homes from the northernmost area, where levels also were lower than in the other regions. The highest mite densities were most often found in bedrooms (50%) and living rooms (40%). Mite density was increased in homes with high humidity and was higher in bungalows than in flats. House-dust mites predominated in the south and storage mites in the east central area, particularly in kitchens and bathrooms. Mite-density and IgE-antibody levels against house-dust mites were significantly associated. The same association applied to storage mites. Other species numbered around 100 mites/g dust in some homes. Microscopy helps to identify potentially important mites. Analysing home dust only for house-dust mites will underestimate mite exposure. Storage mites may be as relevant to sensitivity as house-dust mites. As other species occasionally were found in high numbers, their relevance should also be assessed.

Indoor allergen exposure in west and East Germany: a cause for different prevalences of asthma and atopy?

West and East Germans have been living in two different political systems for 40 years. These two populations have become a classic epidemiological example for the hypothesis that lifestyle changes accompanying the industrial and economic development of modern societies are responsible for an increase in the prevalence of atopic diseases. A higher prevalence of atopic sensitization, asthma, and hay fever was found in young West Germans after the unification. It has been hypothesized that this phenomenon was at least partially due to the installation of insulating windows and central heating systems in Western homes, favoring the growth of microorganisms like mites and moulds and increasing indoor allergen exposure. This review summarizes studies that have investigated reservoir concentrations of indoor allergens in public buildings and private homes in East and West Germany. Whereas a higher prevalence of atopic sensitization in West Germans was found for nearly all tested allergens (cat, mite, pollen), allergen exposure was higher only for cat allergens, but probably not for mite and cockroach allergens or moulds. The published data do not support the view that the differences in specific sensitization are caused by differences in the exposure to specific allergens.

Relevance of allergens from cats and dogs to asthma in the northernmost province of Sweden: schools as a major site of exposure

BACKGROUND

The prevalence of asthma in the northernmost region of Sweden has been estimated at 6% to 8% in spite of the very dry climate. The causes of the increase in asthma are not clear, but conditions are unfavorable for dust mite growth, and domestic animals are thought to be the primary source of indoor allergens.

OBJECTIVES

We sought to investigate the relationship between asthma, exposure, and sensitization in Northern Sweden, with a focus on the role of schools.

METHODS

Serum was collected from 110 asthmatic children, 55 children with symptoms of asthma but no established diagnosis, and 63 control children (age, 7 and 8 years). Total IgE and specific IgE to 7 allergens were measured. Dust samples were collected from the classrooms of 7- and 8-year-old children in 22 schools from Kiruna and Luleâ, Sweden. For comparison, dust was also collected from 24 homes in Kiruna and 2 schools in Virginia in the United States.

RESULTS

Serum IgE antibody assays on 165 children with respiratory symptoms confirmed that there was a high degree of sensitization to cat, dog, and birch in Northern Sweden. Cat and dog allergens were present in almost all of the school samples in Sweden. By contrast, dust mite and cockroach allergens were generally unmeasurable. The highest levels of cat and dog allergens were found in samples from desks and chairs. Cat and dog allergen levels in the schools were comparable with but higher than those in the homes without pets. The schools in Virginia had similar allergen levels, except that samples from this humid region also had significant mite allergen.

CONCLUSIONS

In this climate the primary sensitization associated with asthma is to cat dander and dog dander but also to birch pollen. Mite and cockroach allergens were not present in the dust samples, and sensitization to these allergens was not significant. The schools appear to be a major site of exposure to cat and dog allergens. These results are relevant both to an understanding of the reasons for the increase in asthma in this region and to any proposal to reduce exposure to allergens.

Mite allergen (Der p 1) levels in houses of children with atopic dermatitis: the relationship with allergometric tests

Several studies, in particular in adult groups, have evaluated the involvement of mites in the pathogenesis of atopic dermatitis (AD). This still remains controversial. The objective of this study was to determine the level of house dust mites (HDMs) in the beds of a group of children with AD and correlate these levels with their allergometric assessment. Forty-one children with AD underwent allergometric tests (prick test, patch test and radioallergosorbent test, RAST) and the concentration levels of HDMs in their homes were evaluated. Our data show that about half of the children (51%) with AD presented Dermatophagoides pteronyssinus positivity (prick test and/or RAST and/or patch test). Dust was collected in the period October-November from the children's beds, by the same two operators, using a dust-collection device. The dust mite level was tested by an enzyme-linked immunosorbent assay with antibody against Der p 1 allergen. Ten children (24%) presented a Der p 1 concentration > 2 microgram/g of dust (the value assumed to be a risk level for sensitization), 20 (49%) between 0.1 and 2 microgram/g and 11 (27%) < 0.1 microgram/g of dust. In the group with the highest Der p 1 concentration (> 2 microgram/g dust) nine children (90%) presented an allergometric D. pteronyssinus sensitivity, the difference with the other two groups being statistically significant at P < 0.018. The results of the present study show that the highest HDM concentrations were observed in the group with an allergometric D. pteronyssinus positivity (prick test and/or RAST and/or patch test). It is hypothesized that a higher HDM concentration may elicit D. pteronyssinus IgE sensitization and delayed hypersensitivity in children with AD.

House dust mite exposure as a risk factor for asthma: benefits of avoidance

There is a dose-response relation between the level of exposure to house dust mite allergen and the risk of acquiring sensitization to this allergen as well as the risk of developing asthma. This relation is apparent at levels of exposure below 10 microg/g. In communities where nearly all houses have house dust mite allergen levels above this threshold, all susceptible individuals will be affected, and the relation to house dust mite exposure will not be apparent. Although these observational data would suggest that reducing exposure to house dust mite allergen should lessen the risk of developing sensitization and asthma, definitive evidence from randomized controlled trials is not yet available. Of the many clinical trials of house dust mite avoidance as therapy for asthma, only a few have produced sustained, substantial reductions in allergen levels in the bed. These effective interventions all included allergen-impermeable encasement of mattresses along with other strategies. In most trials where allergens levels were successfully reduced, there were clinical benefits for patients with asthma.

Epidemiological analyses of the relationship between environmental pollution and asthma

Epidemiological studies performed on children and young adults indicate that the prevalence of asthma has increased over the past decades in a number of countries. Since genetic determinants alone are unlikely to explain these findings, environmental factors are expected to have an important impact on the prevalence of this disease. Environmental pollution, among many other factors, may play a role in the initiation and manifestation of asthma. However, there is little epidemiological evidence for a causal association between the classical major outdoor air pollutants, such as SO2 or particulate matter, and asthma. Evidence for an association between air pollution from motor vehicles and asthma is still controversial. Thus the indoor environment and other environmental determinants--including lifestyle factors--are likely to be more important as causes of asthma. Epidemiological studies are able to evaluate the effects of environmental factors on the health of human populations in their usual environments. In addition, they can measure associations between long-term environmental exposures and health outcomes. By using refined techniques for exposure and disease assessment, as well as time and cost-effective study designs, environmental epidemiology will increase the knowledge about the role of pollution as a possible cause of asthma.

Environmental allergens and childhood asthma

Exposure to allergens has been shown to lead to sensitization and to the subsequent development of airway hyperresponsiveness in genetically predisposed individuals. Increasing interest is being devoted to mechanisms for the prevention of allergen sensitization and asthma development. Primary prevention (avoiding the sensitization to allergens) requires a large effort as the majority of atopic sensitizations occur in children with no demonstrable risk at the birth. Secondary prevention (deterrence of disease expression despite prior IgE sensitization) requires methods for detecting the population at risk by means of large population screening. Tertiary prevention (minimizing the morbidity for those who already have the disease) may be achieved by allergen avoidance, which has been demonstrated to effectively decrease inflammation in symptomatic patients.

Role of the indoor environment in determining the severity of asthma

Allergen exposure can confound the management of asthma. To understand the potential mechanisms by which allergens increase the steroid requirements in atopic asthmatics, we examined the effects of allergens on glucocorticoid receptor (GCR) binding affinity and glucocorticoid (GC) responsiveness of peripheral blood mononuclear cells (PBMC) from atopic asthmatics. A significant reduction (p < 0.001) in the GCR binding affinity (Kd) was observed in ragweed-allergic asthmatics during ragweed pollen season compared with PBMC obtained before and after ragweed season. In vitro effects of allergen on PBMC GCR Kd were also examined by incubating PBMC from atopic asthmatics with allergen (ragweed and cat) versus Candida albicans. GCR binding affinity was significantly reduced after incubation with ragweed (p < 0.001) or cat allergen (p < 0.001) compared with baseline or C. albicans stimulation. This effect was limited to atopic asthmatics in that in vitro cat allergen incubation for 48 h failed to significantly alter GCR binding affinity in nonasthmatic, atopic individuals. These allergen-induced reductions in GCR binding affinity also rendered the PBMC less sensitive to the inhibitory effects of hydrocortisone and dexamethasone on allergen-induced proliferation (p < 0.01). To test the hypothesis that allergen-induced alterations in GCR binding affinity were cytokine-induced, we examined the effects of interleukin-2 (IL-2) and IL-4 neutralization using anticytokine antibodies. Addition of both anti-IL-2 and anti-IL-4 antibodies resulted in a significant (p < 0.001) inhibition of allergen-induced alterations in GCR binding affinity. Furthermore incubation with cat allergen induced significantly higher concentrations of IL-2 (p = 0.03) and IL-4 (p = 0.02) by PBMC from atopic as compared with nonatopic subjects. Our current observations suggest that allergen exposure may contribute to poor asthma control by reducing GCR binding affinity in mononuclear cells. This appears to be mediated through IL-2 and IL-4. These findings may have important implications for novel approaches to the treatment of poorly controlled asthma.

Environmental assessment of Dermatophagoides mite-allergen levels in Sweden should include Der m 1

The major allergen of Dermatophagoides microceras, Der m 1, as well as the allergens of D. pteronyssinus and D. farinae, Der p 1 and Der f 1, were analyzed in the homes of 111 asthmatic children in three climatic regions in Sweden. The numbers and species of mites were determined by microscopy, and circulating IgE antibodies against mites were measured. Der f 1 was the predominant house-dust-mite (HDM) allergen, Der p 1 the least often found, and Der m 1 represented 31% of the allergen load. However, in the Linköping area, Der m 1 was the major HDM allergen (58%). Mite counts and allergen levels correlated well. Current exposure to HDM allergens at home was associated with the serum IgE antibody response to HDM in the children with no threshold level. Of the children with IgE antibodies against HDM, 67% reacted to all three mites. Mite sensitization rates were marginally increased (7%) by the addition of IgE analysis of D. microceras to the routine analysis of IgE antibodies against D. pteronyssinus and D. farinae. Thus, Der m 1 may be an important HDM allergen and should be considered when HDM exposure data are assessed in areas with a climate like that of Sweden.