The rising trend in allergic illness: which environmental factors are important?

Allergic Rhinitis and Atopy in 18-Year-Old Students

Background

The aim of this study was to investigate the prevalence of allergic rhinitis and atopy in adolescents and whether air pollution in their schools contributed to allergic sensitization.

Methods

Analyses were performed in 1992–1994 on 511 18-year-old students at four schools and on the indoor air and floor dust of their classrooms. The students underwent skin-prick tests (SPTs) and a nasal lavage and answered a computer-based questionnaire containing questions on allergy and nasal symptoms.

Results

Atopy, defined as at least one positive SPT response, was found among 37% of the students, with no difference between students of the four schools, regardless of whether the data were adjusted for gender, hereditary disposition to allergy, and smoking habits. The number of students who had positive SPT and reported nasal symptoms when exposed to possible allergens, which were found among 35%, did not differ between the schools. No correlation was found between the prevalence of atopic individuals and the levels of different indoor air pollutants in the schools.

Conclusion

The prevalence of allergic rhinitis among adolescents is very high and suggests that it is, at least at the time of our study and in comparison with other studies, still increasing. Our results indicate that the indoor air and floor dust at the schools of the students do not contribute to allergic sensitization.

One-year longitudinal study of young apprentices exposed to airway occupational sensitizers

BACKGROUND

The prevalence of diagnosed asthma and wheezing in young subjects is increasing; among environmental risk factors, occupational exposure can play a relevant role.

STUDY OBJECTIVES

The purpose of the study was to evaluate the effects of occupational exposure to a large variety of irritants and/or sensitizers on the incidence of respiratory symptoms and pulmonary function impairment in a group of young apprentices during the first year of work exposure, and to determine the prevalence of asthma-like symptoms and the role of different risk factors (gender, smoking habit, atopy and occupational exposure) in this young population.

DESIGN AND METHODS

We studied 448 young apprentices at the first pre-employment evaluation with a standardized questionnaire, spirometry and skin prick tests; in 244 of them clinical and functional evaluation was repeated after 1 year exposure to respiratory irritants or sensitizers.

RESULTS

At the first examination, males had higher prevalence of attacks of shortness of breath with wheeze, diagnosis of asthma, smoking habit and atopy than females. At the second examination there was no significant increase in the prevalence of respiratory symptoms. However, incident cases for cough, phlegm, wheezing, shortness of breath with wheeze (SOBWHZ) and asthma were all higher than remittent cases. Incidence of respiratory symptoms was associated with atopy and smoking habit.

CONCLUSIONS

Respiratory symptoms slightly increase over 1 year occupational exposure to sensitizers or irritants. The loss at the follow-up of subjects with higher smoking habit suggests a small "health worker effect" and could underestimate the effect of occupational exposure in apprentices.

Acellular pertussis vaccine protects against exacerbation of allergic asthma due to Bordetella pertussis in a murine model

The prevalence of asthma and allergic disease has increased in many countries, and there has been speculation that immunization promotes allergic sensitization. Bordetella pertussis infection exacerbates allergic asthmatic responses. We investigated whether acellular pertussis vaccine (Pa) enhanced or prevented B. pertussis-induced exacerbation of allergic asthma. Groups of mice were immunized with Pa, infected with B. pertussis, and/or sensitized to ovalbumin. Immunological, pathological, and physiological changes were measured to assess the impact of immunization on immune deviation and airway function. We demonstrate that immunization did not enhance ovalbumin-specific serum immunoglobulin E production. Histopathological examination revealed that immunization reduced the severity of airway pathology associated with sensitization in the context of infection and decreased bronchial hyperreactivity upon methacholine exposure of infected and sensitized mice. These data demonstrate unequivocally the benefit of Pa immunization to health and justify selection of Pa in mass vaccination protocols. In the absence of infection, the Pa used in this study enhanced the interleukin-10 (IL-10) and IL-13 responses and influenced airway hyperresponsiveness to sensitizing antigen; however, these data do not suggest that Pa contributes to childhood asthma overall. On the contrary, wild-type virulent B. pertussis is still circulating in most countries, and our data suggest that the major influence of Pa is to protect against the powerful exacerbation of asthma-like pathology induced by B. pertussis.

Synthesis and pharmacological investigation of novel 1-substituted-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones as a new class of H1-antihistaminic agents

A series of novel 1-substituted-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones 7 were synthesized by the cyclization of 2-hydrazino-3-phenylquinazolin-4(3H)-one 6 with various one carbon donors. The starting material 2-hydrazino-3-phenylquinazolin-4(3H)-one 6, was synthesized from aniline 1 by a novel innovative route. When tested for their in vivo H(1)-antihistaminic activity on conscious guinea pigs all the test compounds protected the animals from histamine induced bronchospasm significantly, whereas the compound 1-methyl-4-phenyl-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-one 7b (percentage protection 70.7%) was found to be equipotent with the reference standard chlorpheniramine maleate (percentage protection 71%). These compounds show negligible sedation ( approximately 5%) when compared to the reference standard (26%). Hence they could serve as prototype molecules for future development.

Whole-cell pertussis vaccine protects against Bordetella pertussis exacerbation of allergic asthma

The prevalence of asthma and allergic disease has increased in many countries and there has been speculation that immunization promotes allergic sensitization. Bordetella pertussis infection exacerbates allergic asthmatic responses. We investigated whether whole-cell pertussis vaccine (Pw) enhanced or prevented B. pertussis induced exacerbation of allergic asthma. Groups of mice were immunized with Pw, infected with B. pertussis and/or sensitized to ovalbumin. Immunological, pathological and physiological changes were measured to assess the impact of Pw immunization on immune deviation and airway function. Pw immunization modulated ovalbumin-specific serum IgE production, and reduced local and systemic IL-13 and other cytokine responses to sensitizing allergen. Histopathological examination revealed Pw immunization reduced the severity of airway pathology and decreased bronchial hyperreactivity to methacholine exposure. Pw does not enhance airway IL-13 and consequently does not enhance but protects against the exacerbation of allergic responses. We find no evidence of Pw contributing to allergic asthma, but rather provide evidence of a mechanism whereby whole-cell pertussis vaccination has a protective role.

Risk factors for atopic eczema in school children

OBJECTIVES: to study risk factors related to atopic eczema (AE) in school children of São Paulo. METHODS: 1972 parents or guardians of 6-7 years old children in the Southern Central area of São Paulo answered to a written questionnaire (standardized questionnaire of the International Study of Asthma and Allergies in Childhood plus a complementary questionnaire regarding family history of asthma and allergies, and exposure to environmental allergens). AE was defined by the presence of an itchy rash in the last year. Risk factors were analyzed through logical regression. RESULTS: the following factors were significantly associated with AE: history of maternal (OR: 4.1; 95%CI: 2.4 to 7.1) and paternal eczema (OR: 2.6; 95%CI: 1.4 to 5.0), dust in the child's bedroom (OR: 1.6; 95%CI: 1.1 to 2.4), lower maternal education (OR: 1.7; 95%CI: 1.1 to 2.7), rhinitis fever (OR: 1.7; 95%CI: 1.1 to 2.9) and wheezing in the last year (OR: 1.9; 95%CI: 1.2 to 2.8). CONCLUSIONS: our data suggest that AE has a specific pattern of inheritance. The presence of dust in the child's bedroom was the single environmental risk factor found. Diagnose of other allergic diseases, as well as the presence of recent symptoms were strongly associated with AE in children.

Synthesis and H1-Antihistaminic Activity of Some Novel 1-Substituted-4-(3-methylphenyl)-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones

A series of novel 1-substituted-4-(3-methylphenyl)-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-ones were synthesized by the cyclization of 2-hydrazino-3-(3-methylphenyl) quinazolin-4(3H)-one with various one carbon donors. The starting material 2-hydrazino-3-(3-methylphenyl)quinazolin-4(3H)-one, was synthesized from 3-methylaniline by a novel innovative route. When tested for their in vivo H(1)-antihistaminic activity on conscious guinea pigs, all the test compounds protected the animals from histamine induced bronchospasm significantly, whereas the compound 1-methyl-4-(3-methylphenyl)-1,2,4-triazolo[4,3-a]quinazolin-5(4H)-one II was found to be equipotent (percent protection 70.0%) with the reference standard chlorpheniramine maleate (percent protection 71%). Compound II show negligible sedation (7%) when compared to chlorpheniramine maleate (25%). Hence it could serve as prototype molecule for further development as a new class of H(1)-antihistamines.

Age-specific relationship between CD14 and atopy in a cohort assessed from age 8 to 25 years

CD14 influences postnatal switching of T helper cell responses. CD14 C-159T has been associated with altered CD14 and IgE levels in cross-sectional studies. Identifying whether associations vary with age requires data from children of the same age followed longitudinally over many years. In this study, an unselected population with extensive longitudinal data was used to test the hypothesis that CD14 C-159T was associated with early-onset atopy. A total of 305 subjects were assessed on up to seven occasions between ages 8 and 25 years by questionnaire, histamine challenge, and skin prick test. For atopy, airway hyperresponsiveness (AHR), and wheeze, each subject was classified as having early onset, late onset, or no disease onset during follow-up. Compared with subjects with -159CT and -159TT, subjects with -159CC had an odds ratio of 2.2 (p = 0.018) for early-onset atopy and an odds ratio of 2.6 (p = 0.019) for early-onset AHR. Cross-sectional analysis showed increased prevalence of -159CC in subjects with atopy and AHR in childhood but not adulthood. These data suggest that the influence of CD14 -159C on the atopic phenotype may be age specific, exerting an effect during midchildhood, which is no longer apparent by early adulthood.

Changing approaches to asthma management in Australia: effects on asthma morbidity

Asthma is an important public health issue in Australia and is responsible for significant morbidity and mortality in the community. Recognition of the impact of asthma on the health of Australians, and the apparent failure of new medications to reduce mortality and hospital admission rates resulted in a major review by the stakeholders in asthma care. This led to new approaches to asthma management based on strategic use of asthma medications and the development of the Asthma Management Plan (AMP). The AMP drew together current understanding of asthma to develop a simple stepwise approach to management that could be readily applied in patient management. The National Asthma Campaign (NAC), a coalition of the major stakeholders in asthma care, was launched in 1990 to lead the dissemination of the AMP. In association with other organisations interested in asthma care in Australia, the NAC has developed the AMP, and co-ordinated a decade of education and advocacy about asthma that targeted doctors, health professionals and the general public. These activities have been successful in raising awareness about asthma in the community. However, recent research, while demonstrating the continued uptake of written asthma action plans for asthma and decrease in use of inhaled bronchodilator medications, reported a decrease in use of preventive therapy by people with asthma. These activities have had a sustained impact on asthma-related health outcomes with mortality at the lowest level since 1960 and a decline in hospital readmission rates. This is useful information because there is sound evidence that the prevalence and possibly severity of asthma in children has increased. However, review of management in primary care and among people who present to emergency services with acute asthma suggest that many people continue to manage their asthma poorly. Continued education is needed to build on the progress that has been made. There are opportunities to do this through efforts to integrate general practitioners into the wider health system through the formation of Divisions of General Practice. Recognition of asthma as a health priority area at a national level will help to enhance and maintain awareness of the public health importance of asthma and facilitate the further development of the initiatives begun during the last decade or more.

Environmental allergens and irritants in schools: a focus on asthma

As part of the Partners in School Asthma Management Program, environmental data were collected from 385 rooms in 60 elementary schools in southeast Texas, using an Environmental Observation Checklist and a Q-TRAK Indoor Air Quality Monitor. Dust samples for allergen analysis were collected from floors, carpets, and area rugs in 80 classrooms in a subset of 20 schools. CO2 levels > 1,000 ppm were found in 86% of rooms; 69% had indoor humidity above recommended levels. Der p I dust mite allergen levels > 2,000 ng/g were present in 20% of rooms, but only 2.5% of rooms had Der f I mite allergen levels exceeding recommended tolerances. Detectable levels of cockroach allergen (Bla g II) were found in all schools (median 5.5 ng/g), with 10% of rooms over the recommended threshold. Almost two-thirds of classrooms had mold spore counts > 10,000 col/g (median, 14,400 col/g; range, 2,000-52,000 col/g).

Dietary antioxidants and ozone-induced bronchial hyperresponsiveness in adults with asthma

Ozone exposure aggravates asthma, as has been demonstrated in both controlled exposures and epidemiologic studies. In the current double-blind crossover study, the authors evaluated the effects of dietary antioxidants (i.e., 400 IU vitamin E/500 mg vitamin C) on ozone-induced bronchial hyperresponsiveness in adult subjects with asthma. Seventeen subjects were exposed to 0.12 ppm of ozone or to air for 45 min during intermittent moderate exercise. Bronchial hyperresponsiveness was assessed with 10-min sulfur dioxide (i.e., 0.10 ppm and 0.25 ppm) inhalation challenges. Subjects who were given dietary antioxidants responded less severely to sulfur dioxide challenge than subjects given a placebo (i.e., forced expiratory volume in the 1st sec: -1.2% vs. 4.4%, respectively; peak flow: +2.2% vs. -3.0%, respectively; and mid-forced expiratory flow: +2.0% vs. -4.3%, respectively). Effects were more pronounced when subjects were grouped by response to sulfur dioxide at the screening visit. The results suggest that dietary supplementation with vitamins E and C benefits asthmatic adults who are exposed to air pollutants.

Effect of allergist intervention on patient-centered and societal outcomes: allergists as leaders, innovators, and educators

Atopic disorders, which afflict millions of Americans and hundreds of millions worldwide, are at epidemic levels with concomitant increases in morbidity and mortality. Environmental and lifestyle changes over the past three to five decades are proposed causes for this pandemic and as such present major burdens to reverse. The scope of allergy practice bridges directly on this challenge. Allergy as a specialty is a major leader in developing effective strategies to confront this epidemic. Allergists have made major contributions to the understanding of the risk factors, immunology, pathophysiology, immunomodulation, and prevention of atopic and immunologic disorders. Allergist epidemiologists and clinicians have helped develop and implement national and international guidelines in the recognition, management, and prevention of asthma and rhinitis. Allergist clinical researchers are active in (1) outcomes research that demonstrates convincingly the value of allergy as a specialty in asthma, allergic rhinitis, anaphylaxis, drug and food allergy, and other atopic disorders, (2) National Institutes of Health clinical trials that will form the basis for the future treatment of asthma and allergic disease, and (3) pharmaceutical trials that evaluate new, effective, and safe medication to treat atopic disease. Allergist educators, comprising academic and practicing allergists, supported by allied health professionals, national associations, and affiliated lay organizations, provide comprehensive education to fellows, residents, colleague physicians, media, the public, and patients. Documentation of the value of allergists in improving patient-centered and societal outcomes in their core domain, allergy, is the appropriate final topic contribution in the important series "New millennium: The conquest of allergy."

Aspergillus and other moulds in the air of Kuwait

A one-year survey was carried out to study the aerial prevalence of Aspergillus species and other moulds in the outdoor and indoor environments of Kuwait. Petri plates containing rose-Bengal medium were exposed for 20 minutes twice a month using a six-stage Andersen air sampler at the pre-determined sites. The exposed plates were incubated at 28 degrees C +/- 1 degree C up to 5 days and colonies were enumerated and identified by colonial and microscopic morphology. The data revealed that Aspergillus species were the predominant component (27.7%) of the outdoor aerospora of Kuwait and A. fumigatus alone accounted for 21.3% of the total aspergilli. In contrast, Cladosporium species formed the major component of the indoor aerospora (22.8%), followed by Aspergillus species (20.9%), Penicillium species (14.6%), and Bipolaris species (10.6%). A comparison of the fungi recorded in the outdoor and in the indoor air revealed that Aspergillus, Alternaria and Fusarium were significantly higher in the outdoor environment, whereas Cladosporium, Penicillium, and Bipolaris were significantly higher in the indoor environment. The relative prevalence of Aspergillus species and other moulds in the outdoor and indoor air of Kuwait was as follows: A. fumigatus 5.9 and 9.8%, A. flavus 4.9 and 3.9%, other aspergilli 16.8 and 7.0%, Alternaria species 19.8 and 7.9%, Cladosporium species 13.7 and 22.8%, Penicillium species 7.6 and 14.6%, and other moulds 31.2 and 34.1%, respectively. During the study, 25 different genera were identified, indicating a wide diversity in the spectrum of local fungal aerospora. The study provides useful information on the prevalence of allergenic fungi in the outdoor and indoor environments of Kuwait.

The occurrence, recrudescence, and worsening of asthma in a population of young adults: impact of varying types of occupation

OBJECTIVE

To describe the rates of exacerbation of existing asthma and incidence of new disease in Israeli men during military service.

DESIGN

All 17-year-old Israeli nationals are obliged by law to appear at the Israel Defense Forces (IDF) recruiting office for medical examination. The medical history of army recruits was noted during the 30-month period after their induction into the IDF, and medical examinations were performed by pulmonary specialists in all suspected cases of asthma. The duty status of the soldiers in combat units (CUs), maintenance units (MUs), and clerical tasks was related to their asthma status.

RESULTS

Of a total of 59,058 recruits, 1.0% developed asthma during the 30 months of this study; of those in CUs, 1.2% developed asthma; of those in MUs, 0.8% developed asthma; and of those performing clerical tasks, 0.6% developed asthma. The relative risk for developing or worsening of asthma was related to both the preexisting asthma status of the recruit and the environment in which he carried out his military service. The annual incidence of occupational-related asthma in MUs was found to be 800/million: five to six times the rates reported elsewhere.

CONCLUSIONS

Service in CUs was associated with an increased frequency of exacerbation of asthma among recruits with previous disease and with the appearance of disease de novo. "Normal" conscripts with a history of childhood asthma are at a higher risk of developing overt asthma when compared to subjects with no such history. We found a 25% relative excess of incident cases of asthma in soldiers posted in MUs compared to those performing clerical tasks [(0.8 to 0.6%)/0.8%]. This difference is probably attributed to the difference in occupational hazards in these categories. Further studies are needed to determine if this represents the elicitation of underlying preexisting airway lability by new work demands or other environmental conditions, or if this represents a new development of airway lability because of specific immune or nonimmune factors.

The epidemiology of childhood asthma

Variability is the hallmark of childhood asthma. Conceptually defined as variable airflow obstruction, asthma affects individual children through a variety of clinical manifestations. Particular controversy surrounds the nature of wheezing in early infancy and its relationship to atopic asthma of later onset. Asthma prognosis is also highly variable and only to a limited extent predictable by clinical indicators in early childhood. Long-term follow-up studies suggest a complex pattern of remission and relapse as wheezy children are followed through adolescence into adult life. Similarly, the population burden of asthma is highly variable, both over time and between countries. The balance of evidence worldwide suggests a modest but sustained increase in the prevalence of asthma symptoms over the past three decades. Superimposed on this have been larger changes in diagnostic fashion and use of health services for childhood asthma in many countries. There is substantial international variation in the prevalence of asthma symptoms, and marked urban-rural differences have been reported from several African countries. These contrast with the more uniform distribution of the disease within industrialized countries, reflecting its ubiquity in affluent societies.

Changing prevalence of allergic rhinitis and asthma

OBJECTIVE

This review will enable the reader to discuss prevalence, risk factors, and prognosis of allergic rhinitis and asthma.

DATA SOURCES

MEDLINE (PubMed) search using the terms allergic rhinitis, asthma, prevalence, risk factors.

STUDY SELECTION

Human studies published in the English language since 1978, especially studies of relatively large populations in the United States, Great Britain, Australia, and New Zealand, with cross referencing to earlier relevant studies.

RESULTS

Current prevalence of allergic rhinitis at 16 years of age in cohorts of British children born in 1958 and 1970 increased from 12% in the earlier cohort to 23% and in the later cohort. Local surveys of allergic rhinitis at approximately 18 years of age in the United States in 1962 to 1965 disclosed prevalence of 15% to 28%, while the national survey of 1976 to 1980 disclosed a prevalence of 26%. Thus, it is uncertain whether prevalence of allergic rhinitis has changed in the United States based on these limited data. Data from several sources indicate worldwide increases in prevalence of asthma. Annual Health Interview surveys indicate increases in prevalence of asthma in the United States from 3.1% in 1980 to 5.4% in 1994, but prevalence among impoverished inner city children has been much higher. Combined prevalence of diagnosed and undiagnosed asthma among inner city children has been 26% and 27% at 9 to 12 years of age in Detroit and San Diego. Positive family history and allergy are important risk factors for allergic rhinitis and asthma. Prognosis is guarded; allergic rhinitis resolves in only 10% to 20% of children within 10 years, and at least 25% of young adults who have had asthma during early childhood are symptomatic as adults.

CONCLUSION

Increases in prevalence remain unexplained, but avoidance of recognized allergens should reduce the prevalence of allergic rhinitis and asthma.

Airborne house dust elicits a local lymph node reaction and has an adjuvant effect on specific IgE production in the mouse

Indoor suspended particulate matter (SPM) consists of many different types of particles, the vast majority of which are less than 2.5 microm in diameter. An important question is how these particles, being inhalable, contribute to asthma and respiratory symptoms. One possibility is that these particles have an adjuvant effect on the immune response and increase the IgE production, or cause a non-specific irritation in the airways, contributing to bronchial hyper-responsiveness. In this study, the adjuvant activity of indoor SPM on the response to the model allergen ovalbumin (OA) in BALB/c mice was investigated, using the popliteal lymph node (PLN) assay. The adjuvant activity on the local lymph node response was determined by measuring the PLN weight, cell numbers and cell proliferation, and the adjuvant activity on the IgE production by measuring the levels of serum IgE specific to OA. SPM was found to give a significant PLN response, both when injected alone and together with OA. SPM was also found to enhance the production of specific IgE to OA when injected together with OA, after reinjection with OA, compared with immunisation with OA alone.

The home environment and asthma symptoms in childhood: two population based case-control studies 13 years apart

BACKGROUND

Prevalence surveys of asthma and/or wheezing among all children aged between 7 1/2 and 8 1/2 attending state and private schools in the London Borough of Croydon were conducted in February 1978 and February 1991. Two population based case-control studies drawn from the survey responders were used to investigate the association between childhood wheeze and characteristics of the home environment and to assess whether changes in these characteristics between 1978 and 1991 may have contributed to an increase in the population prevalence of wheeze among school children.

METHODS

Information on exposure to potential indoor environmental risk factors was obtained from parents by home interview and compared between cases-that is, children with frequent (> or = 5) or in-frequent (1-4) attacks of asthma or wheezing in the past 12 months- and controls, with adjustment for study. Changes in exposure over time were assessed by comparing control groups.

RESULTS

Between 1978 and 1991 the population prevalence odds of wheeze increased by 20% (OR 1.20; 95% CI 1.04 to 1.39). Change in parental smoking, gas cooking, pet ownership, and central heating did not appear to explain the rise. Use of non-feather pillows was positively associated with childhood wheeze even after adjusting for other risk factors and after re-coding from non-feather to feather cases thought to have changed pillow in response to symptoms (OR 1.54; 95% CI 1.13 to 2.10). The proportion of control children reportedly using non-feather pillows was 44% in 1978 and 67% in 1991.

CONCLUSIONS

Increased use of non-feather pillows was the only domestic indoor exposure studied which appeared to explain a modest rise in prevalence of wheeze from 1978 to 1991. Our analysis attempts to address behavioural change in response to the child's symptoms but an artifact arising from lifelong avoidance of feather bedding in atopic families cannot be entirely discounted.

Evidence for the increase in asthma worldwide

This chapter reviews the evidence that asthma is increasing and that changes in exposure to environmental risk factors may explain the increase. Although asthma is difficult to define for epidemiological studies, the prevalence of asthma as measured by the questionnaire definitions 'asthma ever diagnosed' and 'wheeze ever' is large and increasing. In all countries where serial studies using the same methods have been undertaken over the last 20 years, an increase in wheezing illness in children and adolescents has been recorded but there are insufficient data to determine whether the disease is increasing in adults. Despite the recorded increases, there remains a large difference in the prevalence of asthma between populations, with high rates of wheezing illness in Australasia and low rates in villages in poor countries. The male to female ratio for the occurrence of asthma remains at about 1.5 in children, 1.0 in late adolescence and less than 1.0 in adults, when more females than males have symptoms. The risk factors for childhood asthma are atopy (positive skin tests), parental asthma, allergen load, respiratory infections, some aspects of diet and an 'affluence' factor. There is some evidence for an increase in the prevalence of atopy in children but this may be due to earlier acquisition of atopy. Changes in the other risk factors have not been documented. The evidence for changes in indoor allergen loads, in diet, in the severity and nature of respiratory infections, and in 'affluence' is indirect and comes from a number of small studies rather than from serial epidemiological studies. It seems unlikely that a single, environmental risk factor has changed dramatically worldwide. Rather, a number of lifestyle changes may have combined to cause the disease to be expressed in children who, in previous times, were immunologically protected from developing asthma, perhaps by their T helper cell phenotype, or were not exposed to high allergen levels.

Indoor mite allergens in patients with respiratory allergy living in Porto, Portugal

We investigated the levels of mite allergens (Der p 1, Der f 1, Der 2, and Lep d 1) in dust samples from the homes of 59 patients with asthma, 36 sensitized to house-dust mites (HDM) and 23 to grass pollen (controls), living in Porto, northern Portugal. The relationship between exposure and sensitization to HDM and the influence of housing conditions on mite-allergen levels were also evaluated. Der p 1 (median 9.2 micrograms/g) and Der 2 (4.6 micrograms/g) were the main allergens, while Der f 1 and Lep d 1 levels were always < 1 microgram/g dust and undetectable in 11% and 47% of samples, respectively. All HDM-sensitized asthmatics were exposed to Der p 1 levels > 2 micrograms/g and their homes contained significantly higher levels of Der p 1 (median 12.5 vs 6.4 micrograms/g; P = 0.008) and Der 2 (6.2 vs 3.0 micrograms/g; P = 0.004) when compared to the control group. A significant correlation was observed between the exposure to Der p 1 and the wheal area at skin testing with the Dermatophagoides pteronyssinus (Dp) extract (P = 0.01) as well as with serum specific IgE levels to Dp (P = 0.03). Patients with higher levels of serum specific IgE (> or = 17.5 HRU/ml) were also more frequently exposed to Der p 1 levels > or = 10 micrograms/g (P = 0.002). Old homes, presence of carpets, and signs of dampness were conditions associated with significantly higher levels of mite allergens. In conclusion, we found high levels of Der p 1 and Der 2 particularly in the homes of HDM-sensitized patients and we confirm the relationship between exposure and sensitization to HDM, assessed by both in vivo and in vitro methods. In additional to a favorable outdoor climate, we found in our region housing conditions propitious to mite growth, suggesting that specific geographic characteristics must also be taken into account for the correct planning of mite-avoidance measures.

New insights into risk factors of asthma

The prevalences of bronchial asthma in the Asia-Pacific region range from 0 to 24% and appear to be increasing in some countries. The increased prevalence of asthma may be related to the urbanization of these countries or areas. Risk factors relating to the development of asthma are multiple and complex. These include: Predisposing or genetic factors: (atopy and bronchial hyperresponsiveness; BHR) that increase an individuals susceptibility. Longitudinal studies in children have shown that BHR precedes asthma in some individuals. A gene governing BHR is located near a major locus that regulates serum IgE levels on chromosome 5 q. An additional gene that determines the specificity of the immune response located in the human leukocyte antigen complex (HLA) may govern the specificity of the immune response to common aeroallengens in some individuals. Causal Factors: inhaled allergens are the most important causal factors of asthma, which include indoor allergens (domestic mites, animal, cockroach and fungus allergens), domestic mites being the most common potential allergen, and outdoor allergens (pollens from trees, grasses and weeds). Owing to the geographic location and different sensitivity to allergen between races, allergens vary from area to area. Certain drugs, food and food additives are also the cause of asthma attack. Contributing factors: smoking is an important trigger and a serious problem in most Asian-Pacific countries. Air pollution in particular sulfur dioxide (SO2), nitrogen dioxide (NO2) and respirating particles are common contributing factors. Very low concentration of SO2 (0.5 ppm) can cause bronhospasm in asthmatics. A combination of low concentration of SO2 and NO2 often encountered in heavy traffic further enhances the airway responsiveness to inhaled allergen. In addition, respiratory virus infection is closely associated to the development of asthma in childhood.