Does early exposure to cat or dog protect against later allergy development?

Comprehensive US Statewide Smoke-Free Indoor Air Legislation and Secondhand Smoke Exposure, Asthma Prevalence, and Related Doctor Visits: 2007-2011

OBJECTIVES

We evaluated the impact of comprehensive statewide smoke-free indoor air laws on secondhand smoke (SHS) exposure, asthma prevalence, and asthma-related doctor visits.

METHODS

We used the 2007-2011 Behavioral Risk Factor Surveillance System data sets. We employed a paired t test to determine whether comprehensive statewide smoke-free indoor air laws reduced SHS exposure. We performed weighted logistic and Poisson regressions to obtain likelihood of reporting asthma symptoms and incidence rate ratio (IRR) of doctor visits owing to severe asthma symptoms.

RESULTS

After such laws were enacted, people in states with comprehensive smoke-free indoor air laws had a lower level of SHS exposure (P < .01), decreased odds of reporting current asthma symptoms (adjusted odds ratio [AOR] = 0.57; 95% confidence interval [CI] = 0.51, 0.63), and a decreased frequency of doctor's visits owing to severe asthma symptoms (IRR = 0.80; 95% CI = 0.69, 0.92) than did their counterparts in fully adjusted models.

CONCLUSIONS

Comprehensive statewide smoke-free indoor air laws appear to be effective in reducing SHS exposure and improving asthma outcomes. Regulations requiring smoke-free indoor environments and public areas are beneficial, and smoke-free indoor air laws should be enforced in all states.

Microbiota in allergy and asthma and the emerging relationship with the gut microbiome

Asthma and atopy, classically associated with hyper-activation of the T helper 2 (Th2) arm of adaptive immunity, are among the most common chronic illnesses worldwide. Emerging evidence relates atopy and asthma to the composition and function of the human microbiome, the collection of microbes that reside in and on and interact with the human body. The ability to interrogate microbial ecology of the human host is due in large part to recent technological developments that permit identification of microbes and their products using culture-independent molecular detection techniques. In this review we explore the roles of respiratory, gut, and environmental microbiomes in asthma and allergic disease development, manifestation, and attenuation. Though still a relatively nascent field of research, evidence to date suggests that the airway and/or gut microbiome may represent fertile targets for prevention or management of allergic asthma and other diseases in which adaptive immune dysfunction is a prominent feature.

Contributing factors to the development of childhood asthma: working toward risk minimization

Asthma is the most common chronic disease in childhood, and considerable research has been undertaken to find ways to prevent its development and reduce its prevalence. For such interventions to be successful, risk factors for asthma emergence should be identified and clearly defined. Data are robust for some of them, including atopy, viral infections and exposure to airborne irritants, whereas it is less conclusive for others, such as aeroallergen exposure and bacterial infections. Several interventions for asthma prevention, including avoidance and pharmacotherapy, have been attempted. However, most of them have furnished equivocal results. Various issues hinder the establishment of risk factors for asthma development and reduce the effectiveness of interventions, including the complexity of the disease and the fluidity of the developing systems in childhood. In this review, we revisit the evidence on pediatric asthma risk factors and prevention and discuss issues that perplex this field.

Allergy in children in hand versus machine dishwashing

BACKGROUND AND OBJECTIVE

The hygiene hypothesis stipulates that microbial exposure during early life induces immunologic tolerance via immune stimulation, and hence reduces the risk of allergy development. Several common lifestyle factors and household practices, such as dishwashing methods, may increase microbial exposure. The aim of this study was to investigate if such lifestyle factors are associated with allergy prevalence.

METHODS

Questionnaire-based study of 1029 children aged 7 to 8 years from Kiruna, in the north of Sweden, and Mölndal, in the Gothenburg area on the southwest coast of Sweden. Questions on asthma, eczema, and rhinoconjunctivitis were taken from the International Study of Asthma and Allergies in Childhood questionnaire.

RESULTS

Hand dishwashing was associated with a reduced risk of allergic disease development (multivariate analysis, odds ratio 0.57; 95% confidence interval: 0.37-0.85). The risk was further reduced in a dose-response pattern if the children were also served fermented food and if the family bought food directly from farms.

CONCLUSIONS

In families who use hand dishwashing, allergic diseases in children are less common than in children from families who use machine dishwashing. We speculate that a less-efficient dishwashing method may induce tolerance via increased microbial exposure.

Green areas around homes reduce atopic sensitization in children

Background

Western lifestyle is associated with high prevalence of allergy, asthma and other chronic inflammatory disorders. To explain this association, we tested the ‘biodiversity hypothesis’, which posits that reduced contact of children with environmental biodiversity, including environmental microbiota in natural habitats, has adverse consequences on the assembly of human commensal microbiota and its contribution to immune tolerance.

Methods

We analysed four study cohorts from Finland and Estonia (n = 1044) comprising children and adolescents aged 0.5–20 years. The prevalence of atopic sensitization was assessed by measuring serum IgE specific to inhalant allergens. We calculated the proportion of five land-use types – forest, agricultural land, built areas, wetlands and water bodies – in the landscape around the homes using the CORINE2006 classification.

Results

The cover of forest and agricultural land within 2–5 km from the home was inversely and significantly associated with atopic sensitization. This relationship was observed for children 6 years of age and older. Land-use pattern explained 20% of the variation in the relative abundance of Proteobacteria on the skin of healthy individuals, supporting the hypothesis of a strong environmental effect on the commensal microbiota.

Conclusions

The amount of green environment (forest and agricultural land) around homes was inversely associated with the risk of atopic sensitization in children. The results indicate that early-life exposure to green environments is especially important. The environmental effect may be mediated via the effect of environmental microbiota on the commensal microbiota influencing immunotolerance.

Novel Risk Factors for Allergic Rhinitis in Korean Elementary School Children: ARCO-kids Phase II in a Community

Purpose

Allergic rhinitis (AR) is a multifactorial disease whose genetic and environmental risk factors have been studied for decades. Many pediatric studies have pointed out the familial history of allergy, hygiene hypothesis, breast-feeding, pet ownership, and diets as risk factors of AR. However, most of factors are still up for debate. This preliminary report aimed to confirm the known risk factors and find the novel risk factors for AR in the Korean pediatric population.

Methods

A bi-seasonal, winter and summer, study in 2 elementary schools included all students whose parents completed the questionnaire of medical and social histories, quality of life, infant and early-childhood history, and the living styles. Skin prick tests and endoscopic examinations were conducted on all participants.

Results

Among total 1,020 children, 338 participants had AR. The multivariate logistic regression analysis highlighted 6 factors: male gender (OR, 2.10; 95% CI, 1.32-3.33), older age (1.65; 1.03-2.65), previous history of allergic conjunctivitis (14.25; 4.99-40.74), asthma (2.73; 0.96-7.76) and pneumonia (0.39; 0.19-0.82), and an hour increase in daily playing time (0.90; 0.80-1.00).

Conclusions

Lack of pneumonia in early childhood and short playing time are newly found risk factors for Korean pediatric AR in this study confirming male gender, older age and previous history of allergic conjunctivitis and asthma as the risk factors.

Reprint of: Perinatal and early childhood environmental factors influencing allergic asthma immunopathogenesis

BACKGROUND

The prevalence of asthma has increased dramatically over the past several decades. While hereditary factors are highly important, the rapid rise outstrips the pace of genomic variation. Great emphasis has been placed on potential modifiable early life exposures leading to childhood asthma.

METHODS

We reviewed the recent medical literature for important studies discussing the role of the perinatal and early childhood exposures and the inception of childhood asthma.

RESULTS AND DISCUSSION

Early life exposure to allergens (house dust mite (HDM), furred pets, cockroach, rodent and mold), air pollution (nitrogen dioxide (NO2), ozone (O3), volatile organic compounds (VOCs), and particulate matter (PM)) and viral respiratory tract infections (Respiratory syncytial virus (RSV) and human rhinovirus (hRV)) has been implicated in the development of asthma in high risk children. Conversely, exposure to microbial diversity in the perinatal period may diminish the development of atopy and asthma symptoms.

Allergy to furry animals: New insights, diagnostic approaches, and challenges

The prevalence of allergy to furry animals has been increasing, and allergy to cats, dogs, or both is considered a major risk factor for the development of asthma and rhinitis. An important step forward in the diagnosis of allergy to furry animals has been made with the introduction of molecular-based allergy diagnostics. A workshop on furry animals was convened to provide an up-to-date assessment of our understanding of (1) the exposure and immune response to the major mammalian allergens, (2) the relationship of these responses (particularly those to specific proteins or components) to symptoms, and (3) the relevance of these specific antibody responses to current or future investigation of patients presenting with allergic diseases. In this review research results discussed at the workshop are presented, including the effect of concomitant exposures from other allergens or microorganisms, the significance of the community prevalence of furry animals, molecular-based allergy diagnostics, and a detailed discussion of cat and dog components.

Risk factors affecting asthma prevalence in adolescents living in Istanbul, Turkey

BACKGROUND

Asthma is one of the most important diseases of childhood. The aim of this study was to evaluate the prevalence of asthma symptoms and risk factors affecting asthma.

METHODS

In a cross-sectional study design, 9991 children, aged 13-14 years in 61 primary schools in 32 districts of Istanbul were evaluated. Asthma prevalence among the children was assessed using the ISAAC protocol.

RESULTS

In our study, a total of 10,894 questionnaires were distributed to 13-14 years old children, and of these 9991 questionnaires were suitable for analysis with an overall response rate of 91.7%. The rates of wheeze ever, wheezing in last 12 months and lifetime doctor diagnosed asthma prevalence were 17.4%, 9.0%, and 11.8%, respectively. There were 4746 boys (47.9%) and 5166 girls (52.1%) with M/F ratio of 0.92. Atopic family history, fewer than three siblings living at home, tonsillectomy or adenoidectomy history, consumption of fermented foods, mixed pickles, margarine and meat were found to be associated with an increased asthma risk. Use of paracetamol in the last 12 months, consumption of fruit and animal fats acted as a protective factor against asthma. The Mediterranean-style diet was not associated with the prevalence of asthma.

CONCLUSIONS

Lifetime doctor diagnosed asthma prevalence was found to be 11.8% in 13-14 year olds. History of tonsillectomy and/or adenoidectomy and consumption of fermented foods, mixed pickles, margarine and meat may increase the symptoms of asthma. Usage of paracetamol and consumption of animal fats may be investigated as a protective factor against asthma.

Early life environmental predictors of asthma age-of-onset

Prevention strategies that delay the onset of asthma may improve clinical outcomes. To identify early life environmental exposures associated with asthma age-of-onset and potential genetic modifiers of these exposures, we studied 1085 subjects with physician-diagnosed asthma and disease onset at or after age two. Subjects reported retrospectively on their exposure to 17 environmental factors before the age of two. The presence of individual or combinations of these early life exposures was then tested for association with variation in asthma age-of-onset. For exposures significantly associated with age-of-onset, we tested if 26 single nucleotide polymorphisms (SNP) with an established association with allergic disease significantly modified the effect of the exposure. Five environmental exposures were significantly associated with variation in asthma age-of-onset after correction for multiple testing: carpet at home (P = 6 × 10⁻⁵), a serious chest illness (P = 10⁻⁴), father a cigarette smoker (P = 6 × 10⁻⁴) and direct exposure to father's smoking (P = 3 × 10⁻⁴). Individuals with early childhood asthma onset, between the ages of two and six, were 1.4-fold (CI 1.1–1.9) more likely to report having lived in a house with carpet and 2.1-fold (CI 1.3–3.5) more likely to report suffering a serious chest illness before the age of two, than asthmatics with later disease onset. We further found these individual risks to increase to 3.2-fold (CI 1.7–6.0) if carpet exposure and suffering a serious chest illness co-occurred before age two. Paternal smoking exposures were less likely to be reported by asthmatics with early when compared to later disease onset (OR 0.5, CI 0.3–0.7). There were no significant SNP interactions with these environmental exposures after correction for multiple testing. Our results suggest that disease onset in individuals at a high-risk of developing asthma can potentially be delayed by avoiding exposure to carpet at home and preventing serious chest illnesses during the first 2 years of life.

Perinatal and early childhood environmental factors influencing allergic asthma immunopathogenesis

BACKGROUND

The prevalence of asthma has increased dramatically over the past several decades. While hereditary factors are highly important, the rapid rise outstrips the pace of genomic variation. Great emphasis has been placed on potential modifiable early life exposures leading to childhood asthma.

METHODS

We reviewed the recent medical literature for important studies discussing the role of the perinatal and early childhood exposures and the inception of childhood asthma.

RESULTS AND DISCUSSION

Early life exposure to allergens (house dust mite (HDM), furred pets, cockroach, rodent and mold), air pollution (nitrogen dioxide (NO(2)), ozone (O(3)), volatile organic compounds (VOCs), and particulate matter (PM)) and viral respiratory tract infections (Respiratory syncytial virus (RSV) and human rhinovirus (hRV)) has been implicated in the development of asthma in high risk children. Conversely, exposure to microbial diversity in the perinatal period may diminish the development of atopy and asthma symptoms.

The prevalence of asthma diagnosis and symptoms is still increasing in early adolescents in Turkey

BACKGROUND

This study was performed to evaluate the time trends in prevalence of asthma and related factors in Denizli, Turkey.

METHODS

Two cross-sectional surveys were performed, 6 years apart (2002 and 2008) using the ISAAC protocol, in the 13-14 age groups and comparisons were made between the results.

RESULTS

Lifetime prevalence of wheeze, 12 month prevalence of wheeze, and the prevalence of wheeze after exercise in the previous 12 months were significantly increased respectively from 10.2% to 13.4% (POR = 1.37, 95%CI = 1.18-1.58, p < 0.001), from 5.0% to 6.2% (POR = 1.26, 95%CI = 1.02-1.55, p = 0.016) and from 9% to 10.2% (POR = 1.15, 95%CI = 0.98-1.35, p = 0.046) in 2008 study. Doctor diagnosed asthma prevalence also increased significantly from 2.1% to 12.9 (POR = 6.80, 95%CI = 5.22-8.85, p < 0.001). Prevalence of sleep disturbed by wheeze in the last 12 months; but, never woken with wheezing (POR = 1.62, 95%CI = 1.26-2.09, p = < 0.001) and less than one night per week (POR = 1.58, 95%CI = 1.06-2.36, p = 0.013) were significantly increased in 2008 study. Severe attacks of wheeze limiting speech in the last year was increased from 1.3% to 2.2% (POR = 1.67, 95%CI = 1.14-2.43, p = 0.004). The number of wheeze attacks in the previous 12 months was increased significantly for 4-to-12 attacks (POR = 1.54, 95%CI = 1.03-2.32, p = 0.02) in 2008 study. However, prevalence of waking with cough in the last 12 months did not change. While history of family atopy and domestic animal at home were found as significant risk factors for asthma in 2002 study, male gender, history of family atopy and stuffed toys were found significant in 2008.

CONCLUSIONS

The prevalence of asthma symptoms were increased in Denizli. History of family atopy, male gender and stuffed toys were important risk factors for asthma in 2008.

Determinants of sensitization to allergen in infants and young children

Atopic sensitization is a complex phenomenon that changes dynamically with age throughout childhood; its prevalence increases with age in young children. Additionally, with increasing age, the prevalence of sensitization to inhalant allergens and the prevalence of polysensitization to allergens increase. It is also well established that the development of atopic sensitization is the result of a complex interplay of genetic and environmental factors. However, there is considerable heterogeneity in the literature in terms of the effect of different environmental exposures in young children on the subsequent risk of atopic sensitization and allergic diseases. Previous studies on the relationship, in early life, between pet ownership, sex, exposure to secondhand smoke, exposure to traffic-related air pollution components, and atopic sensitization have yielded different results. Recent studies have highlighted the importance of gene-environment interactions, especially during early childhood, on the risk of subsequent atopic sensitization and allergic diseases. Therefore, pediatricians should consider the genetic and environmental determinants of atopic sensitization in infants and young children when diagnosing and treating patients with allergic diseases. Determining ways in which early exposure to these risk factors in young children may be reduced could be beneficial in preventing the likelihood of developing atopic sensitization.

Immune responses to inhalant Mammalian allergens

In Europe and the USA, at least one person in four is exposed every day to inhalant allergens of mammalian origin, a considerable number is regularly exposed for professional reasons and almost everyone is occasionally exposed to inhalant allergens from pets or domestic animals. The production of IgE to these inhalant allergens, often complicated by asthma and rhinitis, defines the atopic status. However, the immune response to these allergens largely imprints the cellular immune compartment and also drives non-IgE humoral immune responses in the allergic and non-allergic population. During the recent years, it has become clear that IgE antibodies recognize mammalian allergens that belong to three protein or glycoprotein families: the secretoglobins, the lipocalins, and the serum albumins. In this article, we review the humoral and cellular immune responses to the major members of these families and try to define common characteristics and also distinctive features.

Changes in cat specific IgE and IgG antibodies with decreased cat exposure

BACKGROUND

Current understanding of the effects of reducing exposure to cat allergens is limited. It has also become clear that there are different forms of immune response to cat allergens.

OBJECTIVE

To investigate changes in skin tests and cat specific IgG and IgE antibodies when students from a home with a cat move to a college dormitory.

METHODS

Ninety-seven college students participated in a prospective study that consisted of allergy skin prick testing and serum measurement of IgE and IgG antibodies to cat at the beginning and end of one academic year in college. A subgroup returned for follow-up at the end of 2 years.

RESULTS

Among 97 students, 33% had IgG antibodies to Fel d 1 but no evidence of sensitization, 25% had positive skin test results and/or serum IgE antibodies, and 42% had negative skin test results and no detectable serum antibodies. Among the non-cat sensitized students with IgG antibodies, the titers decreased during 8 months (P = .002). Titers of IgG4 to Fel d 1 also decreased (P < .001). Among the sensitized students, no change in IgE antibodies to cat occurred in 8 months (P = .20), whereas Fel d 1 specific IgG antibodies decreased (P < .001). Thus, ratios of IgG to IgE decreased highly significantly (P = .007). Among the students with negative skin test results who returned for follow-up (n = 56), none developed positive skin test results or serum IgE antibodies.

CONCLUSION

Under conditions of marked decrease in exposure, no participants developed new-onset sensitization. Among the individuals sensitized at study entry, there were major decreases in the ratio of IgG to IgE.

What are the main environmental exposures associated with elevated IgE in Cuban infants? A population-based study

OBJECTIVE

Immunoglobulin E (IgE) plays a key role in allergy disease pathogenesis, but little is known about the environmental factors associated with higher IgE levels in infants. The aim of this study was to determine the risk factors for elevated serum total IgE infants living in Havana.

METHODS

Eight hundred and seventy-seven infants provided blood samples. Data on allergic disease symptoms and a wide range of exposures were collected.

RESULTS

The median IgE was 35 IU/ml (interquartile range 13-96). The risk of having an IgE level above the median was higher for children who had been breastfed for 4 months or more (adjusted odds ratio (OR) 1.28; 95% confidence interval (CI): 1.02-1.61) and for children who reported cockroaches in their home (OR 1.30; 95% CI: 1.03-1.63). The risk was lower for children whose mother was in paid employment (OR 0.73; 95% CI: 0.54-0.97 compared with those who did not), for children living in homes where gas and electricity were used for cooking (OR 0.45; 95% CI: 0.32-0.62 compared with electricity only) and for children with domestic pets at birth (OR 0.83; 95% CI: 0.70-1.00). There was no association between paracetamol use and serum IgE levels.

CONCLUSIONS

Associations between gas fuel use and maternal employment indicate that IgE levels in early life are lower in children who may be living in relative affluence. The discrepancy in the effect of early exposure to pets or cockroaches may reflect differences in these allergens, or be confounded by relative affluence. Further investigation of this cohort will determine how these effects translate into the expression of allergic disease in later life.

Prevalence of and risk factors for the development of atopic dermatitis in schoolchildren aged 12-14 in northwest Croatia

BACKGROUND

Atopic dermatitis is a common allergic disorder. A multifactorial background for atopic dermatitis has been suggested, with genetic as well as environmental factors influencing disease development. Our aim was to estimate the prevalence rate and associated factors for atopic dermatitis in northern Croatia using the methods of the internationally standardised ISAAC protocol.

METHODS

The study was undertaken among 12-14-year-old schoolchildren. Data were collected using standardised ISAAC written questionnaire Phase One and some selected questions from the ISAAC supplementary questionnaire completed by parents.

RESULTS

A total of 2887 children participated in the study. Estimated lifetime (ever) prevalence rate of atopic dermatitis symptoms was 7.55% and estimated 12-month prevalence rate was 5.75%. The factors found to be associated to the symptoms of atopic dermatitis ever were: positive family atopy, female gender, sleeping on feather pillow and contact with pets after age of seven, and to the symptoms in the past 12 months were: positive family atopy, female gender, sleeping on feather pillow, parasite infestation, and contact with pets in the first year of life.

CONCLUSIONS

The results of our study show that northern Croatia is a region with moderate prevalence rates of atopic dermatitis. Following risk factors were family atopy, female gender and sleeping on feather pillow. Because of controversial results of previous studies conducted on the same topic further investigations should be made.

Children's residential exposure to selected allergens and microbial indicators: endotoxins and (1→3)-β-D-glucans

OBJECTIVES

The study was aimed at assessment of exposure to endotoxins, (1→3)-β-D-glucans and mite, cockroach, cat, dog allergens present in settled dust in premises of children as agents which may be significantly correlated with the occurrence of allergic symptoms and diseases in children.

MATERIALS AND METHODS

The study covered 50 homes of one-or two-year-old children in Poland. Samples of settled dust were taken from the floor and the child's bed. The levels of (1→3)-β-D-glucans (floor), endotoxins (floor) and allergens of mite, cat, dog and cockroach (floor and bed) were analyzed.

RESULTS

Average geometric concentrations (geometric standard deviation) of endotoxins, (1→3)-β-D-glucans, Der p1, Fel d1, Can f1 and Bla g1 in children homes were on the floor 42 166.0 EU/g (3.2), 20 478.4 ng/g (2.38), 93.9 ng/g (6.58), 119.8 ng/g (13.0), 288.9 ng/g (3.4), 0.72 U/g (4.4) and in their beds (only allergens) 597.8 ng/g (14.2), 54.1 ng/g (4.4), 158.6 ng/g (3.1) 0.6 U/g (2.9), respectively. When the floor was covered with the carpet, higher concentrations of endotoxins, (1→3)-β-D-glucans and allergens (each type) were found in the settled dust (p < 0.05). The trend was opposite in case of allergens (except dog) analyzed from bed dust and significantly higher concentrations were found in the rooms with smooth floor (p < 0.05).

CONCLUSIONS

Among the analyzed factors only the type of floor significantly modified both the level of biological indicators and allergens. The results of this study could be the base for verifying a hypothesis that carpeting may have a protective role against high levels of cockroach, dog and cat allergens.

New insights into the epidemiology of childhood atopic dermatitis

There is a growing desire to explain the worldwide rise in the prevalence of atopic dermatitis (AD). Trend data on the burden of AD suggest that the picture in the developing world may soon resemble that of wealthier nations, where AD affects over 20% of children. This, combined with significant variations in prevalence within countries, emphasizes the importance of environmental factors. Many hypotheses have been explored, from the modulation of immune priming by hygiene, gut microbiota diversity, and exposure to endotoxins through farm animals to the effects of pollution, climate, and diet. The discovery of the filaggrin skin barrier gene and its importance in AD development and severity has brought the focus on gene-environment interactions and the identification of environmental factors that impact on skin barrier function. This article reviews our current understanding of the epidemiology of AD, with an emphasis on the findings reported in the international literature over the last 5 years.

Epidemiology of Respiratory Allergies and Asthma

Asthma has puzzled and confused physicians from the time of Hippocrates to the present day. The word “asthma” comes from a Greek word meaning “panting” (Keeney 1964), but reference to asthma can also be found in ancient Egyptian, Hebrew, and Indian medical writings (Ellul-Micallef 1976; Unger and Harris 1974). There were clear observations of patients experiencing attacks of asthma in the second century and evidence of disordered anatomy in the lung as far back as the seventeenth century (Dring et al. 1689).

Association between birthplace and current asthma: the role of environment and acculturation

OBJECTIVES

We evaluated associations between current asthma and birthplace among major racial/ethnic groups in the United States.

METHODS

We used multivariate logistic regression methods to analyze data on 102,524 children and adolescents and 255,156 adults in the National Health Interview Survey (2001-2009).

RESULTS

We found significantly higher prevalence (P < .05) of current asthma among children and adolescents (9.3% vs 5.1%) and adults (7.6% vs 4.7%) born in the 50 states and Washington, DC (US-born), than among those born elsewhere. These differences were among all age groups of non-Hispanic Whites, non-Hispanic Blacks, and Hispanics (excluding Puerto Ricans) and among Chinese adults. Non-US-born adults with 10 or more years of residency in the United States had higher odds of current asthma (odds ratio = 1.55; 95% confidence interval = 1.25, 1.93) than did those who arrived more recently. Findings suggested a similar trend among non-US-born children.

CONCLUSIONS

Current asthma status was positively associated with being born in the United States and with duration of residency in the United States. Among other contributing factors, changes in environment and acculturation may explain some of the differences in asthma prevalence.

Biomass fuel use and the risk of asthma in Nigerian children

BACKGROUND

Biomass fuel smoke exposure contributes to respiratory infections in childhood, but its association with asthma has not been established. We studied the relationship of biomass fuel use with asthma symptoms and lung function in Nigerian children.

METHODS

A cross-sectional study was performed in 299 village children aged 5-11 years in North Central Nigeria. Data were collected regarding the cooking fuels used and duration of daily smoke exposure in the cooking area. Asthma symptoms were assessed with a modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire, and lung function was assessed with spirometry.

RESULTS

The prevalence of a lifetime history of wheeze was 9.4% (95% CI: 6.3%-13.2%). Fourteen children (4.7%) had airway obstruction (FEV1/FEV6 <85%). Female subjects had lower FEV1 and FEV6 (110 % and 120% percent predicted, respectively) than males (121% and 130%, respectively, P <0.001 for both differences). Advancing age was associated with a relative decline in the predicted value of FEV1 of 7.8 % per year (r = -0.61; P < 0.001). Children in families that used firewood daily did not have a significantly increased likelihood of asthma-related symptoms (OR = 2.36, 95% CI: 0.66-8.44). Similarly, airway obstruction did not differ significantly between children in households that did and did not use firewood daily (mean FEV1/FEV6 of 0.95 and 0.97, respectively; P = 0.41).

CONCLUSION

Reported smoke exposure was not associated with an increased risk of asthma symptoms or airway obstruction. However, lifetime smoke exposure may explain the reduction in spirometric values in female subjects and with advancing age.

High levels of both n-3 and n-6 long-chain polyunsaturated fatty acids in cord serum phospholipids predict allergy development

BACKGROUND

Long-chain polyunsaturated fatty acids (LCPUFAs) reduce T-cell activation and dampen inflammation. They might thereby counteract the neonatal immune activation and hamper normal tolerance development to harmless environmental antigens. We investigated whether fatty acid composition of cord serum phospholipids affects allergy development up to age 13 years.

METHODS

From a population-based birth-cohort born in 1996/7 and followed until 13 years of age (n = 794), we selected cases with atopic eczema (n = 37) or respiratory allergy (n = 44), as well as non-allergic non-sensitized controls (n = 48) based on diagnosis at 13 years of age. Cord and maternal sera obtained at delivery from cases and controls were analysed for proportions of saturated, monounsaturated and polyunsaturated fatty acids among serum phospholipids.

RESULTS

The cord serum phospholipids from subject who later developed either respiratory allergy or atopic eczema had significantly higher proportions of 5/8 LCPUFA species, as well as total n-3 LCPUFA, total n-6 LCPUFA and total LCPUFA compared to cord serum phospholipids from controls who did not develop allergy (P<0.001 for all comparisons). Conversely, individuals later developing allergy had lower proportion of the monounsaturated fatty acid 18∶1n-9 as well as total MUFA (p<0.001) among cord serum phospholipids. The risk of respiratory allergy at age 13 increased linearly with the proportion of n-3 LCPUFA (Ptrend<0.001), n-6 LCPUFA (Ptrend = 0.001), and total LCPUFA (Ptrend<0.001) and decreased linearly with the proportions of total MUFA (Ptrend = 0.025) in cord serum phospholipids. Furthermore, Kaplan-Meier estimates of allergy development demonstrated that total LCPUFA proportion in cord serum phospholipids was significantly associated with respiratory allergy (P = 0.008) and sensitization (P = 0.002), after control for sex and parental allergy.

CONCLUSION

A high proportion of long-chain PUFAs among cord serum phospholipids may predispose to allergy development. The mechanism is unknown, but may involve dampening of the physiologic immune activation in infancy needed for proper maturation of the infant's immune system.

Relationship of dog- and cat-specific IgE and IgG4 levels to allergic symptoms on pet exposure

BACKGROUND

Environmental allergens may induce the generation of allergen-specific IgE (sIgE) and IgG4 (sIgG4). Some studies report an association of sIgG4 to protection against allergic symptoms after exposure to the relevant allergen.

OBJECTIVE

We examined the relationship of dog and cat sIgE and sIgG4 levels to self-reported allergic symptoms on pet contact.

METHODS

Participants 18 years of age in the Detroit Childhood Allergy Study cohort were asked whether they experienced symptoms on exposure to cats and dogs. Serum was assayed for cat and dog sIgE and sIgG4. Geometric means, ratios of cat and dog sIgE, sIgG4, and ratios of sIgG4/sIgE were compared between symptomatic and asymptomatic teens with the use of Wilcoxon rank sum tests. Ratios of sIgG4/sIgE, adjusted for presence of sIgE (≥0.35 kU/mL), were analyzed with logistic regression.

RESULTS

Data on 500 participants were analyzed. Compared with asymptomatic teens, teens symptomatic with cat exposure had higher cat sIgE, sIgG4, and lower ratio of sIgG4/sIgE. Teens symptomatic after dog exposure had higher dog sIgE levels and lower sIgG4/sIgE, but similar levels of sIgG4 compared with asymptomatic participants. Increasing cat and dog sIgG4/sIgE ratios were associated with a lower likelihood of reporting allergic symptoms (cat: adjusted odds ratio, 0.8; 95% CI, 0.6-0.9; dog: adjusted odds ratio, 0.8; 95% CI, 0.7-1.0).

CONCLUSION

sIgG4 levels to cat and dog allergens correlate with lower rates of pet-induced allergic symptoms when interpreted in the context of concomitant sIgE. However, sIgG4 appears to have little utility as an isolated marker to indicate that pet exposure will be well tolerated.

Controversial role of pets in the development of atopy in children

BACKGROUND

Exposure to environmental allergens originating from different sources has been implicated in the sensitization to the respective allergens and development of atopic diseases. Keeping domestic animals is associated with exposure to relevant allergens but there are controversial data whether this exposure promotes or protects from the development of atopy.

DATA SOURCES

We herein reviewed the literature regarding the available data for the exposure to pets (cats and/or dogs) and the development of atopy. For this purpose, we searched the PubMed database.

RESULTS

This review attempts to answer the following questions that arise from the daily practice and the relevant studies, which are: a) is pet keeping associated with sensitization? b) is there an association between keeping pets and the development of asthma, allergic rhinitis and eczema, and, c) what is the underlying mechanism of any possible protective association? Despite the fact that several studies and meta-analyses have been conducted to explore the role of pets in the development of atopy, there are still conflicting pieces of evidence. It seems that there are different effects depending on the type of pets, the time and duration of exposure, and the genetic background of the individual.

CONCLUSION

Further appropriately designed birth cohort studies are needed to explore whether exposure to relevant allergens from pets promotes or protects from the development of atopy.

Infant gut microbiota and the hygiene hypothesis of allergic disease: impact of household pets and siblings on microbiota composition and diversity

BACKGROUND

Multiple studies have demonstrated that early-life exposure to pets or siblings affords protection against allergic disease; these associations are commonly attributed to the "hygiene hypothesis". Recently, low diversity of the infant gut microbiota has also been linked to allergic disease. In this study, we characterize the infant gut microbiota in relation to pets and siblings.

METHODS

The study population comprised a small sub-sample of 24 healthy, full term infants from the Canadian Healthy Infant Longitudinal Development (CHILD) birth cohort. Mothers reported on household pets and siblings. Fecal samples were collected at 4 months of age, and microbiota composition was characterized by high-throughput signature gene sequencing.

RESULTS

Microbiota richness and diversity tended to be increased in infants living with pets, whereas these measures were decreased in infants with older siblings. Infants living with pets exhibited under-representation of Bifidobacteriaceae and over-representation of Peptostreptococcaceae; infants with older siblings exhibited under-representation of Peptostreptococcaceae.

CONCLUSIONS

This study provides new evidence that exposure to pets and siblings may influence the early development of the gut microbiota, with potential implications for allergic disease. These two traditionally protective "hygiene hypothesis" factors appear to differentially impact gut microbiota composition and diversity, calling into question the clinical significance of these measures. Further research is required to confirm and expand these findings.

Exposure to cats: update on risks for sensitization and allergic diseases

Cats are the pets most commonly implicated in the etiology of asthma and allergic disease. However, systematic reviews have concluded that there is a lack of evidence to support the idea that cat exposure in early life increases the risk of allergic disease. Indeed, it appears most likely that cat exposure is protective against allergic diseases. Recent large prospective studies have shown that living with a cat during childhood, especially during the first year of a child's life, could be protective. However, any advice given to the parents should also incorporate how new acquisition of cats can affect other family members, especially those who are already sensitized. Research is urgently needed to determine whether the suggested impact of acquisition of cats in adult life is modified by the person's childhood pet ownership, to help parents who seek advice on whether or not to get a cat.

Respiratory health in home and leisure pursuits

Many home-based and leisure activities can generate hazardous respirable exposures. Routine domestic activities and a variety of hobbies, avocations, and leisure pursuits have been associated with a spectrum of respiratory tract disorders. Indoor environments present a special risk for high-intensity exposures and adverse health effects. There are important knowledge gaps regarding the prevalence of specific health hazards within and across communities, exposure-response effects, population and individual susceptibilities, best management strategies, the adverse health effects of mixed exposures, and long-term clinical outcomes following exposures. The home environment presents special health risks that should be part of the health assessment.

Epidemiology of asthma in the United States

Incidence and prevalence rates of asthma can vary greatly according to population and location. The National Heart and Blood Institute of the National Institutes of Health defines asthma as a common chronic disorder of the airways that involves a complex interaction of airflow obstruction, bronchial hyperresponsiveness, and an underlying inflammation. This article uses the most common definitions and diagnostic methods for asthma. In 2009 there were 2.1 million asthma-related emergency department (ED) visits. ED visits lend an opportunity for providers to identify and intervene in the care of patients whose asthma is poorly controlled.

Pets at birth do not increase allergic disease in at-risk children

BACKGROUND

The literature is contradictory concerning pet exposure and risk of allergic disease in childhood especially among those with a family history of allergy.

OBJECTIVE

To investigate the relationship between cat and dog exposure at birth and allergic outcomes over the first 12 years in a birth cohort selected for familial allergy.

METHODS

A prospective birth cohort of 620 infants with a family history of allergic diseases was recruited. Data on pet keeping, family demographics and cord blood samples were collected at birth. Information on childhood wheeze, eczema and hay fever was collected 18 times in the first 2 years, at 7 years and at 12 years. Skin prick tests were conducted at 2, 7 and 12 years, and in parents. Regression analyses were used to investigate the relevant associations while adjusting for potential confounders.

RESULTS

Exposure to cats or dogs at birth showed a moderate reduction in risk of wheeze (aOR = 0.76; 95% CI 0.53, 1.09) and hay fever (aOR = 0.71; 0.49, 1.02) after 7 years of age. Protective effects were stronger in children of non-sensitized fathers (aOR wheeze 0.55; 0.31, 0.98; aOR hay fever 0.33; 0.15, 0.77 on exposure to cats alone, or cats or dogs at birth). Pet keeping was not related to cord blood IgE or sensitization from 2 to 12 years.

CONCLUSIONS AND CLINICAL RELEVANCE

Pets at birth either decreased or had no effect on allergic disease up to age 12. We found no evidence that exposure to cats or dogs at birth increases the risk of allergic disease in high-risk children.

Childhood asthma: diagnosis and treatment

Many children suffer from recurrent coughing, wheezing and chest tightness. In preschool children one third of all children have these symptoms before the age of six, but only 40% of these wheezing preschoolers will continue to have asthma. In older school-aged children the majority of the children have asthma. Quality of life is affected by asthma control. Sleep disruption and exercised induced airflow limitation have a negative impact on participation in sports and social activities, and may influence family life. The goal of asthma therapy is to achieve asthma control, but only a limited number of patients are able to reach total control. This may be due to an incorrect diagnosis, co-morbidities or poor inhalation technique, but in the majority of cases non-adherence is the main reason for therapy failures. However, partnership with the parents and the child is important in order to set individually chosen goals of therapy and may be of help to improve control. Non-pharmacological measures aim at avoiding tobacco smoke, and when a child is sensitised, to avoid allergens. In pharmacological management international guidelines such as the GINA guideline and the British Guideline on the Management of Asthma are leading.

Environmental Toxicology: Children at Risk

Children today live in a world that is vastly different from a few generations ago. While industrialization has maximized (for many) children’s opportunities to survive, develop and enjoy high levels of health, education, recreation, and fulfillment, it has also added significant challenges to their development.

Gene-environment interactions in the development of asthma and atopy

Asthma is a complex multifactorial disorder involving a variety of different mechanisms. Little has changed in asthma treatment over the past five decades. There is evidence for a strong genetic component of asthma, but genetic studies have produced heterogeneous results with little replication, with most of the heritability remaining unexplained. The rapid increase in asthma prevalence over a short time period suggests that environmental exposures play an important role, but there is a considerable heterogeneity in the results describing the effect of different environmental exposures. There are many reasons for the lack of replication in genetic association studies and those of environmental exposures. These include the failure to consider that asthma may arise as a consequence of environmental factors, modulating the risk in genetically susceptible individuals via gene-environment interactions. In addition, many studies rely on oversimplified phenotypes often derived through aggregation of several heterogeneous conditions (e.g., 'physician-diagnosed asthma').

Does pet ownership in infancy lead to asthma or allergy at school age? Pooled analysis of individual participant data from 11 European birth cohorts

OBJECTIVE

To examine the associations between pet keeping in early childhood and asthma and allergies in children aged 6-10 years.

DESIGN

Pooled analysis of individual participant data of 11 prospective European birth cohorts that recruited a total of over 22,000 children in the 1990s. EXPOSURE DEFINITION: Ownership of only cats, dogs, birds, rodents, or cats/dogs combined during the first 2 years of life. OUTCOME DEFINITION: Current asthma (primary outcome), allergic asthma, allergic rhinitis and allergic sensitization during 6-10 years of age.

DATA SYNTHESIS

Three-step approach: (i) Common definition of outcome and exposure variables across cohorts; (ii) calculation of adjusted effect estimates for each cohort; (iii) pooling of effect estimates by using random effects meta-analysis models.

RESULTS

We found no association between furry and feathered pet keeping early in life and asthma in school age. For example, the odds ratio for asthma comparing cat ownership with "no pets" (10 studies, 11489 participants) was 1.00 (95% confidence interval 0.78 to 1.28) (I(2) = 9%; p = 0.36). The odds ratio for asthma comparing dog ownership with "no pets" (9 studies, 11433 participants) was 0.77 (0.58 to 1.03) (I(2) = 0%, p = 0.89). Owning both cat(s) and dog(s) compared to "no pets" resulted in an odds ratio of 1.04 (0.59 to 1.84) (I(2) = 33%, p = 0.18). Similarly, for allergic asthma and for allergic rhinitis we did not find associations regarding any type of pet ownership early in life. However, we found some evidence for an association between ownership of furry pets during the first 2 years of life and reduced likelihood of becoming sensitized to aero-allergens.

CONCLUSIONS

Pet ownership in early life did not appear to either increase or reduce the risk of asthma or allergic rhinitis symptoms in children aged 6-10. Advice from health care practitioners to avoid or to specifically acquire pets for primary prevention of asthma or allergic rhinitis in children should not be given.

Effect of cat and daycare exposures on the risk of asthma in children with atopic dermatitis

Atopic dermatitis (AD) in young children is often followed by the development of asthma (atopic march). The role of environmental exposures is unclear in this high-risk population. We aimed to determine the predictive relationship between indoor allergen exposures, particularly pets, rodents, and cockroaches, to the development of asthma in a prospective pediatric cohort. Children with AD and a family history of allergy were followed prospectively with questionnaire ascertainment of environmental exposure to cats, dogs, cockroaches, rats, and mice. Asthma was diagnosed by study physicians based on caregiver reports of symptoms continually assessed over the course of the study period. Fifty-five of the 299 children developed asthma by the end of the study. Cat exposure had a strong and independent effect to reduce the risk of developing asthma across all analyses (odds ratio [OR], 0.16; 95% confidence interval [CI], 0.05-0.53). Dog, mouse, rat, and cockroach exposures did not significantly influence the development of asthma. Daycare exposure had the largest risk reduction for the development of asthma (OR, 0.08; 95% CI, 0.03-0.19). Maternal asthma (OR, 2.93; 95% CI, 1.29-6.67), baseline body mass index (OR, 1.23; 95% CI, 1.08-1.42), and specific immunoglobulin E to house-dust mix at 3 years were each independent risk factors for the development of asthma. In children with AD, cat and daycare exposure may reduce the risk of developing early childhood asthma.

The heterogeneity of asthma phenotypes in children and young adults

Objective. Genetic heterogeneity and risk factor distribution was analyzed in two previously proposed asthma phenotypes. Method. A sample of 412 subjects was investigated at 7-8, 12-13, and 21-22 years of age with questionnaires, skin prick tests, and genetic analysis of IL-4 receptor (IL4R) single-nucleotide polymorphisms. The sample was subdivided in one group with no asthma, and two groups with asthma separated by age of onset of symptoms, namely, early onset asthma (EOA) and late onset asthma (LOA). Risk factors and IL4R markers were analyzed in respect to asthma phenotypes. Results. EOA and LOA groups were both associated with atopy and a maternal history of asthma. Female gender was more common in LOA, whereas childhood eczema, frequent colds in infancy, and a paternal history of asthma were more common in EOA. The AA genotype of rs2057768 and the GG genotype of rs1805010 were more common in LOA, whereas the GG genotype of rs2107356 was less common in EOA. Conclusion. Our data suggest that early and late onset asthma may be of different endotypes and genotypes.

Determinants of asthma after severe respiratory syncytial virus bronchiolitis

BACKGROUND

The development of asthma after respiratory syncytial virus (RSV) bronchiolitis has been demonstrated in case-control studies, although the determinants of post-RSV asthma remain undefined.

OBJECTIVES

We sought to evaluate the potential determinants of physician-diagnosed asthma after severe RSV bronchiolitis during infancy.

METHODS

We enrolled 206 children during an initial episode of severe RSV bronchiolitis at 12 months of age or less in a prospective cohort study and followed these children for up to 6 years. In a subset of 81 children, we analyzed CCL5 (RANTES) mRNA expression in upper airway epithelial cells.

RESULTS

Forty-eight percent of children had physician-diagnosed asthma before the seventh birthday. Independent determinants significantly associated with increased risk for physician-diagnosed asthma by the seventh birthday included maternal asthma (odds ratio [OR], 5.2; 95% CI, 1.7-15.9; P = .004), exposure to high levels of dog allergen (OR, 3.2; 95% CI, 1.3-7.7; P = .012), aeroallergen sensitivity at age 3 years (OR, 10.7; 95% CI, 2.1-55.0; P = .005), recurrent wheezing during the first 3 years of life (OR, 7.3; 95% CI, 1.2-43.3; P = .028), and CCL5 expression in nasal epithelia during acute RSV infection (OR, 3.8; 95% CI, 1.2-2.4; P < .001). White children (OR, 0.19; 95% CI, 0.04-0.93; P = .041) and children attending day care (OR, 0.18; 95% CI, 0.04-0.84; P = .029) had a decreased risk of physician-diagnosed asthma.

CONCLUSIONS

Approximately 50% of children who experience severe RSV bronchiolitis have a subsequent asthma diagnosis. The presence of increased CCL5 levels in nasal epithelia at the time of bronchiolitis or the development of allergic sensitization by age 3 years are associated with increased likelihood of subsequent asthma.

The indoor air and asthma: the role of cat allergens

PURPOSE OF REVIEW

The objective is to discuss recent progress in our understanding of the role of the indoor environment in asthma, focusing on the special role of cat allergens.

RECENT FINDINGS

Sensitization to Fel d 1 is the dominant event in inhalant responses to cat; however, there are also IgE responses to the lipocalin (Fel d 4), to cat albumin (Fel d 2), and to the oligosaccharide galactose-alpha-1,3-galactose (alpha-gal) on cat IgA (Fel d 5w) and other molecules. The dose response and routes of sensitization for these allergens are now thought to be diverse. It is important to remember that exposure outside a house with a cat is sufficient to cause sensitization. Furthermore, the only solid evidence about a role in asthma relates to Fel d 1. Recently, it has been shown that tolerance associated with early exposure to cats can persist to age 18 and that IgE to alpha-gal (on cat IgA) is not related to asthma. In addition, a recent study of anti-IgE reinforces the evidence that IgE antibodies to indoor allergens make a major contribution to asthma severity.

SUMMARY

Exposure to Fel d 1 in a home with a cat is far higher than the levels necessary to induce an allergic (IgE antibody) response. In keeping with that, children may develop tolerance, which can be long-lived. In addition, there is increasing evidence that IgE antibodies to an inhalant allergen, such as Fel d 1, dust mite, or cockroach, are causally related to lung inflammation and asthma.

Lifetime dog and cat exposure and dog- and cat-specific sensitization at age 18 years

BACKGROUND

Prior research about whether keeping a dog or cat at home causes allergies to that pet has been limited to outcomes in early childhood.

OBJECTIVE

Evaluate the association between lifetime dog and cat exposure and allergic sensitization to the specific animal at 18 years of age.

METHODS

Participants enrolled in the Detroit Childhood Allergy Study birth cohort during 1987-1989 were contacted at the age 18 years. Sensitization to dog or cat was defined as animal-specific IgE ≥ 0.35 kU/L. Annual interview data from childhood and follow-up interviews at age 18 years were used to determine lifetime indoor dog and cat exposure (indoor was defined when the animal spent >50% of their time inside the house). Exposure was considered in various ways: first year, age groups and cumulative lifetime. Analyses were conducted separately for dogs and cats.

RESULTS

Among males, those with an indoor dog during the first year of life had half the risk [relative risk (RR)=0.50, 95% confidence interval (CI) 0.27, 0.92] of being sensitized to dogs at age 18 compared with those who did not have an indoor dog in the first year. This was also true for males and females born via c-section (RR=0.33, 95% CI 0.07, 0.97). Overall, teens with an indoor cat in the first year of life had a decreased risk (RR=0.52, 95% CI 0.31, 0.90) of being sensitized to cats. Neither cumulative exposure nor exposure at any other particular age was associated with either outcome.

CONCLUSIONS AND CLINICAL RELEVANCE

The first year of life is the critical period during childhood when indoor exposure to dogs or cats influences sensitization to these animals.

Association of house dust mite-specific IgE with asthma control, medications and household pets

Background

Evidence is conflicting regarding the effectiveness of creating a low-allergen environment or reducing allergen exposure to control asthma exacerbations.

Objective

This study determined the association of house dust mite (HDM)-specific IgE levels with asthma symptom control, selected medications, family history of allergic disease, and exposure to second-hand smoke and household pets.

Methods

Serum samples from 102 doctor-diagnosed allergic asthma patients and 100 non-atopic controls were subjected to enzyme-linked immunosorbent assay using the HDM species Dermatophagoides pteronyssinus (Dp), Dermatophagoides farinae (Df), and Blomia tropicalis (Bt) allergens. Point-biserial correlation coefficient, Pearson R correlation, and logistic regression analyses were used to determine association of HDM-specific IgE levels with the abovementioned variables.

Results

Of the 102 cases, 38.24%, 47.06%, and 33.33% were sensitized to Bt, Df, and Dp, respectively. Sensitized patients showed greater probability [Bt (OR = 1.21), Df (OR = 1.14), and Dp (OR = 1.35)] to manifest symptoms than those who were not. Obtained p-values [Bt (p = 0.73), Df (p = 0.83), and Dp (p = 0.59)], however, proved that HDM-specific IgE levels had no significant contribution in predicting or explaining occurrence of asthma symptoms. Bt- and Df-specific IgEs showed moderately weak but significant relationship with bambuterol HCl and expectorant, respectively. Patients currently on said medications registered higher HDM-specific IgE levels than those who were not. No significant correlation between IgE levels and family history of allergic disease or with exposure to second-hand smoke was seen. Dp-specific IgE levels of patients exposed to household pets were significantly lower compared to those without exposure.

Conclusion

This study proves that sensitization to Bt, Df, and Dp allergens is not significantly associated with asthma symptoms and control. Although cases were shown to be sensitized to HDMs, their current medications were at least effective in controlling their asthma symptoms.

Allergens and their role in the allergic immune response

Allergens are recognized as the proteins that induce immunoglobulin E (IgE) responses in humans. The proteins come from a range of sources and, not surprisingly, have many different biological functions. However, the delivery of allergens to the nose is exclusively on particles, which carry a range of molecules in addition to the protein allergens. These molecules include pathogen-associated molecular patterns (PAMPs) that can alter the response. Although the response to allergens is characterized by IgE antibodies, it also includes other isotypes (IgG, IgA, and IgG4), as well as T cells. The challenge is to identify the characteristics of these exposures that favor the production of this form of response. The primary features of the exposure appear to be the delivery in particles, such as pollen grains or mite feces, containing both proteins and PAMPs, but with overall low dose. Within this model, there is a simple direct relationship between the dose of exposure to mite or grass pollen and the prevalence of IgE responses. By contrast, the highest levels of exposure to cat allergen are associated with a lower prevalence of IgE responses. Although the detailed mechanisms for this phenomenon are not clear, it appears that enhanced production of interleukin-10 in response to specific Fel d 1 peptides could influence the response. However, it is striking that the animal sources that are most clearly associated with decreased responses at high allergen dose are derived from animals from which humans evolved more recently (∼65 million years ago). Although the nose is still recognized as the primary route for sensitization to inhalant allergens, there is increasing evidence that the skin is also an important site for the generation of IgE antibody responses. By contrast, it is now evident that delivery of foreign proteins by the oral route or sublingually will favor the generation of tolerance.

Asthma phenotypes in adults and clinical implications

It is becoming increasingly recognized that asthma is a heterogeneous disease, whether based on clinical factors, including the patient's age at diagnosis, symptom spectrum and treatment response, triggering factors, or the level and type of inflammation. Attempts to analyze the importance of these characteristics to the clinical presentation of asthma have led to the appreciation of numerous separate and overlapping asthma phenotypes. However, these approaches are 'biased' and based on the clinician/scientist's own experience. Recently, unbiased approaches have also been attempted using both molecular and statistical tools. Early results from these approaches have supported and expanded on the clinician's concepts. However, until specific biologic markers are identified for any of these proposed phenotypes, the definitive nature of any phenotype will remain speculative.

Levels of endotoxin in 390 Swedish homes: determinants and the risk for respiratory symptoms in children

Endotoxins are microbiological agents which ubiquitously exist in an indoor environment, and are believed to be causal agents for a number of diseases. This study investigated the indoor levels and determinants of endotoxins and their impact on asthma and allergy diseases among Swedish pre-school children. House dust samples from 390 homes of 198 case children with asthma and allergy and 202 healthy control children were collected in the Dampness Building and Health (DBH) study. House dust endotoxin levels in the child's bedroom and living rooms ranged from 479-188,000 EU/g dust and from 138-942,000 EU/g dust, respectively. Pet-keeping and agricultural activities were significantly associated with the higher endotoxin concentration levels in indoor dust. Endotoxins in theindoor environment did not associate to asthma and allergy diseases in the children. However, we found an association between endotoxins and the presence of disease symptoms in the sub-group of families without indoor pets.

[Relationships between indoor allergens, sensitization, and allergic asthma and rhinitis symptoms]

INTRODUCTION

There is a strong and consistent association between immediate hypersensitivity, asthma and exposure to allergens. However, the role that the inhaled allergen plays and the timing of events related to sensitization are still controversial.

BACKGROUND

Information obtained by studies of the follow-up of cohorts underlines the fact that there is no continuum between specific IgE responses and the development of childhood asthma. Allergic rhinitis and asthma result from a complex and multifactorial interaction between genetic factors, exposure to allergens, and many biological or chemical co-factors. However, when the child is exposed to an allergen, sensitization to the allergen is a risk factor for childhood asthma and severity of the disease.

CONCLUSIONS AND VIEWPOINTS

Despite numerous epidemiological studies, the association and links between atopy, allergens, environment, sensitization and allergic rhinitis and/or asthma remain difficult to evaluate and poorly understood. Complementary studies are also necessary for the standardization of therapeutic strategies.

Indoor pet exposure and the outcomes of total IgE and sensitization at age 18 years

BACKGROUND

Early-life exposure to household pets has been shown to be protective against allergic sensitization in childhood.

OBJECTIVE

We sought to evaluate the association between early-life pet exposure and allergic sensitization at age 18 years.

METHODS

Teenagers who had been enrolled in the Detroit Childhood Allergy Study birth cohort in 1987-1989 were contacted at age 18 years. Serum total and allergen-specific IgE levels to 7 common allergens (dust mite, cat, dog, ragweed, Timothy grass, Alternaria species, and peanut; atopy was defined as any specific IgE level > or =0.35 kU/L) were measured at age 18 years. Annual interview data from childhood were used to determine indoor dog and cat (> or =50% of their time in the home) exposure during early life. Exposure was considered in various ways: first year, cumulative lifetime, and age groups, as well as multiple pets.

RESULTS

Dog or cat exposure in the first year of life was not associated with atopy (relative risk, 0.97; 95% CI, 0.83-1.12). Those living with pets in the first year and atopic at 18 years had lower total IgE levels. Neither cumulative exposure nor exposure at a particular age was strongly and consistently associated with either outcome. Although not statistically significant, there was a pattern of decreased odds of sensitization among those with 2 or more pets versus no pets in the first year of life.

CONCLUSIONS

Early-life pet exposure can be associated with lower total IgE levels among atopic subjects but is not strongly associated with decreased likelihood of sensitization to common allergens at age 18 years.