Indoor Allergen Sensitization Research Articles

A Novel Link between Early Life Allergen Exposure and Neuroimmune Development in Children

As COVID-19 unprecedented situation significantly increased the time families spend indoors, the awareness of unhealthy living conditions negatively impacting immune system and early neurodevelopment of children is of crucial importance. We retrospectively reviewed unrelated cases of the children with confirmed multiple indoor allergen sensitization due to prolonged exposure to unhealthy indoor environment with infestation and water damage, who, in addition to multiple health problems related to allergy and asthma, also developed neuroimmune complications and growth delay. Documented early in life atypical neurologic and behavioral changes were common in all cases. Clinical analysis did not establish other causative reason aside from prenatal and early life exposure to unhealthy living conditions. Alternaria Alternara and Penicillium/Aspergillus molds were found in all homes and sensitization was confirmed in all cases. Significant similarities in the symptoms recorded in all three families led us to a hypothesis that, likely, a significant level of the immune response to external immunogenic pathological stimulus such as mold spore protein, mycotoxin protein, dust mite protein, decay-related volatile particles (VOC) skewed a balance of the neuroimmune interactions, and further affected neuronal network establishment. As all children exhibited significant spectrum of the systemic inflammatory conditions early in life, coupled with inability to follow normal neurodevelopment, we hypothesize that an overwhelming activation of the aggressive immune mechanisms by the epigenetic factors led to glia activation, cytokine storm and break of tolerance. We hypothesize that developing immune system exhibited aggressive responses due to environmental danger signals, subsequently TH-1 or TH-2 switch enables multiple clinical syndromes development with atypical presentation due to the described novel mechanism. An increased due to the COVID-19 lock-down may increase an amount of exposure of vulnerable people to indoor biological particles and volatile organic compounds present in unhealthy buildings. It is of crucial importance to identify and remediate indoor exposure factors that can decrease immune protection, especially against infectious pathogens such as novel coronavirus.

Material Hardship and Indoor Allergen Exposure among Low-Income, Urban, Minority Children with Persistent Asthma.

Traditional measures of socioeconomic status (SES) are associated with asthma morbidity, but their specific contributions are unclear. Increased exposure to indoor allergens among low SES children is an important consideration. Material hardship, a concept describing poor access to basic goods and services, may explain the relationship between low SES and indoor allergen exposure, and thereby, the increased risk of asthma morbidity. We sought to (i) describe the specific hardships experienced by low-Income, urban, minority children with asthma and indoor allergen sensitization and (ii) determine if material hardship is associated with indoor allergen exposure in this population. We conducted a cross-sectional analysis of children undergoing the baseline assessment for a clinical trial of home environmental modification. Participants were scored in five domains of material hardship. Domain scores were assigned based on caregiver responses to a questionnaire and were summed to generate a total material hardship score. Linear regression was used to examine the relationship between material hardship scores and bedroom floor concentrations of five common indoor allergens. Participants experienced high levels of material hardship in each of the five domains, with 33% not having access to a car, 35% not being able to pay utility bills, and 28% not being able to pay rent in the past year. Each one-point increase in material hardship was associated with an increase in cockroach allergen of 16.2% (95% CI 9.4%, 24.6%) and an increase in mouse allergen of 9.4% (95% CI 1.0%, 18.5%). After adjusting for traditional measures of SES, including household income, health insurance type, caregiver education, and caregiver employment status, the association between material hardship and cockroach allergen, but not mouse allergen, remained. These data suggest that a significant proportion of families of low-income, minority children with asthma may experience material hardship, and that they may be at greater risk of cockroach allergen exposure than their peers with similar income, but without material hardship.

Sensitization to indoor allergens in children with bronchial asthma

BACKGROUND: Children with asthma have a high prevalence of environmental allergies. Sensitization to various allergens, especially to indoor allergens is crucial for effective measures for asthma management. Indian data on allergic sensitization in children is scarce, necessitating the need of the study. METHODS: A Cross-sectional study was conducted to determine the indoor allergen sensitization in 100 asthmatic children aged 5 to 15 yrs. They underwent skin prick test for indoor allergen house dust mite cockroach, cat, dog dander, house fly, candida, aspergillus, and mosquito. RESULTS: In the study sensitization to house dust mite was 93%. 39% were sensitized to Candida 36% to cockroach,23% housefly and 22%to dog dander and Aspergillus and 13% to mosquito and cat dander. Allergen sensitivity rate for atleast one allergen was 94% which was significant. Mean No. of allergens for which sensitization was seen is 2.57±1.77. Comorbidities were present in 35% of cases.7% had urticarial and allergic conjunctivitis each. CONCLUSION: Asthmatic children showed high sensitization to indoor allergen and the most common allergen found was house dust mite

Profiles and characteristics of bronchial responsiveness in general 7-year-old children.

Although bronchial responsiveness (BR) is usually categorized as normal or hyperresponsive to aid the diagnosis of asthma, it exists on a continuous spectrum, not in a dichotomous manner. We aimed to evaluate the distribution profile of BR in a generalpopulation of 7-year-olds. In 2015, 7-year-old Korean children from a nationwide birth cohort study visited regional study hospitals for skin prick test, standard spirometry, and bronchial provocation to establish reference values for the general population. Their BR degrees were categorized into five ordered groups: hyperresponsive BRs were classified into group 1 (provocative concentration (PC) of methacholine causing a 20% fall in forced expiratory volume in 1 second [FEV1], PC20 of <4 mg/mL) and group 2 (PC20 of ≥4 mg/mL and <16 mg/mL), and nonresponsive BRs were categorized into group 3 (final FEV1 percentage fall after inhaling 16 mg/mL of methacholine [FEV1%fall] of >15% and ≤20%), group 4 (FEV1%fall of >10% and ≤15%), and group 5 (FEV1%fall of ≤10%). In total, 559 subjects finished all tests reliably. Groups 1 and 2 comprised 10.0% and 15.7% of the total population, respectively. Groups 3, 4, and 5 comprised 14.7%, 18.4%, and 41.1%, respectively. As the group number increased, the proportion of those with recent wheezing and those with indoor allergen sensitization decreased (P for trend = 0.001 and P for trend < 0.001, respectively), and the baseline FEV1/FVC increased (P for trend < 0.001) CONCLUSION: BR of the 7-year-olds in the general population, while showing a wide distribution across phenotypes, is associated with allergic symptoms, negatively correlated with baseline lung function and positively correlated with indoor allergen sensitization.

Indoor Allergen Sensitization Correlates with Asthma in Chicago Public Hospital Patients

Indoor Allergen Sensitization Correlates with Asthma in Chicago Public Hospital Patients

Is there an association between indoor allergens and the severity of atopic dermatitis?

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease with frequent hypersensitivity to allergens. However, the role of exposure to indoor allergens on AD severity is unclear. Children aged 0-17 years with active AD from central Chile were recruited; disease severity was evaluated with SCORAD and POEM scores. A home environment survey was applied to parents. Bedroom dust samples were collected for all subjects and analyzed by multiplex assay to quantify dust mite (Der p1, Der f1), dog (Can f1), cat (Fel d1), and alternaria alternata (Alt a1) allergens. Twenty-five children aged 3.9 ± 3.8 years were included. Fifty-two percent were female. Mean SCORAD was 29 ± 14 (range 11-61), and mean POEM was 10.7 ± 6.2. No direct association was found between tobacco exposure, pet ownership, aerosol use, visible dust, or home carpets/rugs with SCORAD (all P > 0.05). Dust samples from all homes had Can f1 and Fel d1 allergens, regardless of pet ownership. Homes that had indoor dogs or cats had significantly higher amounts of these allergens (P < 0.001). Forty percent of homes had dust mite allergens, and none had alternaria alternata. Children with AD living in homes with elevated dust mite and animal dander allergen concentrations had higher SCORAD than those from homes with low allergen concentrations (40 ± 13 vs. 26 ± 13, P = 0.025). High concentrations of indoor allergens may influence AD severity in children. Further studies assessing indoor allergens and allergen sensitization are warranted to fully evaluate the role of indoor allergens on AD.

Evaluation of skin prick test to screen dust mite sensitization in chronic respiratory diseases in Southern Vietnam.

BackgroundIn the view of the epidemic growth of sensitization to indoor allergens in Southern Vietnam, there is a requirement to screen large population.ObjectiveTo evaluate skin prick tests (SPTs) as predictors of positive specific IgE (sIgE) to dust allergens, among patients with chronic respiratory diseases (CRDs).MethodsThe sensitization to Blomia tropicalis (Blo t), Dermatophagoides pteronissinus (Der p), and Blattella germanica allergens (Bla g) were evaluated among 610 CRD, both SPT (≥4 mm) and sIgE by immuno-CAP (≥0.7 kUA/L).ResultsBased on sIgE, 45%, 32%, and 33% of patients with CRD were sensitized to Blo t, Der p, and Bla g, respectively, compared to 19%, 18%, and 13% by SPT. The association between SPT and sIgE was statistically significant, though the Kappa factor was fair (i.e., 0.39 to 0.23). While the specificity of SPT to detect sensitization (compared to sIgE) was >90% among the whole population, the sensitivity was only 34%, 41%, and 24% for Bo t, Der p, and Bla g, suggesting that SPT was not enough sensitive to screen the indoor allergen sensitization. Though, among the <10 pack-year (PY) smokers, the sensitivity was 43% for Blo t, 52% for Der p, and 61% for Blo t and/or Der p, compared to 27%, 30%, and 35% among the ≥10 PY smokers. The sensitivity/specificity was not associated with the diagnosis of asthma compared to chronic obstructive pulmonary disease.ConclusionIn the present circumstance, SPT to dust mites allergens can be used to detect a sensitization among CRD population in Southern Vietnam.

House dust mites induce proliferation of severe asthmatic smooth muscle cells via an epithelium-dependent pathway.

Asthma is a frequent airway disease, and asthma control determinants have been associated with indoor allergen sensitization. The most frequent allergens are house dust mites (HDM), which act in vivo on the bronchial epithelial layer. Severe asthma has also been associated with bronchial remodeling and more specifically with increased mass of bronchial smooth muscle (BSM). However, the relationship between HDM stimulation of the bronchial epithelial layer and BSM remodeling is unknown. To evaluate whether epithelial stimulation with HDM induces BSM cell proliferation in subjects with severe asthma. A total of 22 subjects with severe asthma and 27 subjects with no asthma were recruited. We have developed an in vitro culture model combining an epithelium layer in air-liquid interface (ALI) interacting with BSM. We assessed BSM proliferation using BrdU incorporation. We explored the role of epithelium-derived mediators using reverse-transcriptase polymerase chain reaction (RT-PCR) and ELISA in vitro and in vivo. Finally, leukotrienes receptor expression was assessed in vitro by flow cytometry and RT-PCR and ex vivo by laser microdissection and RT-PCR. We found that epithelial stimulation by HDM selectively increased the proliferation of asthmatic BSM cells and not that of nonasthmatic cells. The mechanism involved epithelial protease-activated receptor-2-dependent production of leukotrienes C4 associated with an overexpression of leukotrienes receptor CysLTR1 by asthmatic BSM cells in vitro and ex vivo. This work demonstrates the selective role of HDM on BSM remodeling in patients with severe asthma and points out different therapeutic targets at epithelial and smooth muscle levels.

Childhood asthma and indoor allergen exposure and sensitization in Buffalo, New York

This nested case-control study examined the association between prevalent asthma and indoor allergen sensitization and/or exposure among children (aged 5-17 years) in Buffalo, New York. The study included a self-administered questionnaire, clinical interviews, skin allergen sensitivity tests and home dust sampling for house dust mites, cat, dog, cockroach and mouse allergens. After adjusting for multiple confounders, asthma cases had higher odds of being sensitized to Der p dust mites (odds ratio [OR]=1.94, 95% confidence interval (CI): 1.13-3.35), cat (OR=1.96, 95% CI: 1.13-3.39), or dog allergens (OR=1.89, 95% CI: 1.10-3.22) than the controls. A significantly positive association between asthma status presence of cat allergen in the child's mattress (ORs: 2.61, 95% CI: 1.09-6.28) was also found. Children with both sensitization and environmental exposure to cat allergens had higher odds of asthma (OR=7.08, 95% CI: 2.12-23.62) than those who were only sensitized to cat allergen (OR=2.31, 95% CI: 1.01-5.32) or had only home exposures (OR=1.47, 95% CI: 0.47-4.65). The association between allergen sensitization and asthma was more consistent than for home exposures. The findings help to confirm the role of allergen sensitization and home exposure in regard to asthma, and suggest that both, individually and jointly, are associated with asthma.

Indoor allergen sensitization and the risk of asthma and eczema in children in Pittsburgh

Several studies have shown that sensitization to cockroach and mouse allergens is correlated with presence and severity of asthma, especially among children living in inner cities. This study evaluated the prevalence of positive skin testing to indoor allergens in the Pittsburgh area and the association with asthma and eczema. A retrospective analysis was performed of 540 children from the Pittsburgh area who underwent skin testing to indoor allergens. Presence of asthma and eczema were determined by parent and/or physician report. Asthma and eczema are not significantly more frequent among children who had positive skin testing to cockroaches or mice. However, asthma was more common among children who had positive skin testing to dogs (odds ratio [OR], 1.4; 95% CI, 1.23-1.65), cats (OR, 1.4; 95% CI, 1.21-1.58), and dust mites (OR, 1.2; 95% CI, 1.03-1.37). Eczema was more common in children who had positive skin testing to cats (OR, 1.5; 95% CI, 1.14-2.02). Both asthma (OR, 1.4; 95% CI, 1.18-1.58) and eczema (OR, 1.4; 95% CI, 1.07-1.92) were more prevalent among children with any positive skin test. We did not find that sensitization to cockroaches or mice was correlated with the diagnosis or asthma or eczema in the Pittsburgh area. However, sensitization to any allergen, and to cats and/or dogs specifically, was associated with diagnosis of both asthma and eczema. Our result suggests that allergic sensitization is associated with these diseases, but the implicated allergens may vary.

Correlation between Demographic Characteristics and Indoor Allergen Sensitization among a Farming Community (FC), a Local Community (LC), and an Urban Region (UR) in South Korea

Correlation between Demographic Characteristics and Indoor Allergen Sensitization among a Farming Community (FC), a Local Community (LC), and an Urban Region (UR) in South Korea

Indoor allergen exposure, sensitization, and development of asthma in a high-risk birth cohort

Contradictory findings have been observed for the association of house dust mite (HDM), cat, and dog allergen exposure with sensitization and asthma. We sought to determine the relationship between exposures to these allergens, at various points during early childhood, and specific sensitization and asthma at age 7 in a high-risk birth cohort. As part of a multi-faceted Canadian intervention program for the primary prevention of asthma in high-risk infants, children were assessed by pediatric allergists at age 7 for asthma and underwent allergy skin prick testing. House dust samples were analyzed for HDM, cat, and dog allergen levels at several time points during years 1 and 7 of life. Multiple logistic regression analyses were carried out for the combined cohort and separately for the control and intervention groups. Exposure to a higher level of HDM allergen in year 1 or year 7 was associated with a higher risk of year 7 sensitization to HDM but not asthma. Exposure to higher levels of cat allergen in year 1 or year 7 did not affect the risk of year 7 sensitization to cat or asthma. Dog ownership, or exposure to higher levels of dog allergen in year 1 or year 7, did not affect the risk of year 7 sensitization to dog; however, year 7 dog allergen exposure (intervention group only) or ownership was associated with increased year 7 asthma risk. Our findings suggest that in high-risk children, there are allergen-specific associations of exposure with sensitization and with asthma; early life-elevated HDM exposure was associated with risk of sensitization but not asthma while the opposite was true for dog exposure.

Factors Affecting Bronchial Hyperreactivity in Asthmatic Children

Bronchial hyperresponsiveness (BHR), the exaggerated airway narrowing in response to nonspesific stimuli, is a common characteristic of asthma. One hundred thirty-five children who were diagnosed asthma in the outpatient clinic of Gazi University Hospital, Pediatric Allergy and Asthma Department between January 2007 and January 2008 were retrospectively analysed from the asthma database of the division. BHR was not found to be different according to sex. Younger the age of the patient, more severe was BHR (p = 0.096, r = 0.164). Younger the age at onset of the symptoms, the more severe was the BHR (p < 0.001, r = 0.307). Patients who had an asthmatic first degree relative and who were exposed to passive smoking at home, had more severe BHR (p = 0.006 and p = 0.032, respectively). There were more hospitalizations among the asthmatic children with moderate-severe BHR (p = 0.027) however no correlation was found between chronic asthma severity and the degree of BHR). In this study we found that age, age at onset of symptoms, having a parent with asthma, exposure to tobacco smoke and baseline lung function are related to BHR measured at referral. Serum levels of Ig E or skin prick test positivity were not found to have any effect on BHR severity. Considering BHR severity, we could not reveal any relation between atopic and nonatopic children. However among atopic subjects, the ones with indoor allergen sensitization had more severe BHR.

Lack of association between indoor allergen sensitization and asthma morbidity in inner-city adults

Sensitivity and exposure to indoor allergens is associated with increased asthma morbidity in inner-city children. However, it is unknown whether sensitization is associated with worse asthma in adults. To evaluate the relationship between sensitization and asthma morbidity in urban adults. We prospectively studied 245 adults with persistent asthma recruited from an inner-city clinic. Sensitization to indoor allergens was evaluated by specific IgE antibodies measured at enrollment. Data on asthma control, asthma-related emergency department visits, hospitalizations, and oral steroid use were collected at baseline and at 1-month and 3-month follow-up contacts. Univariate, stratified, and multiple regression analyses were used to compare asthma morbidity in sensitized and nonsensitized patients after controlling for self-reported exposure and other potential confounders. The study cohort consisted predominantly of low income, minority patients with high rates of resource utilization. The prevalences of sensitization to cockroach, dust mite, cat, mold, and mouse were 60%, 43%, 41%, 21%, and 14%. On univariate analyses, patients sensitized to each allergen did not have worse asthma control or higher resource utilization compared with nonsensitized individuals. Stratified and multivariate analyses also showed no association between sensitization and several measures of asthma morbidity even after controlling for self-reported exposure to indoor allergens and other potential confounders. Sensitization to indoor allergens does not appear to be associated with increased asthma morbidity in inner-city adults. These findings suggest that efforts to improve asthma control among urban populations should focus on other modifiable risk factors for morbidity.

Evaluation of the relationship between cockroach sensitivity and house-dust-mite sensitivity in Turkish asthmatic patients

Exposure to cockroach has been identified as an important source of indoor allergens in patients with asthma and allergic rhinitis. We evaluated the relationship between cockroach sensitivity and other allergens in patients with asthma. A total of 114 patients, defined asthma according to GINA, were enrolled in this study. A questionnaire including age, sex, duration of asthma, history of cockroach presence at home, and total IgE, blood eosinophil count, pulmonary function tests, standard skin prick test additional cockroach and shrimp allergen were performed. There were 84 (73.7%) female and 30 (26.3%) male patients with a mean age of 38.1+10.1 years. The average duration of asthma was 7.7+7.2 years. Sixty five (57%) patients were determined atopic and 49 (43%) nonatopic. Pollen allergen was the most common allergen in 59 (51.8%) patients with asthma, and second common allergen was mite allergen in 43 (37.7%) patients. Cockroach sensitivity were detected in 23 (20.2%) of 114 all asthmatics and 23 (35%) of atopic asthmatics. High rates of house-dust-mite allergy (73.9%) was determined in patients with cockroach sensitivity (P<0.05), while we found no relationship with other allergens. There was no difference for cockroach sensitivity between rural and urban population. Cockroach sensitivity was more common in mild bronchial asthmatics and a female predominance was observed. In addition, there was no association between shrimp and cockroach sensitivity. As a result, a high rate of cockroach sensitivity alone or with mite sensitivity was seen in patients with bronchial asthma in Turkish population. Because of cross-reactivity between mites and cockroach, cockroach sensitivity should be investigated in patients with house-dust-mite allergy. In addition, a high rate of cockroach sensitivity, in terms of IgE sensitization, may be important for the development of new sensitizations.

The role of indoor allergen sensitization and exposure in causing morbidity in women with asthma.

Longitudinal evidence that indoor allergen exposure causes morbidity in sensitized individuals with asthma is scarce. We evaluated the association of allergen sensitization and home exposure to short- and long-term morbidity in 140 women with asthma and to asthma prevalence in 458 women from metropolitan Boston. Cockroach (Blattella germanica), dust mite (Dermatophagoides farinae), and cat (Felis domesticus) allergens in home dust samples, and specific immunoglobulin E antibodies were measured at outset, and doctor-diagnosed asthma and markers of asthma morbidity were ascertained by questionnaire during a 4-year follow-up. Cat- and cockroach-sensitive (immunoglobulin E immunocap [Cap] class > or = 1) women with asthma reported greater morbidity in the past year at the start, and during follow-up, if high levels of the relevant allergen were found. Women with asthma sensitized to cat allergen and with concentrations at 8 microg/g or greater were more likely to have used steroid (adjusted odds ratio [95% confidence interval] 2.7 [1.2-6.2]) and wheezed without a cold (odds ratio 6.8 [3.3- 14.0]) during follow-up. Those sensitized and exposed to cockroach (Bla g 1 or 2 > or = 2 U/g) were at least three times more likely to have used steroid and to have attended a hospital emergency room; the size of the effect upon steroid use was maintained, but the precision was reduced and the 95% confidence interval included one (p = 0.07), with adjustment for race and poverty. We conclude that cockroach and cat allergens may contribute to asthma morbidity in sensitized women.

Effect of current exposure to Der p 1 on asthma symptoms, airway inflammation, and bronchial hyperresponsiveness in mite-allergic asthmatics

The existence of a dose-response relationship between indoor allergen exposure and sensitization has been widely described, but the effect of allergen exposure on asthma activity (symptoms, bronchial hyperresponsiveness [BHR], and inflammation) is not clear. Our aim was to determine the existence of an association among current exposure to mite allergens and symptoms, BHR, and airway inflammation assessed in blood and sputum from asthmatic patients sensitized to Dermatophagoides pteronyssinus. We selected 31 mild and recently diagnosed (12-24 months) asthma patients sensitized to D. pteronyssinus. Allergenic exposure (Der p 1, Der 2) was assessed by a commercial assay based on monoclonal antibodies (mAb), carried out on the dust samples collected from patients' beds in a standardized way. Patients completed an asthma symptom questionnaire and underwent skin tests, methacholine bronchial challenge, and sputum induction. Sputum cell profile was analyzed and eosinophil cationic protein (ECP), tryptase, albumin, and interleukin(IL)-5 levels were quantified in sputum supernatant. Total eosinophil numbers and ECP levels were measured in blood samples. Most patients were exposed to Der p 1 levels under 2 microg/g of dust. Der p 1 exposure was higher among the subjects with positive sputum tryptase detection (P = 0.020). Der p 1 levels showed a trend toward correlation with asthma symptoms (P = 0.066, r = 0.36) and correlated with sputum tryptase levels (P = 0.032, r = 0.42). No relationship between BHR, eosinophilic inflammation, and allergenic exposure was found. Our results suggest that asthma symptoms and lung mast-cell activation are at least partially dependent on current allergen exposure. The lack of correlation between mite exposure, eosinophilic inflammation, and BHR supports the role of other factors that enhance the immunologic response initiated by allergen, increasing the activity of asthma.

Comparative degree and type of sensitization to common indoor and outdoor allergens in subjects with allergic rhinitis and/or asthma

The determinants of variability in the clinical expression of atopy are still to be documented. The goals of this study were to determine, in subjects with a clinical diagnosis of symptomatic asthma or rhinitis, what is the possible contribution of different types of indoor and outdoor allergens to the development of their disease, by looking at the prevalence and degree of sensitization to these allergens according to age and gender. We analysed allergy skin prick tests to common airborne indoor and outdoor allergens in 3371 consecutive patients, grouped according to diagnosis of allergic asthma, rhinitis, or both. For each of these three groups, we calculated the prevalence of sensitization to indoor/outdoor allergens, the atopic index (AI), the number of positive responses to allergy skin prick test and the mean wheal diameter (MWD) of these responses. The prevalence of atopy and the values of AI and MWD peaked in subjects aged 16 to 25 years, declining afterwards; in subjects > or = 18 years old, atopic indices were slightly higher in men than in women. In atopic subjects, the prevalence of sensitization was, in decreasing order, housedust (84.2%), cat hair-epithelium (76.5%), dog hair-dander (63.0%), house dust mite (54.2%), grasses (51.9%), trees (47.2%) and ragweed pollens (44.9%) and finally, moulds (25.4%). Among subjects sensitized only to outdoor allergens (n = 195). 73.8% had a rhinitis, 11.8% had asthma and 14.4% had both diagnoses; for those sensitized only to indoor allergens (n = 710), these values were respectively 48.6, 24.5 and 26.9%, and for those sensitized to both indoor and outdoor allergens (n = 1793), the comparable values were 55.5, 14.6 and 29.9%. These data show that in our population of subjects with respiratory allergic symptoms, indoor allergen sensitization is strongly associated with asthma, while exclusive sensitization to pollens is associated primarily with rhinitis. Sensitization was more prevalent for indoor allergens than for outdoor allergens in all groups determined according to diagnosis or age. Indices of atopy were higher in men in the group > or = 18 years old. Prevalence and degree of sensitization were shown to peak in young adults, regardless of the allergen, and to diminish with age. This study stresses the role of indoor allergens in the development of asthma and shows the variability of allergic manifestations according to the type of sensitization.