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Background: Alteration of environmental factors and air pollution affects the trend of allergic diseases especially in cities such as Tehran. This study aimed to determine the prevalence of allergic rhinitis, conjunctivitis, atopic dermatitis and asthma among adults in the capital city of Iran. Methods: This cross-sectional study was performed between 2013 and 2016 in Tehran, Iran. The participants were adults between 18 and 45 yr of age. A specific questionnaire including demographic data and clinical symptoms was filled out by a trained interviewer. The diagnosis of allergic diseases was performed based on standard questionnaires and criteria. Results: The prevalence of allergic rhinitis, conjunctivitis, asthma and atopic dermatitis were 28.3%, 15.9%, 7.6% and 3.9%, respectively. Allergic rhinitis and conjunctivitis together were reported in 12.3% of the participants. Among patients with asthma, 47.4% had AR. Additionally, 25.7% of atopic dermatitis subjects were reported to have asthma. The subjects with at least one of these allergic diseases were 36.3%. Women showed a higher prevalence of allergic symptoms than men. There was a significant relationship between allergic symptoms and family history of atopic diseases. Conclusion: The most common allergic disease was allergic rhinitis. Regarding the comorbidity of asthma and allergic rhinitis, paying more attention to controlling these allergic diseases is deemed necessary.

Allergic sensitization to inhalant allergens could be considered as a predictor in allergic diseases. The objective of this study was to assess IgE-mediated sensitization to inhalant allergens in allergic and non-allergic adults as well as the evaluation of its association with allergic diseases. This cross-sectional study was conducted from 2013 to 2016 in 604 allergic and 102 non-allergic adults selected from blood donor volunteers in Tehran, Iran. After taking informed consent, a standard questionnaire was filled to determine asthma, allergic rhinitis and/or conjunctivitis and atopic dermatitis in participants. Specific IgE assay to common inhalant allergens was performed for all subjects. Logistic regression analysis was used to evaluate the impact of IgE sensitization on allergic diseases. A total of 371(61.4%) allergic subjects and 41(40.2%) non-allergic patients were males. The weeds (especially saltwort) and grasses (particularly meadow fescue and ryegrass) were identified as the most common inhalant allergens. The prevalence of IgE sensitization to trees, weeds, and grasses was higher in subjects with allergic rhino-conjunctivitis and trees sensitization was a significant factor in them [OR=2.32, 95% CI (1.58-3.41)]. IgE sensitization to any inhalant allergens could be a predictor for allergic rhinitis, conjunctivitis and rhino-conjunctivitis in adults [OR=2.20, 95% CI (1.54-3.15], [OR=1.81, 95% CI (1.28-2.54)] and [OR=2.55, 95% CI (1.72-3.78)], respectively. With an increase in the sum of specific IgE concentrations, the prevalence of allergic conjunctivitis and rhino-conjunctivitis also increased. Our results showed the association between positive specific IgE and its concentration with some allergic diseases which could help physicians to prevent such diseases by recognizing and treating them, particularly in individuals with a positive family history of allergic diseases.