International variation in prevalence of rhinitis and its relationship with sensitisation to perennial and seasonal allergens.

The relative importance of atopy in the aetiology of rhinitis is largely unknown. The present study investigated the geographical variations in rhinitis in relation to atopy. The cross-sectional study involved 54,178 children (aged 8-12 yrs) from 30 study centres in 22 countries worldwide. Symptoms of rhinoconjunctivitis and rhinitis without conjunctivitis in the last 12 months were reported in parental questionnaires and children were skin-prick tested. The prevalence of rhinoconjunctivitis and rhinitis without conjunctivitis varied widely (1.5-24.5% and 1.4-45.2%, respectively). For rhinoconjunctivitis, the population attributable fraction (PAF) varied 0-71% for a positive skin-prick test to one or more seasonal allergens and 0-41% for perennial allergens. The PAF for sensitisation to seasonal and perennial allergens was higher in affluent countries (36 and 25%, respectively) than nonaffluent countries (1.3 and 12.6%, respectively). For rhinitis without conjunctivitis, the PAF for perennial allergens was 8 and 4% for affluent and nonaffluent countries, respectively. No significant PAF was found for seasonal allergens. Overall, atopy explained only a limited proportion of rhinitis symptoms, suggesting that the importance of other environmental factors has been under emphasised, particularly in less affluent countries. Atopy seems to be only marginally relevant for rhinitis without conjunctivitis, which seems mainly to reflect nonatopic rhinitis.