Smoking and the development of allergic sensitization to aeroallergens in adults: a prospective population-based study. The Copenhagen Allergy Study

Background: Several cross-sectional population-based studies have reported a negative association between smoking and allergic sensitization to aeroallergens. In a prospective study, we investigated the association between smoking and the development (incidence) of allergic sensitization as reflected by skin prick test (SPT) positivity and specific IgE positivity. Methods: Participants in a population-based study of 15-69-year-olds in 1990 were invited to a follow-up in 1998. Thus, SPT positivity and specific IgE positivity to common aeroallergens were assessed in 734 subjects (participation rate: 69.0%) on two occasions 8 years apart. The effect of smoking on the development of allergic sensitization was adjusted for potential confounders such as age, sex, family history of hay fever, educational level, and total IgE. Results: During the follow-up period, 58 and 33 subjects developed SPT positivity and specific IgE positivity, respectively. The risk of developing SPT positivity (adjusted odds ratio: 0.45, 95% CI 0.21-0.98) and specific IgE positivity (adjusted odds ratio: 0.62, 95% CI 0.26-1.49) was lower among sustained smokers than never-smokers. Conclusions: In this adult population, sustained smoking was negatively associated with the development of allergic sensitization to aeroallergens during an 8-year follow-up. This negative association, if real, might be due to an immunosuppressive effect of smoking.