Effect of pre- and postnatal tobacco smoke exposure on specific sensitization to food and inhalant allergens during the first 3 years of life

Background: The study aimed to assess the effect of pre- and postnatal toba cco smoke exposure on specific sensitization to food allergens and inhalant allergens during the first 3 years of life. Methods: A total of 342 children of a prospective and observational birth c ohort study on atopy (MAS) were included on the basis of a complete follow- up of specific IgE measurements at the ages of 1, 2, and 3 years with avail able questionnaire information about-the parental smoking habit at birth, 1 8 months, and 3 years of age. Study children were grouped into four exposur e categories representing in utero and postnatal environmental tobacco smok e (ETS) exposure, and according to the number of cigarettes smoked by the p arents. The effect on the development of allergic sensitization to food, ou tdoor, and indoor allergens by 3 years of age was determined by multiple lo gistic regression analyses. Results: At the age of 3, children who were pre- and postnatally exposed to tobacco smoke had a significantly higher risk of sensitization to food all ergens (odds ratio: 2.3, 95% C.I.: 1.1-4.6) than unexposed children. Childr en who were only postnatally exposed by a smoking mother also had a 2.2 tim es higher risk (95% C.I.: 0.9-5.9) of sensitization than unexposed children . These two categories (pre- and/or postnatal exposure) contribute to the s ignificant overall effect of the tobacco smoke exposure (P less than or equ al to 0.02). No significant association between tobacco smoke exposure and specific sensitization to inhalant allergens was observed. The determining risk factors for this type of sensitization were atopic family history and mite- and cat-allergen exposure levels. Conclusions: During the first 3 years of life, both prenatal and postnatal tobacco smoke exposure has an adjuvant effect on allergic sensitization whi ch seems to be restricted to allergens to which children are mainly exposed , in combination with the peak of the ETS exposure around the first birthda y.