Background: Smoking exposure is known as a health hazard; however, a longitudinal analysis of the impact of smoking exposure in family on the allergic reactions related to childhood atopic diseases has not been well addressed.

Methods: Children completed a 3-year follow-up period from a birth cohort were enrolled. Smoking exposure history was recorded and urine cotinine levels were measured at 1, and 6 months, and 1, 2, and 3 years of age.  Specific IgE levels against food and mite allergens were measured at age 6 months, and 1, 2 and 3 years. Their relevance to the family smoking exposure and subsequent development of atopic diseases were also analyzed.

Results: A total of 198 infants were enrolled in this study. The prevalence of passive smoking exposure in children was as high as 45%. Urine cotinine levels were significantly higher in children with smoking exposure history (P < 0.001). Compared to children without smoking exposure, food-specific IgE levels and the prevalence of eczema were significantly higher in children with smoking exposure at age 6 months (P <0.05). By contrast, urine cotinine levels were observed to be significantly higher in children with IgE sensitization (> 100 kU/L, P < 0.05) at age 3, which was also significantly associated with a higher prevalence of allergic rhinitis, and asthma development (P < 0.01).

Conclusion: Family smoking exposure is strongly associated with food sensitization in infancy and IgE production in later childhood, which may potentially increase susceptibility to develop infantile eczema and childhood airway allergies subsequently.