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Tobacco exposure before and after birth increases childhood allergies

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A large new study evaluated the risk if prenatal and postnatal tobaccos smoke exposure for asthma, rhinitis (inflammation of nasal membranes), and eczema (skin rash). The study was published online on August 18 in the journal Pediatrics by Swedish researchers.

The study group comprised 4,089 children who were followed from birth to age 16 years. Information on parental smoking habits, lifestyle factors, and symptoms of allergic disease was collected via repeated parental questionnaires. The investigators used generalized estimating equations to determine the overall and age-specific associations between second hand smoke exposure and allergic disease at ages 1 to 16 years.

The investigators found that exposure to second hand smoke in utero (before birth) was associated with an overall increased risk of developing asthma up to age 16 years (1.45-fold increased risk) but not for rhinitis or eczema. After additional adjustment of the data for parental smoking throughout childhood, excess overall risks for asthma remained statistically significant. In addition a dose-dependent relationship with second hand smoke was found. Exposure to secondhand smoke during infancy was associated with an overall increased risk of asthma (1.23-fold increased risk), rhinitis (1.18-fold increased risk), and eczema (1.26-fold increased risk) up to 16 years of age. When age-specific relationships were evaluated, the elevated risks related to secondhand smoke exposure in utero or during infancy were mainly confined to early childhood for asthma and rhinitis; however, the excess risk of eczema appeared greatest at older ages.

The authors concluded that early secondhand smoke exposure, in utero or during infancy, influences the development of allergic disease up to adolescence. Increased risks for asthma and rhinitis were seen primarily in early childhood; in contrast, those for eczema occurred at later ages.

The authors are affiliated with: Department of Clinical Science and Education, Stockholm South General Hospital, Karolinska Institutet, Stockholm, Sweden; Centre for Occupational and Environmental Medicine, Stockholm County Council, Stockholm, Sweden; Department of Women’s and Children’s Health, Uppsala University Hospital, Uppsala, Sweden; and Sachs’ Children’s Hospital, Södersjukhuset, Stockholm, Sweden.