In utero and childhood exposure to parental tobacco smoke, and allergies in schoolchildren

Among early-life environmental factors, parental smoking (ETS) has been associated with adverse respiratory outcomes in children. The aim of the study was to evaluate whether parental smoking might lead to asthma and allergies taking into account family history of asthma, personal atopy, breast feeding as confounders and owing pets and day-care during the first 6 months of life as modifiers. About 9000 children of fourth and fifth grade were selected in six cities of France. About 7798 answered an epidemiological questionnaire, underwent a medical examination including skin prick test positivity to common allergens, skin examination for eczema, and run test to assess exercise-induced asthma (EIA). Prevalence of allergies was, respectively, 25.2% for eczema, 12.9% for rhinitis, 9.9% for asthma and 25% for atopy. About 8.3% had an EIA. About 21.6% of children were exposed to maternal tobacco smoking during pregnancy. Maternal smoking, in utero and later, was significantly related to lifetime wheezing (odds ratio (OR): 1.24[1.10–1.56]) and asthma (OR: 1.22[1.04–1.66]). There was no association between atopy, rhinitis, eczema and parental smoking, respectively. ETS remains a risk factor of wheezing in childhood. Counselling parents of children to quit smoking still remains a public health policy.