Background: A family history of allergy, reflecting genetic risk factors, increases the risk of developing allergic diseases, but environmental factors, especially those present in early life, also contribute to the actual development of allergic phenomena.
Objective: To identify differences in lifestyle between allergic and non-allergic parents, which may influence the prevalence of environmental risk factors in their homes.
Methods: Data were collected in a Dutch birth cohort study by postal questionnaire about 2 months before and 3 months after the birth of the child.
Results: Of the 3147 infants in the study 1910 (61%) had two non-allergic parents, of 315 infants (10%) only the mother was allergic, of 787 infants (25%) only the father was allergic and 135 (4%) infants had two allergic parents. If both parents were allergic, 53% reported that allergy was taken into consideration when they furnished their home and significantly more of their homes were free of cats and free of cigarette smoke; adjusted odds ratio's for two allergic parents vs. two non-allergic parents were 0.30 (confidence interval (CI) 0.17-0.50) for the presence of cats and 0.46 (CI 0.27-0.75) for smoking in the home. Parental allergy was also associated with having a smooth floor in the baby's bedroom and with postponement of the introduction of fruits and vegetables until the age of 26 weeks. The presence of dogs at home, the prevalence of mothers' smoking during pregnancy and the decision to breast feed were unrelated to parental allergy.
Conclusion: We conclude that studies on the relationship between allergy in parents and allergy in their offspring should always consider the home environment as a potential confounder. For allergy prevention our results imply that among allergic parents there is awareness and willingness to take measures that reduce exposure to indoor allergens.