Objectives Environmental exposure at home, such as dampness, has been shown to have adverse effects on respiratory health. However, few studies explored the association between home dampness and genetic polymorphisms on childhood asthma. The aim of the study is to evaluate the effects of home dampness and tumour necrosis factor-α gene (TNF-α) on asthma in Taiwanese children.

Methods The authors investigated 3810 schoolchildren in Taiwan Children Health Study from 14 communities. Children's exposure and disease status were measured from a parental questionnaire. Multiple logistic regression models were fitted to estimate the effects of home dampness exposure and TNF-α genotypes on the prevalence of asthma and wheeze.

Results Mildewy odour at home was significantly associated with increased prevalence of lifetime wheeze (OR=1.36, 95% CI 1.05 to 1.77, p for trend=0.04). The effects of water stamp on the wall at home were associated with lifetime asthma and lifetime wheeze. Children with water stamp on the wall at home and TNF-308 A allele had increased risks on lifetime asthma, active asthma and lifetime wheeze. TNF-α showed significant interactive effects with mildewy odour on lifetime asthma (p for interaction=0.01), and with water stamp on the wall at home on lifetime wheeze (p for interaction=0.04). Under stratification by TNF-308 genotypes, we found that the frequency of water stamp on the wall was associated with increased risks of all asthma subcategories and lifetime wheeze among TNF-308 GA or AA genotypes (p for trend<0.05).

Conclusions Home dampness is a risk factor for asthma and wheeze among children, especially for those with the TNF-308 A allele.