Child characteristics, household, and home environmental factors associated with eczema: a cross-sectional study.

UNLABELLED: Childhood eczema is influenced by genetic susceptibility, socioeconomic conditions, and indoor environmental exposures and practices, yet few studies have examined these domains simultaneously. This study investigates factors associated with doctor-diagnosed eczema among school-aged children, considering child and home characteristics. A cross-sectional study was conducted, inviting parents/legal guardians of children (5-11 years) attending 20 primary schools in Porto, Portugal. Of the 2717 invited participants, 1263 (46.5%) completed questionnaires on child and household characteristics, respiratory and allergic outcomes, and housing characteristics and practices; 1227 were included. Mixed-effects logistic regression models with a random intercept for school were used to estimate adjusted odds ratios (aORs) and 95% confidence intervals (CIs), accounting for clustering and multiple imputation for missing data. After adjusting for covariates, increasing age (aOR = 1.03, 95% CI 1.00-1.06), postnatal secondhand smoke exposure (aOR = 1.48, 95% CI 1.26-1.73), family history of eczema (aOR = 3.53, 95% CI 3.00-4.15), higher family income (> 3000€ vs. ≤ 1000€; aOR = 1.40, 95% CI 1.11-1.77), residence within 300 m of traffic zones (aOR = 1.32 95% CI 1.11-1.48), and all-purpose cleaner use (aOR = 1.16, 95% CI 1.01-1.33) were independently associated with higher odds of eczema. Higher maternal education (aOR = 0.68, 95% CI 0.37-0.86), living in detached houses (aOR = 0.67, 95% CI 0.52-0.87), and fur blanket use (aOR = 0.85, 95% CI 0.74-0.97) were associated with lower odds of eczema. Interaction analyses further indicated that the association between household dampness and eczema varied according to residence type and winter ventilation frequency. CONCLUSION: Childhood eczema was associated with a range of familial, socioeconomic, residential, and household environmental factors. Longitudinal studies are warranted to clarify temporal relationships and the mechanisms underlying these associations. WHAT IS KNOWN: • Childhood eczema is associated with genetic and environmental factors, including dampness and secondhand smoke exposure. • Few studies have comprehensively examined multiple factors associated with childhood eczema. WHAT IS NEW: • This study identified independent associations of socioeconomic, housing, and indoor environmental factors with eczema after comprehensive adjustment. • Housing characteristics and ventilation modified dampness-related eczema associations, suggesting context-dependent environmental influences.