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

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.

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.

• 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.

• 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.