Early-life mercury exposure and allergic diseases in childhood: systematic review and meta-analysis

Mercury is a persistent environmental contaminant that can cross the placenta and accumulate in fetal tissues. While its neurotoxic effects are well established, its potential association with allergic diseases in children remains unclear. Understanding how early-life mercury exposure relates to the burden of allergic conditions is important for child health and environmental risk assessment.

We conducted a systematic review and meta-analysis of observational studies reporting allergic outcomes in children with measured mercury exposure. PubMed and Embase were searched from inception to October 2025. Studies were eligible if they assessed prenatal or postnatal mercury exposure and reported at least one allergic outcome. Random-effects meta-analysis was used to estimate pooled prevalence of allergic outcomes reported in studies.

Sixteen studies were included. The pooled prevalence among mercury-exposed children was 6.2% (95% CI, 1.8-18.8%) for asthma, 18.6% (95% CI, 9.0-34.5%) for atopic dermatitis, 14.4% (95% CI, 3.2-46.2%) for eczema, 15.8% (95% CI, 3.3-50.9%) for allergic rhinitis, and 22.3% (95% CI, 13.2-35.2%) for wheezing. Heterogeneity was high (I² > 90%). Studies from East Asia, which reported higher mercury exposure and fish intake, showed greater allergic disease proportions than European cohorts.

Allergic diseases were frequent among populations in which mercury exposure was assessed, with regional and exposure-timing differences contributing to heterogeneity. The findings highlight the need for harmonised, prospective studies to clarify the role of mercury exposure in childhood allergic disease development.