Infant Skin Microbiome: How Early Life Exposures Shape Health

AN INSIGHTFUL study has shown that the infant skin microbiome during the first year of life is shaped by a complex interplay of body site, age, genetics, environment, and early-life exposures, with clear associations with atopic dermatitis (AD). Understanding the Infant Skin Microbiome While the gut microbiome has been widely studied in early life, the skin microbiome remains comparatively underexplored, particularly in relation to AD. In this study, researchers analysed skin bacterial communities in infants from the Enquiring About Tolerance (EAT) birth cohort to better understand how early exposures influence microbial composition and skin barrier function. The study included 148 infants assessed at 3 months and 1 year of age. Bacterial swabs were taken from two skin sites, the elbow crease and volar forearm, and analysed using 16S rRNA gene sequencing. Clinical assessments for AD were conducted at enrolment, and again at 1 and 3 years, alongside measurements of transepidermal water loss (TEWL), filaggrin mutation status, and detailed parental questionnaires. Key Microbial and Environmental Associations Microbiome diversity varied significantly by body site, with higher Shannon diversity observed on the forearm compared with the elbow crease. Across both time points and sites, Staphylococcus, Acinetobacter, and Streptococcus were the most abundant bacterial genera. Community composition was most strongly associated with body site and age (both p≤0.001). However, several early-life factors also showed significant associations, including ethnicity, filaggrin mutation status, urban versus rural residence, having older siblings, and bath product use at 3 months. In contrast, no significant associations were found with pet ownership, systemic antibiotic use, or bathing frequency. Links to Skin Barrier Function and Atopic Dermatitis Importantly, the skin microbiome was associated with elevated TEWL at both 3 months and 1 year, indicating a link with impaired skin barrier function. Microbial composition was also significantly associated with concurrent AD at both time points. Notably, Streptococcus parasanguinis was less abundant in non-lesional skin of infants with AD at 3 months, suggesting early microbial signatures linked to disease. Clinical Implications The findings suggest that modifiable environmental and hygiene-related factors, alongside genetic predisposition, influence early skin microbial development and may contribute to AD risk. Understanding these relationships could inform future prevention strategies targeting the skin microbiome in infancy. Reference Broderick C et al. Associations between early-life exposures and the infant skin microbiome. Br J Dermatol. 2026; doi:10.1093/bjd/ljaf524.