B@seball - Environmental bacteria link green schoolyards to better child well-being and fewer allergy symptoms

Understanding how biodiverse environments influence children's health is critical for reducing allergies and other immune disorders. We investigated the impact of green schoolyards and associated bacteria on well-being and allergies in over 520 children across 37 Belgian schools. Using environmental and skin microbiome sequencing, alongside children's participation in environmental sampling, natural elements scoring, and questionnaires, we found that children from schools with a green schoolyard had better well-being and fewer allergy symptoms, predominantly in urban and low socioeconomic settings. Specific schoolyard bacteria, including Bacillus, Microbacteriaceae, and Pseudomonas, were prevalent on children's skin and negatively associated with allergy symptoms. Their schoolyard abundance correlated with schoolyard biodiversity and landscape type. Mechanistically, these bacteria showed adherence to skin cells - important for retention and host interaction - and immunostimulatory activity in human monocytes. These findings reveal how green school environments and associated microbial exposure may support children's health and guide microbiome-informed greening interventions.