Addressing microbial inequity in urban children: the case for dirty play

Source abstract

Urbanisation has widened the ‘nature gap’ (the systemic disparity in access to natural environments), limiting children’s opportunities for contact with biodiverse environments and the microbes (e.g. bacteria, fungi, viruses) they host. This paper introduces the concept of Dirty Play – unstructured, tactile engagement with soils, mud and other natural materials – as a strategy to address both developmental and microbial inequities in cities. Synthesising evidence from microbiome science, environmental psychology, and early childhood education, we argue that dirty play supports immune regulation, sensory and cognitive development, and emotional wellbeing. Contact with microbially rich substrates can enhance skin and gut microbiota diversity, promoting immune balance and stress resilience, while simultaneously nurturing curiosity, creativity and nature connectedness. Yet cultural biophobia, urban design norms, and unequal access to green space constrain such experiences, particularly for children in low-income and marginalised communities. In this conceptual paper, we outline design and policy recommendations for microbially inclusive urban playscapes, including the integration of biodiverse substrates, vegetation, and child-led co-design processes. By reframing ‘dirt’ as a developmental and ecological medium rather than a contaminant, dirty play offers a framework for health equity and sensory rewilding in the Anthropocene – restoring human-microbial interactions, imagination and belonging to urban childhoods.