The Microbiome in Atopic Dermatitis

As an interface with the environment, the skin is a complex ecosystem, colonized by many microorganisms that coexist in an established balance. The cutaneous microbiome inhibits colonization with pathogens such as S. aureus and is a crucial component for function of the epidermal barrier. Moreover, crosstalk between commensals and the immune system is now recognized, as microorganisms can modulate innate, as well as adaptive, immune responses. Host-commensal interactions also have an impact on the developing immune system in infants and subsequently the occurrence of diseases such as asthma and atopic dermatitis. Later in life, the cutaneous microbiome contributes to the development and course of skin disease. Accordingly, in patients with atopic dermatitis, a decrease in microbiome diversity correlates with disease severity and increased colonization with pathogenic bacteria such as S. aureus. Early clinical studies suggest that topical application of commensal organisms (e.g., S. hominis or R. mucosa) reduces atopic dermatitis severity and support an important role for commensals in decreasing S. aureus colonization in patients with atopic dermatitis. Advancing knowledge of the cutaneous microbiome and its function in modulating the course of skin disorders such as atopic dermatitis may result in novel therapeutic strategies.