Microbiome, dysbiosis, and atopic dermatitis

The loss of diversity in a normal skin microbiome known as dysbiosis is observed in most patients with atopic dermatitis (AD). In particular, staphylococcal colonization is correlated with the severity of AD, and it is thought to be a possible trigger for AD. However, the questions of whether staphylococcal colonization precedes the development of AD, and whether the colonization of commensal microbiota is protective against the occurrence of eczema have been controversial. In addition to the genetic skin barrier dysfunctions, virulence factors generated by Staphylococcus species may enhance the impairment of barrier functions, and they may induce allergic inflammation via innate and adaptive immunity. This chapter summarizes the current knowledge on the pathogenic link between the skin microbiome and AD.