An Altered Skin and Gut Microbiota Are Involved in the Modulation of Itch in Atopic Dermatitis

Abstract

Skin and gut microbiota play an important role in the pathogenesis of atopic dermatitis (AD). An alteration of the microbiota diversity modulates the development and course of AD, e.g., decreased microbiome diversity correlates with disease severity, particularly in lesional skin of AD. Itch is a hallmark of AD with unsatisfying treatment until now. Recent evidence suggests a possible role of microbiota in altering itch in AD through gut-skin-brain interactions. The microbial metabolites, proinflammatory cytokines, and impaired immune response lead to a modulation of histamine-independent itch, disruption of epidermal barrier, and central sensitization of itch mechanisms. The positive impact of probiotics in alleviating itch in AD supports this hypothesis, which may lead to novel strategies for managing itchy skin in AD patients. This review summarizes the emerging findings on the correlation between an altered microbiota and gut-skin-brain axis in AD, especially in modulating itchy skin.

Keywords: atopic dermatitis; gut; itch; microbiota; skin.

Figure 1

Proposed mechanism of a microbiota dysbiosis modulates itch in atopic dermatitis. The leaky gut condition due to gut dysbiosis enables microbiota metabolites and proinflammatory cytokines to circulate and reach the skin, e.g., tryptophan, LPS, and others. In the skin, decreased microbial diversity and S. aureus colonization lead to disruption of skin barrier function and the production of pruritoceptors, such as IL-4, IL-13, TSLP, IL-31, and so on, which trigger an itch sensation in AD.