Skin and gut microbiota dysbiosis in autoimmune and inflammatory skin diseases

The human body is inhabited by complex communities of microorganisms. Changes in the composition and function of the skin and gut microbiota are linked to various skin diseases. The microbiota is an important modulator of the immune system and thus maintains homeostasis. Conversely, the immune system can also change the composition of the microorganism community. Thus, it is still unknown whether certain skin diseases are caused by primary changes in the local and/or remote microbiota, or whether dysbiosis is only a secondary consequence of the dermatoses themselves. Expanding knowledge of skin and gut microbiota dysbiosis in skin diseases may possibly lead to better understanding of their pathophysiologies and to the discovery of new molecular markers for their earlier diagnosis and targeted treatment; for example, using specific microbes to replace missing ones. This narrative review provides an overview of current knowledge about skin and gut microbiota dysbiosis in psoriasis, atopic dermatitis, hidradenitis suppurativa, seborrheic dermatitis, acne vulgaris, rosacea, and lichen sclerosus.