Short-chain fatty acids (SCFAs) are the products of plant polysaccharides fermented by the gut commensal microbiota, including acetate, propionate, and butyrate.There is evidence that gut commensal microbes affect the mucosal immune system via expansion of regulatory T cells (Tregs) in the colon. This is mediated via short-chain fatty acids, bacterial metabolites generated during fiber fermentation, which include butyrate, propionate, and acetate.The mechanisms responsible for the communication between the comensal bacteria of the skin and the immune system may be compared to what happens in the intestine. Gut commensal microbes influence the mucosal immune system through the increase of Tregs, and this is mediated by the SCFAs. Because skin commensal bacteria also contain SCFAs producing strains,animmunomodulatory/anti-inflammatory mechanism like that in the gut also exists in the skin. Among SCFAs, butyrate suppresses immune responses by inhibiting cytokines and inflammatory cell production and promotes Tregs proliferation, the main cells involved in many physiologic functions of the skin, such as hair follicle regulation, stem cell differentiation, and wound healing. Inflammatory skin diseases are characterized by a disrupted cutaneous immune response and skin microbiome (SM)dysbiosis. Through the production of butyrate, commensal skin microbes may counteract exaggerated inflammatory responses by exerting a down-regulatory function and maintaining a homeostatic state under physiologic conditions. Whereby, topical butyrate administration may become a useful therapeutic application with a "curative" potential on inflammatory skin diseases.

Atopic Dermatitis (AD) is a chronic inflammatory skin disease that usually begins in early infancy, but also affects a significant number of adults. It has been demonstrated that low fecal levels of SCFAs have been linked to AD development in infants, and have been reported higher levels of gut butyrate-producing bacteria in healthy infants than in those with severe AD. In AD murine model, the oral intake of a probiotics mixture plus sodium butyrate determined an increase of Th1 and Tregs differentiation, and of the population of butyrate-producing bacteria, thereby alleviating AD symptoms. Furthermore, butyrate in addition to the anti-inflammatory effects, also exerts Staphylococcus aureus bactericidal activity, confirming the immunomodulatory effects of butyrate in mitigating AD.

The chronic exposure to UVB radiation alters the cutaneous and systemic immune systems, causing several skin cell signaling alterations resulting in erythema, sunburn, inflammation, and carcinogenesis. It has been shown that butyric acid alone topical application remarkably ameliorated the UVB-induced inflammation on mice skin. Butyric acid noticeably decreased the ulceration of the skin and the epidermal thickness from UVB exposure. Therefore, butyrate can be effective not only for overt skin diseases, but as an ingredient in cosmetic products, to prevent skin alterations.

According to current science, the best strategy for treating and preventing skin diseases should be to maintain the homeostasis of skin commensal microbiome. This strategy is considered safe, free from toxic and side-effects, industrially scalable, and easily formulated into cosmetic skin care products. Topical application of butyrate, the probiotic metabolite, to the skin showed attenuate skin disorders and maintain skin microbiome homeostasis. However, how to eliminate the unpleasant sensory factors of butyric acid will be one of the important keys for the development of butyric acid skin preparations.

  1. Serena Coppola, Carmen Avagliano, Antonia Sacchi, Sonia Laneri, Antonio Calignano, LuanaVoto, Anna Luzzetti and Roberto BerniCanani.Potential Clinical Applications of the Postbiotic Butyrate in Human Skin Diseases.Molecules 2022, 27, 1849. https://doi.org/10.3390/molecules27061849
  2. AgathaSchwarz, AnikaBruhs, and ThomasSchwarz. The Short-Chain Fatty Acid Sodium Butyrate Functions as a Regulator of the Skin Immune System. Journal of Investigative Dermatology Volume 137, Issue 4, April 2017, Pages 855-864.