Gut microbes and skin disease, gut-brain-skin axis: A review

Skin disease, especially eczema, dermatitis and acne, may damage appearance of people, and cause physical discomfort or mental disorders. The prevalence rate is increasing sharply and globally that has been affected all populations in the world. The diseases have various, complex pathogeny and high recurrence rate. Studies demonstrate that skin and mental state are closely related, emerging of skin diseases always accompanied with prevalence of mental disorders obviously. As early as 1930s, the dermatologist John H. Stokes and Donald M. Pillsbury at the university of Pennsylvania, proposed the gut-brain-skin unified theory. They found a close relationship between the brain and the skin. Recent studies demonstrate a mechanism among gut microbes unbalance, mental disorder and skin diseases, which has been postulated to the gut-brain-skin axis. Gut, brain and skin can interplay to each other. Psychological stress can aggravate a variety of skin diseases, particularly autoimmune skin disease, such as atopic dermatitis, psoriasis, seborrheic eczema, nodular prurigo, lichen planus, chronic urticaria, alopecia areata and pruritus sine material etc. Skin diseases are also closely related with health of digestive system. There are high ratio gastrointestinal patients who suffered from acne simultaneously. Gut microbiota is also involved in the gut-skin connection. The number of Bifidobacterium and Lactobacillus in feces are significantly less in adult patients with atopic dermatitis, than those of controls. The composition of aerobic and anaerobic bacteria in gut of those seborrheic dermatitis patients are severely changed. Similarly, more than half of acne patients go along with significant changes in the gut microbiota. Studies indicate that both gut microbiota and mental status affect the occurrence of skin diseases. On the contrary, the skin condition can also be as a barometer of mental health and gut microeubiosis. The treatment through the gut-brain-skin axis can be an important intervention to cure skin diseases. Combination of diet, probiotics, prebiotics, drug and mental health status can be positive factors in skin diseases therapy. Diet may affect the composition of gut microbes directly, and light diet can reduce the acne rate. Probiotics, like Bifidobacterium longum , Lactobacillus paracasei , Lactobacillus reuteri were reported to protect the function of intestinal barrier, help to reestablish intestinal microbiota ecological balance, and intensify the anti-inflammation effects. Some bacteria have tremendous potential in prevention and therapy of skin diseases, including eczema, allergic dermatitis, acne, allergic skin, UV induced skin damage and wound. Antibiotics can eliminate intestinal microbiota. Two weeks antibiotics treatment in mice may lead to reduce food intake, and messy, dull hair et al., in the opposite, 10 days probiotics drinking recover hair status obviously. Besides, probiotics can also restore the stress caused skin neurogenic inflammation in mice. In the present review, we aim to focus on the following hot topics around symbiosis microbiome, gut-brain-skin axis and skin diseases. To consider the gut microbiota, the brain and the skin as one combined system, instead of single reason may enhance the effects of treatment. More study should focus on the interaction of skin and intestinal microbiota, as well as the interaction mechanism of the gut-brain-skin axis, especially immune system. We urge scientists and medical doctors to pay more attentions on this field.