Thermal Therapy Modulation of the Psoriasis-Associated Skin and Gut Microbiome.

Psoriasis is an immune-mediated disease primarily manifesting as skin redness and inflammation that affects 2­3% of the world's population. No cure is currently available for this condition, and patients are offered pharmacological and non-pharmacological options to alleviate the discomfort. Previous studies and clinical practice have shown that thermal water treatment can be a non-pharmacological option to reduce the areas affected by the disease. However, the specific mechanisms causing this reduction have not been clarified yet. Given that neither the chemical nor the physical composition of thermal water can explain this beneficial effect, recent studies have suggested that it might be due to the effect of thermal water on the microbial communities living on the skin (i.e., the skin microbiome). In this work carried out at Terme di Comano, Northern Italy, we describe the effect of thermal water treatment on the skin microbiome of patients with psoriasis and we highlight the potentially beneficial effect of thermal water drinking on the microbial communities living in the gut, namely the gut microbiome. Specifically, we show that after balneotherapy the areas affected by psoriasis have a higher diversity of microbes usually present on healthy skin, potentially explaining the reduction in disease severity after treatment, and we describe how the gut microbiome of patients who drank thermal water changes to host more species linked with favorable metabolic health. These findings highlight that thermal water treatment and drinking could reduce both the skin and systemic symptomatology of psoriasis by affecting the skin and gut microbiome.