Hydrobiome of Thermal Waters: Potential Use in Dermocosmetics

Over the course of the last 20 years, numerous studies have identified the benefits of thermal waters on different skin conditions. Consequently, several investigations have been carried out on their effects on the skin, which are linked to their chemical composition, and, recently, scientists have turned their attention to the role of the thermal spring's microbiota, named "hydrobiome", regarding these therapeutic effects. At the same time, the development of cosmetics based on pre, pro, and postbiotics has reached great relevance and research is increasing every day. This review gathers information on the biological diversity of thermal spring waters and their potential use in obtaining biological compounds, metabolites, or bacterial extracts for use in dermocosmetics as active ingredients. These bioactive compounds are able to improve dermatological diseases such as atopic dermatitis or rosacea and ameliorate pruritus and xerosis; moreover, they can increase protection against UV exposure, strengthen barrier function, maintain good homeostasis of skin defenses, repair damaged skin, promote wound healing, improve skin condition, reduce uneven skin pigmentation, and prevent skin aging. From a future perspective, fruitful cooperation among researchers, hydrologists, thermal spa centers, and cosmetic industries will drive this sector toward a better understanding of the role of the hydrobiome of thermal spring waters on healthy skin and dermatological diseases and consider the inclusion of derivatives of this hydrobiome (in the form of fermenters, lysates, extracts, etc.) in dermocosmetic formulations. Therefore, and being aware of the potential of the hydrobiome in dermatological and skin care applications, the future prospects for the use of bioactive substances derived from it in dermocosmetic formulations are promising.