Thermal Spring Waters as Cosmeceuticals: An Update

Thermal spring waters (TSWs) have long been used in dermatology for chronic inflammatory dermatoses and sensitive skin and are increasingly positioned as cosmeceutical active ingredients. This review summarizes studies on the use of TSW and their hydrobiome derivatives in dermocosmetics and cosmeceuticals for skin health. TSW exhibits anti-inflammatory, antioxidant, soothing, hydrating and barrier-restoring effects in vitro, ex vivo and in clinical studies, improving conditions such as atopic dermatitis, psoriasis, acne, sensitive skin, radiation dermatitis and post-procedure erythema. In parallel, the hydrobiome of TSW has enabled the development of postbiotic and paraprobiotic ingredients, which modulate skin immunity, microbiota, barrier function and clinical signs of inflammatory and sensitive skin. Despite robust preclinical and growing clinical evidence, cosmeceuticals remain regulated as cosmetics in most regions, highlighting the need for specific regulatory frameworks and standardized approaches to demonstrate the safety and efficacy of TSW-based cosmeceuticals, as well as defining acceptable claim categories and minimum evidence thresholds.