Avène Thermal Spring Water (TSW) is a natural active component characterized by a low mineral content. In vitro experiments have demonstrated the effect of Avène TSW on membrane fluidity, its antiradical and anti-inflammatory properties, its effects on many mediators involved in the immune response and its stimulating effect on keratinocyte differentiation. The clinical efficacy of the water was demonstrated at the hydrotherapy centre in chronic and disabling diseases such as atopic dermatitis but also in various settings in medical and post dermatology procedure such as photodynamic therapy or photothermolysis. All these data support the fact that the Avène TSW is an active component.