Photodynamic therapy (PDT) is commonly used to treat actinic keratoses, superficial cutaneous carcinoma, photodamage, and/or acne. The aim of this study was to compare the usefulness of Avène thermal spring water (ATSW), a low mineral content spring water, to a high mineral content spring water. We evaluated post-PDT clinical symptoms and findings when used as an adjunctive therapy in postprocedure skin care.