Comparative Effect of Soft, Hard and Chlorinated Water on Atopic Skin and Clinical Benefits of a Dermocosmetic Routine

Background: Epidemiological data link hard and chlorinated water to atopic dermatitis (AD), but experimental evidence on their effect and on dermocosmetic benefit remains limited. Objectives: We aimed to compare the effects of soft, hard, and chlorinated water on atopic skin and assess whether a dermocosmetic routine mitigates these effects. Methods: In a 3-day, open-label, intra-individual study, 66 adults with atopic skin underwent repeated forearm immersions (five cycles/day) in soft, hard, or chlorinated water. One forearm received a cleansing-oil and moisturising-balm routine after each cycle; the contralateral forearm served as untreated control. TEWL, hydration, and global discomfort were assessed. In a 21-day real-life study, adults with AD regularly exposed to hard domestic or swimming-pool water used the routine daily. Discomfort and quality of life were recorded. Results: Water immersion induced modest, inconsistent TEWL changes, increased hydration and slightly reduced discomfort, without differences between water types. The routine reduced TEWL, increased hydration, and decreased discomfort for all water types. In real life, it produced immediate and sustained improvements in discomfort and quality of life. Conclusions: Under controlled exposure, soft, hard, and chlorinated water exert comparable, limited effects on atopic skin. The dermocosmetic routine consistently improves barrier-related parameters and comfort, independently of water type.