Comparative Impact of Hard and Chlorinated Water on Biometrological Parameters of Atopic Skin and the Clinical Benefits of Dermocosmetic Routine Interventions

Background: Epidemiological studies have established a positive association between water hardness, chlorine content, and the prevalence or severity of atopic dermatitis (AD). These environmental factors are known to exacerbate skin barrier dysfunction and increase discomfort in individuals with atopy-prone skin. Objectives: This research aimed to objectify the detrimental effects of hard and chlorinated water on atopic skin, both under controlled experimental conditions and in real-life settings. The studies assessed the efficacy of a daily dermocosmetic routine (comprising a cleanser and moisturizer adapted for atopy-prone skin) for reducing water-induced discomfort and improving the quality of life. Methods: Three clinical studies were conducted: one experimental comparative study of repeated washing or immersion with hard, chlorinated, and soft water, and two intra-individual 21-day studies on hard water and swimming pool water (chlorinated) exposure in real-life conditions. Results: Cumulative exposure to hard water (HW) and chlorinated water (CW) increased TEWL, while soft water (SW) had no significant effect on barrier function. The dermocosmetic routine significantly improved skin hydration and barrier function, with TEWL significantly decreasing by 25% (HW), 17% (CW), and 20% (SW) compared to untreated areas. In real-life studies, 21-day use of the products significantly reduced skin discomfort and improved quality of life. Conclusion: Repeated exposure to hard and chlorinated water can exacerbate skin discomfort and clinical symptoms of atopic dermatitis. An adapted daily dermocosmetic routine can significantly mitigate these effects, improving barrier function, skin comfort, and daily quality of life.