Skin care by washing with water is not inferior to washing with a cleanser in children with atopic dermatitis in remission in summer: WASH study

Background: Washing with water is not inferior to washing with soaps and detergents in children with atopic dermatitis (AD) in remission during the fall-winter seasons. We investigated whether this finding varies during summer based on the type of cleanser (soaps and detergents). Methods: This evaluator-blinded, pragmatic, randomized, and non-inferiority study enrolled patients with AD whose eczema was controlled following regular steroid ointment application 2 days/week. For 8 +/- 4 weeks, participants washed their upper and lower limbs with a cleanser on one side and with water alone on the other. Each participant chose either a weakly alkaline soap or an acidic detergent. The primary outcome was the Eczema Area and Severity Index (EASI) score at week 8 +/- 4. Results: The data of 43 of the 47 registered participants were analyzed. The median patient age was 44 (23-99) months; 28 and 15 participants chose weakly alkaline and acidic cleansers, respectively. At week 8 +/- 4, EASI scores of the water and cleanser sides were 0.00 (0.00-0.40) and 0.15 (0.00-0.40), respectively (p = 0.74). The difference between both sides was 0.00 (-0.07 to 0.14); the limits of the 95 % confidence interval did not reach the pre-specified non-inferiority margin. No difference was observed in the median Patient-Oriented Eczema Measure score, number of additional steroid ointment applications, and occurrences of skin infections. There were no differences between the cleanser types in any of the results. Conclusions: We demonstrated that washing with water was not inferior to that with a cleanser in patients with AD in the maintenance phase during summer, regardless of the type of cleanser. (c) 2024 Japanese Society of Allergology. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).