Washing with water alone versus soap in maintaining remission of eczema

There is no consensus on the use of soap in skin care for atopic dermatitis in Japan. Thus, this study aimed to evaluate the efficacy of soap to maintain eczema remission in atopic dermatitis patients during the fall-winter period in Japan.

This assessor-blinded, pragmatic randomized, non-inferiority study enrolled atopic dermatitis patients whose eczema was controlled by regular steroid ointment application less than or equal to 2 days / week (tacrolimus ointment was permitted). For 8 ± 3 weeks, participants washed their upper and lower limbs on one side with soap (soap side) and on the other side with water alone (water side). The primary outcome was an Eczema Area and Severity Index score at week 8 ± 3.

Twenty-nine participants were analyzed. The Eczema Area and Severity Index scores at week 8 ± 3 of the water and soap sides were 0.0 (0.0-0.4) and 0.0 (0.0-0.4), respectively (P = 0.18). The difference between both sides was -0.02 (-0.11-0.08), and the limits of the 95% confidence interval did not reach the prespecified non-inferiority margin. The average Patient-Oriented Eczema Measure score was 1.27 ± 1.7 and 1.32 ± 1.8 for the water and soap sides, respectively (P = 0.92). The total number of additional steroid ointment applications was four (0-20) times and six (0-23) times, respectively (P = 0.98). Participants were categorized according to self-assessments of the usefulness of soap, with 2, 24, and 3 participants in the water-effective, invariant, and soap-effective groups, respectively.

For children with controlled atopic dermatitis, washing with water alone was not inferior to washing with soap for maintaining remission of eczema during the fall-winter period in Japan.