Children's soap pH analysis and its meaning in children's skin cleansing

The aim of this study was to evaluate the surface hydrogen potential (pH) values of children's soaps to identify those with a pH closer to the physiological one (5.0-5.5) and describe the most prevalent surfactants in the sample.

This was a observational, analytical, cross-sectional, and quantitative study that included 96 cleansing products intended for children's or sensitive skin, available at over-the-counter sales points in a Brazilian capital. The pH of the samples was measured after dilution to 1% in distilled water. A total of 34 bar soaps and 62 liquid soaps (including 20 syndets) were analyzed. Descriptive statistics and Student's t-test were used to analyze the differences between the groups, with a minimum significance level of 5%. The surfactants present in the products were listed, and the most prevalent were identified.

The pH of the products ranged from 4.54 to 11.01, with a mean of 7.80±1.90. The pH levels differed between the liquid and bar formulations (4.54-8.00 vs. 8.01-11.01, respectively; p<0.001). The syndets had pH values closer to the physiological range (4.99-7.78), with lower values when compared to liquid soaps (p<0.001). The most prevalent surfactant in the sample was cocamidopropyl betaine.

Bar soaps do not have a pH suitable for children's skin cleansing, whereas liquid soaps, particularly syndets, have a pH closer to the physiological range. Knowledge of the pH values of children's cleansing products by health professionals and caregivers is important, given the wide variety found in this study and the lack of reliable information on the packaging of most products.