Skin pH mapping and its relationship with transepidermal water loss, hydration and disease severity in adult patients with atopic dermatitis.

Abstract

Defective skin's acidic mantle is a component of atopic dermatitis (AD) pathophysiology. We mapped the skin pH and determine its relationship with transepidermal water loss (TEWL), hydration and disease severity. A cross-sectional study involving patients aged ≥18years. Eczema Area and Severity Index (EASI) was assessed. Skin pH, TEWL and hydration were measured at 18 pre-determined sites. Forty-eight patients participated, 33(68.8%) females and 15(31.3%) males aged 28.46±12.07years. The overall skin pH was 5.32±0.68 ranging from 5.16±0.75 to 5.52±0.59. The lowest pH 5.16±0.75 was at anterior leg, popliteal fossae 5.18±0.67, lower back 5.21±0.64, forehead 5.22±0.62, upper back 5.25±0.65 and neck 5.26±0.76. Highest pH was at the cheek 5.52±0.59, anterior thigh 5.47±0.68, dorsal arm 5.46±0.68, volar arm 5.43±0.67 and abdomen 5.39±0.67. Lesional areas' pH (5.40±0.13) was higher than nonlesional (5.27±0.14), P=.01. pH at AD predilection sites was significantly lower non-predilection sites (5.26±0.59 vs 5.34±0.64). pH did not correlate with TEWL (r=.23, P=.12), EASI (r=.19, P=.20) and itch (r=.06, P=.70) but correlated with hydration r=-.33, P=.02. Skin pH was lower at AD predilection sites. There was no correlation between pH with AD severity and TEWL, pH correlated with hydration.