Comparison of Transepidermal Water Loss, Capacitance and pH Values in the Skin between Intrinsic and Extrinsic Atopic Dermatitis Patients

Atopic dermatitis (AD), with the prevalence rate of around 10 to 15%, is characterized by an intensely pruritic skin lesions with typical distribution and morphology. Recently, AD is divided into extrinsic type (ADe) and intrinsic type (ADi) according to the laboratory findings and associated diseases. ADe is well-known for high IgE level, positive response to food- or aero-allergens, whereas ADi has clinically similar skin lesions and distribution patterns of AD with normal serum IgE levels, negative in vitro test for environmental or food allergens and without associated atopic diseases. To instrumentally evaluate the differences of skin involvement and functions between ADi and ADe, we checked the transepidermal water loss (TEWL), capacitance and pH in both types of childhood AD and age-matched control. The proportion of ADi was around 20% in all AD patients (10/51). Our experiment suggested possible differences between ADi and ADe. Antecubital fossa is a famous involvement site of childhood type of AD, where both types of AD patients showed higher TEWL and decreased capacitance. ADe patients showed increased TEWL in all sites and lower hydration in 4 sites, whereas ADi patients showed no significant differences of TEWL and hydration in forehead, cheek, and back of leg.