Objective assessment of the skin of children affected by atopic dermatitis: a study of pH, capacitance and TEWL in eczematous and clinically uninvolved skin.

In order to obtain objective data on skin functions in subjects with atopic dermatitis (AD), according to the different phases of the disease, we evaluated the skin of children with AD instrumentally and compared it to that of healthy subjects of the same age group. One hundred patients, aged 3 to 12, and 21 healthy children were studied by means of measurements of pH, capacitance and transepidermal water loss (TEWL) at 8 different skin sites. At the moment of the investigation 55 children out of 100 presented skin lesions on at least one of the assessed skin areas, whereas 45 had been free from eczema for at least 1 month. Considering all skin sites together, significant differences were found between mean values of pH, capacitance and TEWL of eczematous skin, both in respect to those referring to apparently healthy skin in the same patients and in respect to the skin of control subjects. Moreover, TEWL, pH and capacitance values referring to uninvolved skin of AD patients significantly differed from those of healthy subjects. Finally, when values referring to patients with skin lesions and to patients without lesions were separately considered, significant differences concerning the parameters of uninvolved skin were observed. These data show that, in subjects with AD, skin functions undergo fluctuations according to the phase of the disease and support the hypothesis that the presence of active eczema determines an impairment of the barrier of uninvolved skin, even at sites far from active lesions.