SODIUM HYDROXIDE-INDUCED IRRITANT DERMATITIS AS ASSESSED BY COMPUTERIZED ELABORATION OF 20-MHZ B-SCAN IMAGES AND BY TEWL MEASUREMENT - A METHOD FOR INVESTIGATING SKIN BARRIER FUNCTION

Sodium hydroxide-induced irritation was studied in 34 volunteers, by m eans of 24-h patch testing at different concentrations, and by a 10-mi n testing procedure employing 0.1 mol/l NaOH. As a supplement to subje ctive evaluation of skin changes, assessments of test areas by TEWL me asurement and sonography were performed at 24, 48 and 72 h. After 24-h patch testing, instrumental evaluations showed an increase in the ext ension of the hypo-echogenic dermal area and in TEWL, whereas a 10-min NaOH application induced a decrease of the dermal and epidermal refle ctivity and an increase in TEWL. Twenty-four hour patch testing with 4 % NaOH allowed a classification of subjects into two categories: subje cts who reacted normally and hyper-reactors. Hyper-reactors showed an enhanced inflammatory response and a more pronounced barrier function damage, as assessed clinically and instrumentally by decreased dermal reflectivity, and by higher postexposure TEWL. Subjects with a more ma rked inflammatory response to 4% NaOH also showed greater TEWL increas es during the short-term testing procedure employing 0.1 mol/l NaOH. M oreover, these subjects were characterized by higher baseline TEWL val ues, indicating that cutaneous reactivity to NaOH is at least partly c orrelated to impaired stratum corneum function, which is inadequate to effectively prevent compounds from penetrating the skin.