Instrumental evaluation of subclinical responses to 0.05% NiSO(4) patch tests.

Abstract

The possibility of identifying allergic reactions while they are not clinically evident could prove extremely useful in studying the evolution of skin responses in experimentally-induced contact dermatitis. In drug research and in cosmetological research, the sensitizing properties of new molecules or haptens present in the product in a low concentration also need be clarified. The object of the present study was to validate noninvasive techniques and their use for the study of subclinical allergic reactions. 70 nickel-sensitized subjects previously standard tested with 5% nickel sulphate in petrolatum were challenged with a 0.05% nickel sulfate solution on the volar aspect of the forearm, application for 24 h and measurement at 72 h. Colorimetry, evaporimetry (transepidermal water loss, TEWL) and high-frequency echography were used to characterize reactions. Colorimetry and TEWL did not show any significant differences between patch test areas and control areas. Skin thickness determination, conversely, evidenced a significant increase both with respect to baseline values and control areas. Echographic evaluation is able to detect modification of skin thickness of subclinical allergic patch test reactions to nickel sulfate while colorimetry and TEWL failed to detected such minute changes.