Cutaneous sensitivity to ultraviolet light and chemical irritants

This investigation examines the relationship between the sun sensitivity of human skin and its response to chemical irritants. Forty-four Caucasoid subjects with normal back skin were studied. The minimal erythema dose (MED) was determined with the sunburning spectrum of a high-pressure mercury lamp. Cutaneous irritability was quantified using a series of seven irritants of different chemical structure, solubility, and concentrations. The response was either expressed as a threshold value of exposure time (ammonium hydroxide, sodium hydroxide) or was graded after a standard exposure in intensity of whealing (dimethyl sulphoxide) or erythema (sodium lauryl sulphate, quaternium 1, croton oil, kerosene). A significant correlation between the MED and the response to all seven primary irritants was found. The relationship was better for water-soluble irritants than for lipid-soluble ones. Despite marked individual variations the determination of the MED is suggested as a valuable tool in identifying hyperirritable skin. Skin typing based on complexion and sunburn history proved to be less reliable.