STUDIES OF AN URTICARIAL RESPONSE TO BLUE AND VIOLET LIGHT IN MAN

Abstract

Photo-physiological studies of an urticarial response elicited by blue and violet light demonstrate the following: The reciprocity law is obeyed. A photo-reaction having a Qio of 1.3-1.4, and a thermal reaction with variable temp. characteristics, are involved. The latter is probably the response of the minute skin vessels to a histamine-like substance. All parts of the body are sensitive to light, but the degree of sensitivity varies from region to region; the exposed parts are least sensitive. Sensitivity fluctuates but has shown no general trend in 10 months. Determination of the spectral sensitivity suggests that the sensitizer is a carotinoid pigment; the possible origin of such a pigment is discussed.