[Principles and technicals studies of investigating photosensitivity of the skin (author's transl)].

The authors report the principles of investigating photosensitivity of the skin: objects of testing and some basic practical consideration (doses, laws of irradiance, choice of wavelength in a test). Artificial sources for irradiation are studied. Xenon arc lamp is the most suitable. Two main kinds of device are suitable for routine radiant energy measurement; the thermopile with linear spectral response and the photoelectric cells without linear relationship between wavelength and sensitivity. To delimit the emission of xenon arc, the authors use absorption filters (cut-off type). Irradiation monochromator is indispensable to much dermatological photobiology, especially action spectrum study. Methods of measurement, time course of the response dose response relationship, threshold response and action spectrum of normal and abnormal effects of light on the skin are described. Routine phototesting procedure enclose: minimal erythemal dose, phototest, photopatchtest. Technical study and interpretation are exposed. For the dermatologist, phototesting procedure is necessary for the diagnosis. Mechanism of photosensitivity (phototoxic or photoallergic reaction) and wavelength dependence have to be known for an appropriate treatment.