[Effects of infrared and UVA rays on the human skin and their efficacy in the treatment of atopic dermatitis]

Abstract

Radiation with ultrared light (UR) and with a supposed pure UVA high pressure tube leads to increase of the skin surface temperature, which is linear during UR radiation and causes pain at 42 degrees C. During UVA radiation, the skin surface temperature increases in a parabolic curve and approximates 42.3 degrees C asymptotically. There is no pain. Following both UR and UVA, erythema occurs at 41.4 degrees C. UVA additionally results in immediate pigmentation dependent on the dose between 6 and 20 J/cm2. UR does not induce any pigmentation. The erythema induced by UR disappears completely within 6 hours. Corresponding to the dose, the erythema persists up to 7 days after UV radiation. Immediate and delayed erythema obviously overlap. The pigmentation shows a biphasic reaction. There is a maximum immediately at the end of UV radiation, reduction between 6 and 24 hours after radiation. The course of erythema and pigmentation indicates a clinically relevant part of UVB in the emission spectrum supposed to be pure UVA. A therapeutical trial was performed in 40 patients suffering from severe atopic dermatitis. In a group of 10 patients, daily UR radiation up to beginning pain showed good results within 3 weeks. The therapeutic effects were even better in another group of patients radiated with suberythematous doses of UVA daily for the same time. UVA radiations twice a week for 6 to 8 weeks were less effective.