A New Apparatus with High Radiation Energy Between 320–460 nm: Physical Description and Dermatological Applications

A new apparatus (UVASUN 5000) is presented with high radiation energy between 320–460nm. The measurable energy below 320nm was shown to be many orders of magnitude too low to produce erythema. The radiator is a specially developed source for high UV-A intensity, housing a quartz bulb with a mixture of argon, mercury and metal-halides. At a skin-target distance of 0.2m the size of the irradiated area is 0.35 × 0.35 m, and the measured mean UV-A intensity is about 1400 W•m−2 (140 mW•cm−2). The UV-A energy in the range of 320–400nm is about 84% of the total radiation energy.Effects of very high doses of UV-A on human skin were studied. Following single UV-A applications the minimal tanning dose UV-A (Mth) and the immediate pigment darkening (IPD) dose of UV-A were established. The calculated IPD threshold time was 1.8mm at 0.2m. Repeated exposure to this UV-A delivering system yields long lasting dark brown skin pigmentation without any clinical or histological signs of “sunburn” (UV-B) damage, epidermal hyperplasia or thickening of the stratum corneum.The instrument was also successfully used for photo-patch testing and reproduction of skin lesions of polymorphous light eruption. Minimal therapeutic results were seen in the phototherapy of vitiligo and inflammatory acne