Most patients improve with natural sunlight and should be encouraged to sunbathe. During the winter, courses of artificial ultraviolet radiation (UVB), as an outpatient or at home, may help (Fig. 5.17). Both broadband UVB and narrow band UVB (311 nm) can be used. Treatments should be given by an expert, twice to three times weekly for 8 weeks. Goggles should be worn. The initial dose is calculated either by establishing the skin type or by determining the minimal dose of UVB that causes erythema in a test patch 24 h after radiation.
The initial small dose is increased incrementally after each exposure providing it is well tolerated. The number of treatments and doses employed should be recorded. The main risk of UVB therapies in the short term is acute phototoxicity (sunburn-like reaction) and, in the long term, the induction of skin cancer.