Action Spectrum for Phototherapy of Psoriasis

Using a monochromator the action spectrum for ultraviolet phototherapy of psoriasis was determined for radiation between 254 and 313nm and compared to the action spectrum for erythema of uninvolved adjacent skin. Daily exposures of different doses of 254, 280, 290, 296, 300, 304 and 313nm radiation were observed. Wavelengths of 254, 280, and 290nm were erythemogenic but not therapeutic even at 10 to 50 times the minimal erythema dose. At the other wavelengths studied, the 2 action spectra were similar. In general, fixed daily doses cleared at lower cumulative dose than did incrementally increased daily doses. The small number of suberythemogenic exposure doses required suggests that monochromatic radiation may have advantages over broadband sources