How it works
UV-ray phototherapy is one of the main treatments of vitiligo. It uses UV rays, i.e. short waves which are closer to the lower part of visible sunlight.
This range of waves includes energetic particles (photons) majorly interacting with the skin cells (melanocytes) which are sensitive to them. Phototherapy uses generators (lamps) reproducing the same electromagnetic UVA and UVB wideband waves of sunlight and, lately, narrowband UVB rays 311 nm. Its density or pressure on the skin surface is measured in joules on squared centimeters for one second of time, i.e. watt (ultraviolet power measured on skin exposed to irradiation), for seconds (exposure time), for square centimeters (irradiated surface).
Being the whole body surface fifteen to twenty thousand square centimeters on average, in accordance with height and structure of each person, the range of generically used waves -as for sunlamps, used in cosmetics- is a very high UV intake (dose) for the skin, due to the irradiation’s pressure on all its area.