Phototherapy is the use of light to treat psoriasis, vitiligo, and other skin disorders. In treatments, the skin is exposed to a special type of light which comes from a medical device commonly referred to as a phototherapy unit. These units range from hand-held and table-top devices for spot treatment of small areas to cabinet or “walk-in” units for patients requiring full body treatment. The medical lamps in these phototherapy units emit ultraviolet (UV) light in a wavelength that creates changes within the skin cells. The cells in most patients then begin to behave normally, which reduces or eliminates the symptoms of the skin disease.