Phototherapy

Phototherapy or light therapy, involves exposing the skin to ultraviolet light on a regular basis and under medical supervision. The key to success with light therapy is consistency.
Ultraviolet light B (UVB)/Ultraviolet light A (UVA) Treatment
UVB Phototherapy
Present in natural sunlight, UVB is an effective treatment for psoriasis and other skin conditions. UVB penetrates the skin and slows the growth of affected skin cells. Treatment involves exposing the skin to an artificial UVB light source for a set length of time on a regular schedule.
During UVB treatment, your condition may worsen temporarily before improving. The skin may redden and itch from exposure to the UVB light. To avoid further irritation, the amount of UVB administered may need to be reduced. Occasionally, temporary flares occur with low-level doses of UVB. These reactions tend to resolve with continued treatment.

UVB can be combined with other topical and/or systemic agents to enhance efficacy, but some of these may increase photosensitivity and burning, or shorten remission. Combining UVB with systemic therapies may increase efficacy dramatically and allow for lower doses of the systemic medication to be used.
 
Psoralen + UVA (PUVA)
 
 
Like UVB, ultraviolet light A (UVA) is present in sunlight. Unlike UVB, UVA is relatively ineffective unless used with a light-sensitizing medication psoralen, which is administered topically or orally. This process, called PUVA, slows down excessive skin cell growth and can clear psoriasis symptoms for varying periods of time.

The most common short-term side effects of PUVA are nausea, itching and redness of the skin. Drinking milk or ginger ale, taking ginger supplements or eating while taking oral psoralen may prevent nausea. Antihistamines, baths with colloidal oatmeal products or application of topical products with capsaicin may help relieve itching. Swelling of the legs from standing during PUVA treatment may be relieved by wearing support hose.