PUVA
PUVA is a Psoralen + UVA treatment for Eczema, Psoriasis and Vitiligo, and mycosis fungoides[1]. The Psoralen is applied or taken orally to sensitize the skin, then the skin is exposed to UVA. Long term use has been associated with higher rates of skin cancer.[2]
Psoralens are photosensitizing agents found in plants. They have been known since ancient Egypt but have only been available in a chemically synthesized form since the 1970s. Psoralens are taken systemically or can be applied directly to the skin. The psoralens allow a relatively lower dose of UVA to be used. When they are combined with exposure to UVA in PUVA, they are highly effective at clearing psoriasis. Like UVB light treatments, the reason remains unclear, though investigators speculate there may be similar effects on cell turnover and the skin's immune response.
Choosing the proper dose for PUVA is similar to the procedure followed with UVB. The physician can choose a dose based on the patient's skin type. Often, however, a small area of the patient's skin will be exposed to UVA after ingestion of psoralen. The dose of UVA that produces uniform redness 72 hours later, called the minimum phototoxic dose (MPD), becomes the starting dose for treatment.
Some patients experience nausea and itching after ingesting the psoralen compound. For these patients PUVA bath therapy may be a good option.