A psoralen medication (medical name methoxsalen) is taken 1½ to 2 hours before you are exposed to ultraviolet A (UVA) light (PUVA).  Psoralens may be taken orally or topically (applied as lotion or by bathing in medicated water).   Psoralens that are put into bath water cause greater sensitivity to UVA than the oral medication, so lower doses of UVA can be used.  PUVA treatment is repeated 2 to 3 times a week.  As treatment progresses, the dose of medication is not increased, but the amount of light may be increased.

Goggles should be worn to protect eyes during the UVA treatment. Separate UVA-blocking glasses should be worn for 24 hours after PUVA therapy. Men should protect their genitals from UVA exposure during treatments.

Why PUVA?

Psoralens increase the skin's sensitivity to UV light, so they are used to improve the effectiveness of UV light therapy for psoriasis. It is thought that PUVA therapy reduces the excess growth of skin cells.  PUVA is used to treat moderate to severe psoriasis (covering more than 20 % of the skin).  PUVA is used to treat psoriasis that has not responded to other treatments.

Side Effects

Short-term side effects when using PUVA to treat psoriasis include skin redness, headache, nausea, itching, burning, the spread of psoriasis to skin that was not affected before, nausea from the medication, and squamous cell carcinoma.

Long-term side effects when using PUVA to treat psoriasis include:

• Premature skin damage associated with sun exposure.
• Discolored spots on the skin.
• Overgrowth of the scaly layer of skin caused by exposure to sunlight (actinic keratosis).
• Nonmelanoma skin cancer.
• Cataracts. Cataracts may be avoided by wearing goggles during UVA treatments and sunglasses that block UV light when outdoors.