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If your psoriasis can't be controlled by medicine that you put on your skin, your doctor may suggest phototherapy, also known as light therapy. It uses ultraviolet rays -- from sunshine, artificial lamps, or lasers -- to slow the growth of your skin cells. That helps ease your symptoms.

Types of Phototherapy

Sunlight. Getting sun is a simple way to help your psoriasis. But that doesn’t mean you should go bake at the beach. Too much sun can give you a sunburn, which makes psoriasis worse and raises your risk of skin cancer.

If your doctor suggests that you try to get some sun each day, make sure you carefully control the amount. Typically, 20 minutes a day should be enough.

UVB (Ultraviolet B). You can get UVB rays from sunlight, especially summer noontime sun. But no matter what the time of day, sunlight also carries UVA rays, which can lead to cancer and speed up aging.

You can also get treated with UVB rays from a phototherapy unit at your doctor's office or at home.

Home ultraviolet lamps, however, can give off UVA rays as well.

You may need phototherapy treatments 3 to 5 days a week for 2 to 3 months.

Your doctor may suggest you combine UVB treatment with another therapy. For example, besides your lamp sessions, you can apply a cream made from coal tar to your skin. You may hear your doctor call this the "Goeckerman regimen."

Another combination therapy uses anthralin- salicylic acid paste along with ultraviolet treatment. Your doctor may refer to this as the "Ingram regimen."

PUVA (Psoralen plus Ultraviolet A). This combines ultraviolet A lamp sessions with a drug called psoralen, which you take as a pill or put on your skin as a cream. The drug makes your skin more sensitive to light. You might hear your doctor call this type of treatment “photochemotherapy.”

PUVA is particularly effective at clearing up severe psoriasis quickly and has long-lasting results. There are some side effects, though, including nausea, exhaustion, headaches, burning, and itching. Using PUVA over a long time can also raise your risk of skin cancer.

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