Provided by: Healthwise

Treatment Overview

Phototherapy is the use of ultraviolet (UV) light to slow the rapid growth of new skin cells. This is helpful in treating psoriasis, which causes skin cells to grow too rapidly. There are two types of ultraviolet (UV) light therapy: ultraviolet B (UVB) and ultraviolet A (UVA).

Phototherapy may be given in a variety of places, such as in a hospital or doctor's office, in your home (UVB), or at a psoriasis day care center.

UVB light therapy may also be used alone, without drug treatment, for severe psoriasis. Typically, when medications for psoriasis are used with light therapy, you will use or take the medication first (apply it to your skin, take it by mouth, or take a bath in water that has the medication in it). Then you will go into a booth and be exposed to the UV light. (See psoralen and UVA light therapy [PUVA] for information about the combination of UVA light therapy and medications.) Combining treatments is called combination therapy. Two common combination therapies are:

• The Ingram regimen, which combines anthralin, coal tar products, and UVB phototherapy.
• The Goeckerman treatment, a combination of tar products with UVB phototherapy.

Your body is exposed to UV light from banks of light tubes that give off either UVB or UVA light in a booth. Booths come in a variety of designs. Some look like phone booths and you can stand in them. Others look like tanning beds and allow you to lie down during treatment. The booth will record the total amount of light you are exposed to.

In general, your entire body is exposed to the light. (If psoriasis affects only certain areas of your body, UV light may be directed at these selected areas only.) You will wear sunglasses that block UV light and goggles or a blindfold to protect your eyes from developing cataracts. Men may also need to shield their genitals to protect them from an increased risk of genital cancer.

One phototherapy option includes the use of narrow-band UVB light. This exposes you to only the wavelengths of light that are effective in treating psoriasis. Older UVB lights exposed the person being treated to ineffective wavelengths of light in addition to the effective wavelengths.

What To Expect After Treatment

As your skin recovers from treatment, it should be checked at least once or twice a year for signs of skin damage or skin cancer.

Why It Is Done

PUVA (the use of psoralen medications with UVA light therapy) is usually used when psoriasis is disabling and safer treatments have not worked.

UVB light alone (without drugs) is used for widespread plaque psoriasis and guttate psoriasis.

How Well It Works

Phototherapy is usually an effective treatment for psoriasis. 1 Partial to full skin clearing usually occurs after an average of 20 clinic treatments. More severe cases may require more treatments. Using home equipment, which is less powerful than clinic equipment, takes 40 to 60 sessions to clear the skin.

Doses of UVB high enough to cause the skin to turn red, used with Vaseline or other moisturizers, can clear psoriasis plaque.

When using UVA alone, treatments may be helpful but take much longer to clear psoriasis. UVA is very effective when used with a photosensitizing drug (psoralen), which is called PUVA.

Risks

Risks of phototherapy include:

• Skin cancer. UVB is the part of sunlight that causes suntans, sunburns, skin damage, and aging. Exposure to UVB light can also lead to skin cancer and can cause serious eye damage. The risk of skin cancer increases with the amount of exposure to UV light. Your dermatologist will monitor your overall exposure to UV rays.
• Skin damage. Long-term exposure to UVA light may lead to skin damage, aging, skin cancer, and cataracts. This risk of cataracts can be reduced by regular use of sunglasses that block UVA light when outdoors.
• Cancer. The male genitals are highly susceptible to the cancer-causing effects of both PUVA therapy and UVB therapy.

UVA produces fewer and milder short-term side effects than UVB.

What To Think About

Phototherapy requires a lot of time for treatment, and UV booth equipment is expensive. Commercial tanning beds, which emit UVA, are less effective for psoriasis than UV booths.

UV treatment for people with erythroderma or pustular psoriasis may make the condition worse.

The National Psoriasis Foundation can provide information on building a home UVB booth. They can also tell you where you can buy home light therapy equipment. Home light therapy should only be done under your doctor's supervision. For more information, see their Web site at www.psoriasis.org.

Complete the special treatment information form (PDF) (What is a PDF document?) to help you understand this treatment.

References

Citations

Habif TP, et al. (2005). Psoriasis and other papulosquamous diseases. In Skin Disease: Diagnosis and Treatment, pp. 106–115. Philadelphia: Elsevier Mosby.

Credits

• Author Shannon Erstad, MBA/MPH
• Editor Kathleen M. Ariss, MS
• Associate Editor Michele Cronen
• Primary Medical Reviewer Patrice Burgess, MD - Family Medicine
• Specialist Medical Reviewer Alexander H. Murray, MD, FRCPC - Dermatology