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)
UVB light is more effective than UVA light for treating
Phototherapy can be used alone or with medicines. UVB light
therapy is used alone to treat severe psoriasis. Typically, when medicines for
psoriasis are used with light therapy, you will use or take the medicine first.
You may apply it to your skin, take it by mouth, or use it as bath salts in
water. Then you will go into a booth and be exposed to the UV light. Using two
kinds of treatment is called combination therapy. Three common combination
The Ingram regimen, which combines
coal tar products, and UVB phototherapy.
treatment, a combination of
tar products and 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 several
designs. Some look like phone booths and you can stand in them. Others look
like tanning beds and you can 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 getting cataracts. Men may also
need to shield their genitals to protect them from an increased risk of genital
One phototherapy option includes the use of narrow-band UVB light.
This exposes you to only the wavelengths of light that work for
treating psoriasis. Older UVB lights exposed the person being treated to
ineffective wavelengths of light in addition to the effective
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 medicines with UVA light therapy) is
usually used when psoriasis is disabling and safer treatments have not
Phototherapy is usually an effective treatment for
psoriasis.2 Partial to full skin clearing occurs after
an average of 20 clinic treatments. More severe psoriasis may require more
treatments. Using home equipment, which is less powerful than equipment at a
clinic, takes 40 to 60 sessions to clear the skin.
Doses of UVB high enough to cause the skin to turn red, used with
petroleum jelly (such as Vaseline) or other moisturizers, can clear psoriasis
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). This combination treatment is called PUVA.
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.
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 you are 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
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.
The National Psoriasis Foundation provides information on
where you can buy home light
therapy equipment. Home light therapy should only be done under your doctor's
supervision. For more information, see the organization's Web site at
Koek MBG, et al. (2009). Home versus outpatient ultraviolet B phototherapy for mild to severe psoriasis: Pragmatic multicentre randomised controlled non-inferiority trial (PLUTO study). British Medical Journal, 338: b1542.
Habif TP, et al. (2005). Psoriasis and other
papulosquamous diseases. In Skin Disease: Diagnosis and Treatment, pp. 106–115. Philadelphia: Elsevier Mosby.
Primary Medical Reviewer
Kathleen Romito, MD - Family Medicine
Specialist Medical Reviewer
Alexander H. Murray, MD, FRCPC - Dermatology
January 6, 2010
WebMD Medical Reference from Healthwise
January 06, 2010
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