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:
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. Broadband UVB therapy uses a wider range of wavelengths.
A laser treatment for psoriasis (excimer laser) also uses UVB light. Excimer laser works well for psoriasis that has been hard to treat on the elbows and knees.1
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
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
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.
PUVA (the use of psoralen medicines with UVA light therapy) is
usually used when psoriasis is disabling and safer treatments have not
UVB light alone (without drugs) is used for widespread
plaque psoriasis and
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:
UVA produces fewer and milder short-term side effects than
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.
For people who have
erythroderma or pustular psoriasis, UV treatment may make the
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 website at
Complete the special treatment information form (PDF)(What is a PDF document?) to help you understand this treatment.
Gudjonsson JE, Elder JT (2008). Psoriasis. In K Wolff et al., eds., Fitzpatrick's Dermatology in General Medicine, 7th ed., vol. 1, pp. 169–193. New York:
Habif TP, et al. (2011). Psoriasis and other papulosquamous diseases. In Skin Disease: Diagnosis and Treatment, 3rd ed., pp. 120–153. Edinburgh: Saunders.
August 5, 2013
Adam Husney, MD - Family Medicine
& Amy McMichael, MD - Dermatology
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