Phototherapy for Psoriasis

Phototherapy, or light therapy, is typically prescribed by a dermatologist. Phototherapy involves exposing the skin to ultraviolet light on a regular basis and under medical supervision. Treatments can be done in a health care provider's office, a clinic, or at home with a phototherapy unit. The key to success with light therapy is consistency.

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Types of Phototherapy

  • UVB
  • PUVA

Ultraviolet light B (UVB)

UVB is present in natural sunlight and is an effective treatment for psoriasis. UVB penetrates the skin and slows the growth of affected skin cells. Treatment using UVB can include UVB phototherapy, excimer laser, or in-office or home UVB phototherapy.

UVB phototherapy treatment involves exposing the skin to an artificial UVB light source for a set length of time on a regular schedule. This treatment is administered in a health care provider’s office or clinic or at home with a phototherapy unit.

There are two types of UVB treatment:

  1. Broad band
  2. Narrow band

There are three main differences between them:

  1. Narrow-band UVB light bulbs release a smaller range of ultraviolet light
  2. Narrow-band UVB may clear psoriasis faster and produce longer remissions
  3. Narrow-band UVB may require fewer treatments per week

Methods of UVB Treatment

  1. Localized units
  2. Excimer laser
  3. Home treatment

Localized Units

UVB treatment is offered in different ways. This can include small units for localized areas such as the hands and feet, full-body units, or hand-held units. Some UVB units use traditional UV lamps or bulbs, others use LED bulbs.

Excimer Laser

The excimer laser, approved by the Food and Drug Administration (FDA) for treating chronic, localized psoriasis plaques, emits a high-intensity beam of UVB.

The excimer laser can target areas of the skin affected by mild-to-moderate psoriasis. Research indicates it is a particularly effective treatment for scalp psoriasis. However, there is not yet enough long-term data to indicate how long improvements will last following a course of laser therapy.

Home Phototherapy Treatment 

Treating psoriasis with home UVB phototherapy can be an economical and convenient choice. Like phototherapy in a health care provider’s office or clinic, it requires a consistent treatment schedule. Individuals are treated initially at a medical facility and then begin using a light unit at home. It is critical when doing phototherapy at home to follow a health care provider’s instructions and continue with regular check-ups.

All phototherapy treatments, including the purchase of equipment for home use, require a prescription from your health care provider.

Psoralen + UVA (PUVA) 

Ultraviolet light A (UVA) is relatively ineffective for psoriasis unless it is used with light-sensitizing agents called psoralens. This process, called PUVA, slows down excessive skin cell growth and can clear psoriasis symptoms for varying periods of time.

Stable plaque psoriasis, guttate psoriasis, and psoriasis of the palms and soles are most responsive to PUVA treatment.

There are three administration routes for PUVA:

  1. Topically as a cream
  2. Mixed in with bathwater
  3. Ingested orally


Although both UVB and UVA are found in sunlight, UVB works best for psoriasis. UVB from the sun works the same way as UVB in phototherapy treatments.

However, using sunlight to treat psoriasis is not recommended for everyone. Sunlight is not as effective for the treatment of psoriasis as prescription phototherapy. Talk with your health care provider to find out if treating with sunlight is right for you.

Some topical medications can increase the risk of sunburn. These include tazarotene and coal tar. Individuals using these products should talk with their health care provider before going out in the sun.

People who are using PUVA (see below) or other forms of light therapy should limit or avoid exposure to natural sunlight unless directed by a health care provider.

The Risks of Tanning Beds

Some people visit tanning salons as an alternative to natural sunlight. Tanning beds in commercial salons emit mostly UVA light, not UVB. The beneficial effect for psoriasis is attributed primarily to UVB light. 

NPF does not support the use of indoor tanning beds as a substitute for phototherapy performed with a prescription and under a health care provider’s supervision.

The American Academy of Dermatology (AAD), the FDA, and the Centers for Disease Control and Prevention all discourage the use of tanning beds and sun lamps. Indoor tanning raises the risk of melanoma by 59 percent, according to the AAD and the World Health Organization. In May 2014, the FDA reclassified sunlamps (which are used in tanning beds and booths) from Class I (low risk) to Class II (moderate risk) products.

Bottom line: The ultraviolet radiation from tanning beds and sun lamps can damage the skin, cause premature aging, and increase the risk of skin cancer.

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Phototherapy for Psoriasis Side Effects 

While phototherapy has shown high success rates in improving psoriasis symptoms, it is essential to be aware of potential side effects. These may include redness, stinging, burns, and an increased risk of skin cancer. Patients should thoroughly discuss these risks with their health care provider to make informed decisions about their treatment plan.

Frequently Asked Questions

Is light therapy good for psoriasis?

Light therapy, specifically UVB (Ultraviolet B) and PUVA (Psoralen + Ultraviolet A), is considered effective for treating psoriasis. UVB slows the growth of affected skin cells, while PUVA uses UVA with light-sensitizing agents to control excessive skin cell growth in psoriasis. 

It's important to consult with a health care provider to determine the most suitable treatment approach for you.

Is phototherapy better than sunlight for psoriasis?

Sunlight contains both UVB and UVA, but UVB is considered more effective for treating psoriasis. Prescription phototherapy is generally recommended over sunlight, as it allows for controlled and consistent exposure. 

Sunlight may not be as effective, and some medications used in psoriasis treatment can increase the risk of sunburn. It's important to consult with a health care provider to determine the most suitable treatment approach for you. 

Can I donate my old home phototherapy unit?

Unfortunately, we can’t legally help with the sale or donation of your used phototherapy unit. In the U.S., phototherapeutic light units are available only by prescription, and the same laws apply to them as would any other prescription. 

U.S. Code of Federal Regulations Title 21, section 801.109 states that it is illegal to sell, trade, or in any way distribute a phototherapeutic light unit unless legally licensed to do so by the FDA. Under this law, only a physician or licensed light manufacturer or distributor is considered eligible to facilitate the sale or trade of a phototherapeutic light unit. 

You can contact the manufacturer of your phototherapy unit if you would like information on how to recycle the unit. 

Questions about Phototherapy?

Get your free phototherapy booklet for more information and tips for effective phototherapy treatment.

Request your booklet today

Last updated on 3/19/2024 by the National Psoriasis Foundation.

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