Psoriasis - Phototherapy

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• Treatment starts in the doctor's office or another medical setting. Once the disease has stabilized, the patient can get a prescription for equipment that can be used at home. Research finds that home UVB treatment is just as safe and effective as hospital-based treatment, and patients may be more likely to get the treatments they need if they administer them at home. Even at home, treatment must always be supervised.
• In preparation, the patient fully undresses, although unaffected areas may be covered to avoid overexposure.
• The initial session may last for just a few seconds, depending on whether the patient has lighter or darker skin. The lightest skin is exposed to the briefest session. The duration increases with each treatment until the skin clears or the patient experiences itching or irritation. The condition may worsen initially.
• UVB therapy usually requires about 20 - 40 treatments (about three per week). Full results take about 3 weeks.

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Use of Medication. UVB was commonly used with coal tar (the Goeckerman regimen) in past decades, and then with anthralin (the Ingram regimen). Other medications are being studied with some success, and may prove to be better tolerated.

The Goeckerman regimen requires daily treatments for up to 4 weeks. The coal tar or anthralin is applied once or twice each day and then washed off before the procedure. Studies indicate that a low-dose (1%) coal tar preparation is as effective as a high-dose (6%) preparation. Such regimens are unpleasant, but are still useful for some patients with severe psoriasis, because they can achieve long-term remission (up to 6 - 12 months).

Some evidence suggests that using a simple emollient (such as Vaseline or mineral oil) that enhances UVB light penetration can be effective. This addition to the treatment increases the risk for sunburns, however, and patients must be careful to avoid sun exposure. Researchers are trying combinations of other topical and oral medications. For example, combining UVB with methotrexate or retinoids such as a tazarotene gel or oral acitretin is producing positive results. Combinations with any of these drugs, however, must be supervised carefully to avoid serious reactions.

Side Effects of UVB. The treatment can cause itching and redness. UVB radiation from sunlight is known to increase the risk for skin cancers. There is no strong evidence that UVB treatments pose any risk for skin cancers except on male genitals. This risk, however, can be significant (4.5%) at high doses.

Narrowband Ultraviolet B (NB-UVB) Radiation

Narrowband radiation may be safer than other approaches, and some scientists now believe it should be the first option for patients with chronic plaque psoriasis.

NB-UVB is used without medications and is very strong. Whether it has any effect on the disease process itself is unclear. The light wavelength is between 310 - 312 nanometers, which is the most beneficial part of sunlight.

Exposure times are shorter, but of higher intensity than with broadband UVB. This therapy is probably less likely than PUVA to cause skin cancers.

Clearance of 75% typically occurs after 10 - 12 treatments. NB-UVB treatments performed three times a week achieve results that are equal to twice-weekly PUVA treatments. Weekly NB-UVB treatments are not effective. Studies so far are mixed on whether NB-UVB remission rates are equal to those of PUVA.

Patients prefer NB-UVB over other PUVA treatments because they do not have to wear protective eyewear, take medications, or experience unpleasant side effects such as nausea. NB-UVB is also safe for pregnant women and children.

Combinations with topical medications, such as tazarotene or psoralens, may help NB-UVB therapy work more effectively.

Laser Treatments

Laser UVB Treatment. A variation of a device called an excimer laser (Xtrac) delivers a precise UVB wavelength of 308 nanometers. The laser is more effective than narrowband UVB for localized psoriasis, because it allows very specific areas of skin to be targeted. (Note: The therapy is not suitable for the scalp.) Generally, 8 - 10 treatments given twice a week will clear psoriasis. Remission rates are similar to those of NB-UVB, but the excimer laser can clear the psoriasis faster and at lower doses. It also spares the healthy skin around it. Blistering is a common side effect. More comparison studies are needed to determine risks and benefits compared to NB-UVB, particularly any long-term risk for skin cancer.

Pulsed-Dye Lasers. Pulsed-dye lasers give off high-intensity yellow light, which destroys the tiny blood vessels that make up psoriatic plaques. This treatment has been used for years to remove birthmarks, such as port wine stains and unsightly blood vessels on the skin. Some studies have reported significant (but not complete) improvement of psoriasis, and remissions that have lasted up to 13 months. Treatment sessions can take up to 30 minutes and can feel uncomfortable (similar to being repeatedly snapped with a rubber band). It typically takes up to six sessions to clear the target areas. Bruising is common, and there is a small risk for scarring.

Commercial Tanning Units

Home tanning devices and tanning salons are not usually recommended, but they may be helpful for patients who do not have access to a medical facility. Many patients have achieved a significant reduction in symptoms after taking acitretin and being exposed to a UVB commercial tanning unit (specifically, a Wolff tanning bed).

However, UV outputs can vary widely among tanning beds and salons. Some units emit UVA radiation, which poses a higher risk for skin cancers. Adverse effects of tanning salons that use UVA or UVB radiation are the same as with any UV phototherapies, including a risk for skin cancer.

Review Date: 10/21/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).