Psoriasis is a noncontagious, genetic disease of the immune system, which affects the skin and/or joints. According to the National Institutes of Health, as many as 7.5 million Americans have psoriasis. The most common form, plaque psoriasis, results in raised, red lesions covered by silvery white scales. Psoriasis can be limited to a few lesions or can involve moderate to large areas of skin.
Having 3 to 10 percent of the body affected by psoriasis is generally considered to be a moderate case. More than 10 percent is considered severe. For most individuals, the palm of the hand is about the same as 1 percent of the skin surface. However, the severity of psoriasis can also be measured by how psoriasis affects a person’s quality of life. Psoriasis can have a serious impact even if it involves a small area, such as the palms of the hands or soles of the feet.
From 10 to 30 percent of individuals with psoriasis also develop psoriatic arthritis, which causes pain, stiffness and swelling in and around the joints.
Present in natural sunlight, ultraviolet light B (UVB) is an effective treatment for psoriasis. UVB penetrates the skin and slows the rapid growth of skin cells associated with psoriasis. Treatment involves exposing the skin to an artificial UVB light source for a set length of time on a regular schedule. This treatment can be taken in a medical setting or at home using a unit purchased with a doctor’s prescription. See page 8 to learn more about home phototherapy.
There are two types of UVB treatment, broad band and narrow band. The major difference between them is that narrow-band UVB light bulbs release a smaller range of ultraviolet light.
Narrow-band UVB is similar to broadband UVB in many ways and is becoming more widely used. Several studies indicate that narrow-band UVB clears psoriasis faster and produces longer remissions than broadband UVB. It also may be effective with fewer treatments per week than broad-band UVB. Narrow-band UVB is emerging as an alternative to PUVA therapy, which uses the light-sensitizing medication psoralen plus exposure to UVA light. (See page 11 to learn more about PUVA.) Although not as effective as PUVA, narrow-band UVB is easier for people to undergo and may be safer over the long term.
Both adults and children can benefit from UVB treatment. It is effective in treating psoriasis for at least two-thirds of patients who meet these conditions:
A treatment program may include medicines applied to the skin or taken by mouth, as well as UVB. Topical medicines, such as anthralin, coal tar, calcipotriene (brand name Dovonex) and tazarotene (brand name Tazorac) are effective along with UVB in some people. Using systemic drugs such as methotrexate, biologics and acitretin (brand name Soriatane) with UVB may also improve the effectiveness of the treatment.
Usually, the patient undresses to expose all affected areas to the ultraviolet light. He or she then stands in a treatment booth lined with UVB lamps. Some doctors also have small units for treating areas such as the palms and soles.
A person will generally receive treatments three times per week. It takes an average of 30 treatments to reach maximum improvement of psoriasis lesions. The first exposure to the light is usually quite short, lasting as little as a few seconds. Exposure time depends on the person’s skin type and the intensity of the light emitted from the bulbs.
Since people with lighter skin absorb more light (and sunburn more easily), they start with shorter exposure times than people with darker skin. If there is no itching and/ or tenderness from the previous session, the next treatment will be longer. Administering UVB light is not an exact science. Each person’s reaction to the light is not completely predictable.
UVB requires a significant time commitment. Individuals get the best results when they receive the regular follow-up treatments and strictly adhere to the action plan they make with their doctor.
Once the skin clears, phototherapy may be stopped. Individuals may resume phototherapy to maintain skin clarity as the lesions begin to reappear.
However, studies show that continued UVB treatments after the skin clears can increase remission time. Most people need about eight maintenance treatments per month to prolong periods of skin clarity. However, it is different for every person.
If psoriasis lesions return, an individual may return to three treatments per week. Sometimes rotating different psoriasis treatments can give the skin a break from UVB. This minimizes longterm exposure and possible side effects.
Treating psoriasis with a UVB light unit at home can be an economical and convenient choice. Like phototherapy in a clinic, it requires a very consistent treatment schedule. Individuals are treated initially at a medical facility. Later, they begin using a light booth at home. However, all phototherapy requires a prescription.
A dermatologist experienced in home phototherapy provides instructions on the schedule a person should follow. The length of exposure to ultraviolet light depends on skin type, the type of UVB device and the intensity of light emitted from the home UVB lamps.
Just as with office-based phototherapy, people should take care to protect their eyes and other sensitive areas. Protective eyewear must be worn to protect the eyes from permanent damage. Men should also shield their genitals with clothing or sunscreen. A doctor can provide guidance in this situation.
The most important rule in using home phototherapy is to follow a doctor’s instructions. Even though the treatment is at home, continue with regular check-ups. Home phototherapy is a medical treatment that requires monitoring by a medical professional.