When patients have psoriasis symptoms that do not respond to topical medications alone or have lesions that are too extensive for topical treatment, phototherapy becomes an option. During phototherapy, the patients skin or just the lesions are exposed to ultraviolet lights. Patients usually receive phototherapy treatment in a dermatologist office or psoriasis clinic. There are several types of phototherapy programs available, all with their own advantages and disadvantages.
The excimer laser is effective in treating limited plaque psoriasis and offers two distinct advantages over other forms of phototherapy. Dermatologists are able to target the laser to treat only the psoriatic lesion, which eliminates possible damage to surrounding unaffected skin. Since the lesions are the only thing treated, significantly higher doses of light can be used. Higher doses allow for fewer treatment sessions.
The excimer laser delivers high intensity wavelengths of UVB to the targets psoriasis plaques. Each treatment session lasts only a few minutes and are usually given twice a week. Eight to ten sessions are needed to achieve near clearance. Psoriasis sufferers considering laser treatment should know that many states do not distinguish who can and cannot perform procedures using laser and light sources. Skin treatments using lasers may carry potential side effects and should be performed by a board certified dermatologist or under direct physician supervision.
Also known as photo chemotherapy, PUVA is effective with patients suffering with plaque, guttate and palmar-plantar psoriasis. It offers long lasting clearance to many who respond to the treatment and requires the patient to ingest, topically apply, or bathe in medication called psoralen before being exposed to UVA rays.
Psoralen makes the skin more sensitive to UVA rays which requires the patient to wear UVA blocking sunglasses for the rest of the day when exposed to sunlight because psoralen remains in the eyes for a while. Twenty five treatments spaced between 2 to 3 months are needed before clearing occurs, but due to the inconvenience and side effects, PUVA is usually reserved for patients whose psoriasis has not responded to other treatments or have widespread lesions.
UVB for Psoriasis
UVB phototherapy is highly effective in patients who have moderate to severe psoriasis and thin plaques. Patients usually receive between 2 and 5 treatments per week. During treatment the skin is exposed to UVB, which is generated from a special lamp or laser. To enhance the penetration of UVB rays, an emollient is applied before exposure. There are two types of UVB phototherapy, including broadband which is required 3 to 5 treatments per week.
This UVB therapy has been around for more than 80 years and is highly effective. The broadband light, however, does not reach the scalp and areas where skin folds occur. The new form of UVB therapy is called narrowband because it emits a narrower band of UVB wavelengths. Narrowband UVB therapy is proving to be more effective than the traditional broadband therapy. This form of therapy does have the potential to produce severe burning or if it poses a long term risk for development of skin cancer.