Everybody reacts differently, but most people require repetitive UV treatments before they see substantial clearing.

Phototherapy

Ultraviolet (UV) therapy, often referred to as phototherapy or light treatment, is a form of psoriasis treatment that involves exposing the skin to a carefully measured dose of artificial ultraviolet (UV) light. Two types of UV light are typically used: ultraviolet A (UVA) or ultraviolet B (UVB). These procedures are usually done in a dermatologist's office.

It is not known exactly how UV works on the skin, but researchers believe it may slow the abnormal reproduction of skin cells or damage cells so they are not able to grow and function normally. Treatment involves entering a special light box and exposing entire body or smaller units for limited areas (such as hands and feet) to UV rays for a specific period of time. Side effects of UV light therapy include an increased risk of skin cancer, cataracts, freckles, skin aging, sunburn, and irritation.

There are currently three types of UV treatment: broadband UVB, narrowband UVB, and PUVA.

UVB treatment

Ultraviolet B (UVB) therapy is generally recommended for people with psoriasis that are resistant to treatment or for psoriatic lesions that cover large areas of the body, which make topical treatment difficult. Most people will require 3 treatments per week to see results. Dosages are determined by the dermatologist and tailored to the individual. Broadband UVB is a treatment that has been in use for more than 80 years for the treatment of psoriasis and uses bulbs with a broader range of wavelengths. Over time, studies have indicated that the ideal wavelength of light for the treatment of psoriasis is about 311 nm, which lead to the development of special bulbs for what is called narrowband UVB therapy. Your dermatologist may recommend combining UVB treatments with topical or systemic treatments to improve its effectiveness, speed up results, and/or limit side effects by decreasing the number of treatments and the dosages of the medications. Side effects of UVB light therapy include itchiness, redness, irritation, and sunburn.

Narrowband UVB, or laser phototherapy

A form of UVB therapy, narrowband phototherapy utilizes a narrower spectrum of light than broadband UVB. Medical studies have shown it to be more effective, with faster clearing than broadband UVB, but less effective than PUVA. Burns with narrowband UVB can be more severe and longer lasting.

PUVA treatment (pronounced "poova")

PUVA (psoralen ultraviolet A) combines UVA exposure with a photosensitizing agent that is taken internally in pill form, or topically – either as a cream, lotion, or ointment applied directly to the lesions, or in a bath solution. Side effects of PUVA light therapy include nausea, an increased risk of skin cancer, cataracts, freckles, premature skin aging, itchiness, and redness.

Since the timing of exposure to UVA after taking or applying psoralen can have an impact on the effectiveness of treatment, the UVA treatment is administered when psoralen levels in the skin are high. Depending on the type of psoralen, patients are instructed to take the psoralen pills 1 to 2 hours before going inside the UVA light box. The amount of time spent under the lights depends on skin type (the darker or more tanned you are, the more time it will take). An average of 20 to 30 treatments is needed to see clearing. PUVA is commonly administered 2 to 3 times per week until the desired result is achieved.

Indicated primarily for adults with moderate to severe psoriasis, PUVA treatments can be effective. However, long-term treatment produces premature aging and increases the risk of skin cancer in the same way that long term sun exposure does.

Other important information you should know

All medicines have side effects and should be used as directed and under the supervision of a healthcare professional.

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