Everybody reacts differently, with most people requiring UV phototherapy two to four times per week.

Phototherapy and psoriasis

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

UV phototherapy affects skin cell growth and the immune cells involved in psoriasis. UV phototherapy treatment involves entering a special light box and exposing all affected areas to UV rays for a specific period of time.

There are currently two types of UV phototherapy treatments that are commonly used.

UVB phototherapy treatment

Ultraviolet B (UVB) therapy is generally recommended for people with psoriasis who have plaques that cover significant areas of their body, making topical treatment difficult. Most people will receive two to three UV phototherapy treatments per week. Dosages are determined by the dermatologist and tailored to the individual. Your dermatologist may recommend combining UVB treatments with topical or systemic treatments to improve their effectiveness, speed up results, and/or limit side effects by decreasing the number of treatments and the dosages of the medications.

Narrowband UVB

Narrowband phototherapy, a form of UVB therapy, uses a narrower spectrum of light than broadband UVB.

PUVA phototherapy treatment (pronounced "poova")

PUVA (psoralen ultraviolet A) combines UVA exposure with a photosensitizing agent that is taken internally in pill form or topically in a bath solution.

UVA phototherapy treatment is usually administered when psoralen levels in the skin are high. Depending on the type of oral PUVA, patients are instructed to take the psoralen pills from 1 to 3 hours before going inside the UVA light box. The amount of time spent under the lights depends on skin type (the darker or more tan you are, the more time it will take). Approximately 20-25 phototherapy treatments are needed to see clearing.

Other important information you should know

All medicines have potential side effects and should be used cautiously and under the supervision of a healthcare professional. Some common adverse events associated with UV phototherapy include skin irritation, light sensitivity, and burning.