Phototherapy involves repeated exposure of the skin to ultraviolet (UV) light to treat various inflammatory skin conditions such as psoriasis, eczema, and vitiligo. This therapy is one of the oldest treatment modalities in dermatology, dating back to the ancient Egyptians, who used natural light in combination with herbal extracts to treat skin disease 1. Phototherapy continues to be a highly preferred treatment by dermatologists . Developments have been made in the past several decades to make phototherapy an effective, convenient, and accessible treatment option for patients.

There are two main types of phototherapy:

• •Ultraviolet B light (UVB), one of the components of sunlight, is especially effective in treating the skin condition. During the treatment patients are exposed to the light for just a few seconds at first, and the exposure time is gradually increased to several minutes per treatment. UVB treatment is sometimes administered with topical treatments such as coal tar, anthralin, or just mineral oil. A form of UVB light known as narrow-band (NB-UVB) has been shown to be even more effective than UVB, and is increasingly being used by dermatologists.
• • Although not as potent as UVB, ultraviolet A light (UVA) is also used in treating the skin condition. UVA treatment generally takes longer than UVB exposure times can reach 15 to 20 minutes but at these higher doses it is also effective in clearing lesions. UVA light is often combined with an oral medication known as psoralen (a treatment known as PUVA).

Patients generally require about 20 phototherapy sessions before they see an improvement in their skin. Although response rates vary, studies suggest that 65% of the patients who receive UVB treatment and 75% of the patients who receive NB-UVB will experience significant skin clearance. Although UVB treatments are more widely used, PUVA may actually be more effective.