Does offer benefits for some skin conditions. In a medical setting, the same ultraviolet light that’s emitted from the sun can be carefully used as therapy for certain hard-to-treat skin problems and other medical conditions.

The main forms of ultraviolet light that reaches us from the sun are called ultraviolet A (UVA) and ultraviolet B (UVB). These are the same wavelengths of light that are used for medical therapies.

Ultraviolet light causes changes in cell DNA leading to cell damage and possible cell mutations that can turn a normal skin cell into a cancerous one. UVB rays are those responsible for sunburn. UVA rays penetrate skin more deeply, and it’s increasingly recognized that they also set the stage for skin cancer development. UVA is the predominant type of ultraviolet light that comes from tanning beds.

With ultraviolet light therapy, certain aspects of UV light are harnessed for good. Although it’s not fully known why certain skin conditions may respond to ultraviolet light, slowing the overgrowth of skin cells and altering the immune system are two mechanisms that appear to be at work.

Therapy sessions may last from a few seconds to an hour and may take place two to seven days a week. It may take dozens of sessions before an adequate response is achieved