Phototherapy is a form of medical treatment in which some form of light is used to address a medical issue. You may also hear phototherapy referred to as “light therapy.” Most classically, ultraviolet light is used in phototherapy, although other forms of light may be used as well, depending on the condition which is being treated. Phototherapy has proved useful for a wide range of conditions.

Depending on the patient and the condition, phototherapy may be performed in a doctor's office, or at home. The advantage of going to a doctor's office is that the patient gets access to expensive top of the line phototherapy lamps, and the doctor can precisely control the level of light the patient is exposed to, and the duration. However, people who require regular phototherapy treatments may prefer to purchase a phototherapy lamp or lightbox for use at home.

Skin conditions like psoriasis, eczema, and acne sometimes benefit from phototherapy. Exposure to the light appears to trigger processes in the skin which reduce outbreaks. In acne treatment, for example, phototherapy kills the bacteria which contribute to acne. Typically the phototherapy is combined with other forms of treatment for maximum effectiveness.

Babies born with jaundice are also treated with phototherapy. Jaundice in newborns is caused by a buildup of a pigment called bilirubin. Phototherapy helps the body convert the bilirubin into a form which can be urinated or excreted, allowing the baby's skin to return to a more usual color. Phototherapy for babies is usually conducted in a hospital immediately after birth, with staff keeping an eye on the baby to make sure that he or she is not struggling with other medical problems.

Some sleep labs recommend the use of phototherapy for sleep disorders, including jet lag. Controlled exposure to light can help to retrain the body, especially in environments where nights are extremely long, making it hard for people to rely on levels of light to determine their sleep schedules.

This treatment is also used for Seasonal Affective Disorder (SAD), a form of depression which occurs in the winter, especially in cold regions at extreme latitudes. Regular phototherapy appears to help SAD patients achieve a more balanced mental state, with many patients mounting lightboxes at home so that they can engage in regular sessions. Some people undergo therapy two to three times a day in the peak of winter, when SAD can become very difficult to cope with.