phototherapy

Phototherapy is the medical use of light to treat a range of conditions by exposing body tissues to specific wavelengths, intensities, and durations. It encompasses visible-light therapies for mood disorders and ultraviolet or visible light for skin diseases, neonatal jaundice, and some cancers, delivered with specialized devices and safety protocols.

In newborns with high bilirubin, blue-light phototherapy converts bilirubin to water-soluble isomers that are more easily excreted. Devices emit blue light in the approximately 460–490 nm range, with eye protection and skin exposure managed by clinicians. Treatment decisions rely on bilirubin levels, age, and overall risk.

Dermatologic phototherapy uses ultraviolet light. Narrowband UVB, around 311 nm, treats psoriasis, eczema, and vitiligo; UVA combined with a photosensitizing agent (PUVA) is another option. Benefits must be weighed against risks such as sunburn, photoaging, and potential skin cancer with long-term use; regimens are supervised by specialists.

Photodynamic therapy employs a photosensitizer that accumulates in target tissues and is activated by light to generate reactive oxygen species that destroy abnormal cells. It is used for selected skin cancers, precancerous lesions, and certain internal tumors, with selective tissue effect and specific wavelengths.

Light therapy for mood disorders, especially seasonal affective disorder, uses bright visible light (commonly 5,000–10,000 lux) for about 20–60 minutes daily. It can improve mood and circadian regulation; safety considerations include eyes, retina, and bipolar disorder risk when misused.

Overall, phototherapy requires clinical guidance and individualized regimens to balance efficacy and safety, and to monitor for adverse effects.