PDT is popularly used in treating acne. It is used clinically to treat a wide range of medical conditions, including wet age-related macular degeneration, psoriasis, atherosclerosis and has shown some efficacy in anti-viral treatments, including herpes. It also treats malignant cancers including head and neck, lung, bladder and particular skin. The technology has also been tested for treatment of prostate cancer, both in a dog model and in human prostate cancer patients.

It is recognised as a treatment strategy that is both minimally invasive and minimally toxic. Other light-based and laser therapies such as laser wound healing and rejuvenation, or intense pulsed light hair removal do not require a photosensitizer. Photosensitisers have been employed to sterilise blood plasma and water in order to remove blood-borne viruses and microbes and have been considered for agricultural uses, including herbicides and insecticides.[citation needed]

Photodynamic therapy's advantages lessen the need for delicate surgery and lengthy recuperation and minimal formation of scar tissue and disfigurement. A side effect is the associated photosensitisation of skin tissue. Photodynamic therapy (PDT) is a treatment that uses a drug, called a photosensitizer or photosensitizing agent, and a particular type of light. When photosensitizers are exposed to a specific wavelength of light, they produce a form of oxygen that kills nearby cells (1–3).Each photosensitizer is activated by light of a specific wavelength (3, 4). This wavelength determines how far the light can travel into the body (3, 5). Thus, doctors use specific photosensitizers and wavelengths of light to treat different areas of the body with PDT. Photodynamic therapy (PDT) is a treatment that uses special drugs, sometimes called photosensitizing agents, along with light to kill cancer cells. The drugs only work after they have been activated or “turned on” by certain kinds of light. PDT may also be called photoradiation therapy, phototherapy, or photochemotherapy.Depending on the part of the body being treated, the photosensitizing agent is either put into the bloodstream through a vein or put on the skin. Over a certain amount of time the drug is absorbed by the cancer cells. Then light is applied to the area to be treated. The light causes the drug to react and form a special kind of oxygen molecule that kills the cells. PDT might also help by destroying the blood vessels that feed the cancer cells and by alerting the immune system to attack the cancer.The period of time between when the drug is given and when the light is applied is called the drug-to-light interval. It can be anywhere from a couple of hours to a couple of days, depending on the drug used.

The light used in PDT comes from certain kinds of lasers or from light-emitting diodes (LEDs). The kind of light used depends on the type of cancer and where it is located in the body. PDT is usually done as an outpatient procedure (meaning you won't have to stay in the hospital) but is sometimes combined with surgery, chemotherapy or other anti-cancer drugs, or radiation therapy.