Phototherapy: let the light heal!

Light is made up of photons, particles that can interact with cells in the body, increase their renewal, enhance their activity or trigger certain reactions. Photons vibrate at different frequencies that determine the color of the light beam and, to a certain extent, its properties. The use of light in medical protocols is still little known in France but it is the subject of much research at the international level. Scientists most often use non-heating radiation (delivered by lasers, lamps or tiny optical fibers) and no side effects.

5 colors to fight cancer

Photodynamic therapy uses light to destroy tumors. This is the research ground of Serge Mordon, a biophysicist at Inserm. "We inject into the body a photosensitive substance that attaches to the cancer cells," he explains. It is activated in contact with a particular light radiation. It can be red, orange, yellow, green or blue, depending on the substance used. The technique is already practiced in dermatology but it is particularly interesting researchers to treat cancers difficult to access surgery, such as the prostate or glioblastoma, a brain tumor almost impossible to remove. "Photodynamic therapy can target cells to destroy by preserving healthy cells," says Serge Mordon.

Green to relieve pain

Migraine often forces those who suffer to lock themselves in the darkness. An Israeli study, published in the journal Brain in 2016, discovered that green light could relieve symptoms, when all other wavelengths worsened them. This research paves the way for devices to help migraine sufferers to come out of their isolation, like glasses allowing only green wavelengths to pass. Other clinical studies have shown interest in fibromyalgia-related pain, and recent work published by the University of Arizona (AU) has investigated the effects of green light in relieving neuropathic pain. Common in HIV, they are also present in other chronic conditions. "I am always surprised to find that the pain of our patients is reduced by an average of 60%," enthuses Mohab Ibrahim, professor in the departments of Anesthesiology and Pharmacology of the AU. By acting synergistically with opioid drugs, green light may reduce the dosage and associated risks of dependence.

Red to heal after surgery

The healing effects of red light are known to relieve the skin after some care in dermatology. But it could also be of great interest in surgery, to reduce postoperative consequences, to speed up the repair of a muscle tear or even after a dental procedure. "Hundreds of clinical studies have been done in many countries," says Dr. Luc Bénichou, a specialist in phototherapy, in his book Treat, Relieve, Beautify with Light (eds JC Lattès). Significant improvements and cures have been achieved in shorter timeframes than usual treatments. The red light is sometimes called "anti-inflammatory". In fact, it induces a faster inflammatory phase, with a proliferation of immune cells, then a longer restorative phase. There is also some work on its benefits on wounds that are difficult to heal, such as leg ulcers or pressure ulcers. If it does not replace traditional care, it would give them a boost.

Purple to stop smoking

A team of American and French research institutes, including Inserm and CNRS, worked on cigarette addiction. The exposure of the participants to violet light made it possible to control the nicotine receptors located inside the brain. Researchers have hung a chemical "nano switch" under the effect of violet light, it folds and prevents nicotine to fix. This blocks the dopamine release mechanism that characterizes the addiction.

Dependence, healing, cancer treatment ... the possibilities offered by phototherapy are gradually emerging from the shadows and shed new light on the medical arsenal. To be continued.

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