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Light therapy is clearly enjoying a moment. There are now available glowing gadgets designed to address complexion problems and aging signs as well as sore muscles and gum disease, the latest being a toothbrush equipped with small red light diodes, described by its makers as “a significant discovery in personal mouth health.” Internationally, the market was worth $1bn in 2024 and is projected to grow to $1.8bn by 2035. You can even go and sit in an infrared sauna, which use infrared light to warm the body directly, your body is warmed directly by infrared light. According to its devotees, it feels similar to a full-body light therapy session, stimulating skin elasticity, soothing sore muscles, alleviating inflammatory responses and persistent medical issues while protecting against dementia.

Research and Reservations

“It sounds a bit like witchcraft,” notes a neuroscience expert, a scientist who has studied phototherapy extensively. Of course, some of light’s effects on our bodies are well established. Sunlight helps us make vitamin D, essential for skeletal strength, immune function, and muscular health. Light exposure controls our sleep-wake cycles, as well, triggering the release of neurochemicals and hormones while we are awake, and preparing the body for rest as darkness falls. Artificial sun lamps are a common remedy for people with seasonal affective disorder (Sad) to boost low mood in winter. Undoubtedly, light plays a vital role in human health.

Different Light Modalities

While Sad lamps tend to use a mixture of light frequencies from the blue end of the spectrum, the majority of phototherapy tools use red or near-infrared wavelengths. During advanced medical investigations, such as Chazot’s investigations into the effects of infrared on brain cells, determining the precise frequency is essential. Light is a form of electromagnetic radiation, extending from long-wavelength radiation to the highest-energy (gamma waves). Light-based treatment employs mid-spectrum wavelengths, the highest energy of those being invisible ultraviolet, followed by visible light encompassing rainbow colors and finally infrared detectable with special equipment.

UV light has been used by medical dermatologists for many years to treat chronic skin conditions such as eczema, psoriasis and vitiligo. It modulates intracellular immune mechanisms, “and dampens down inflammation,” notes a skin specialist. “Considerable data validates phototherapy.” UVA goes deeper into the skin than UVB, while the LEDs in consumer devices (which generally deliver red, infrared or blue light) “typically have shallower penetration.”

Safety Protocols and Medical Guidance

The side-effects of UVB exposure, like erythema or pigmentation, are well known but in medical devices the light is delivered in a “narrow-band” form – meaning smaller wavelengths – that reduces potential hazards. “Therapy is overseen by qualified practitioners, thus exposure is controlled,” notes the specialist. And crucially, the devices are tuned by qualified personnel, “to guarantee appropriate wavelength emission – different from beauty salons, where it’s a bit unregulated, and wavelength accuracy isn’t verified.”

Home Devices and Scientific Uncertainty

Red and blue light sources, he says, “aren’t really used in the medical sense, though they might benefit some issues.” Red wavelength therapy, proponents claim, improve circulatory function, oxygen utilization and dermal rejuvenation, and stimulate collagen production – a key aspiration in anti-ageing effects. “Studies are available,” says Ho. “Although it’s not strong.” Regardless, with numerous products on the market, “we don’t know whether or not the lights emitted are reflective of the research that has been done. Appropriate exposure periods aren’t established, ideal distance from skin surface, if benefits outweigh potential risks. Many uncertainties remain.”

Treatment Areas and Specialist Views

One of the earliest blue-light products targeted Cutibacterium acnes, a microbe associated with acne. Scientific backing remains inadequate for regular prescription – despite the fact that, says Ho, “it’s frequently employed in beauty centers.” Some of his patients use it as part of their routine, he observes, but if they’re buying a device for home use, “we just tell them to try it carefully and to make sure it has been assessed for safety. If it’s not medically certified, the regulation is a bit grey.”

Cutting-Edge Studies and Biological Processes

Simultaneously, in advanced research areas, researchers have been testing neural cells, revealing various pathways for light-enhanced cell function. “Pretty much everything I did with the light at that particular wavelength was positive and protective,” he says. The numerous reported benefits have generated doubt regarding phototherapy – that claims seem exaggerated. However, scientific investigation has altered his perspective.

Chazot mostly works on developing drug treatments for neurodegenerative diseases, though twenty years earlier, a physician creating light-based cold sore therapy requested his biological knowledge. “He developed equipment for cellular and insect experiments,” he recalls. “I was quite suspicious. It was an unusual wavelength of about 1070 nanometres, that many assumed was biologically inert.”

The advantage it possessed, nevertheless, was that it travelled through water easily, meaning it could penetrate the body more deeply.

Cellular Energy and Neurological Benefits

More evidence was emerging at the time that infrared light targeted the mitochondria in cells. Mitochondria are the powerhouses of cells, generating energy for them to function. “All human cells contain mitochondria, even within brain tissue,” says Chazot, who concentrated on cerebral applications. “It has been shown that in humans this light therapy increases blood flow into the brain, which is always very good.”

With 1070 treatment, mitochondria also produce a small amount of a molecule known as reactive oxygen species. In limited quantities these molecules, explains the expert, “activates protective proteins that safeguard mitochondria, preserve cell function and eliminate damaged proteins.”

These processes show potential for neurological conditions: free radical neutralization, inflammation reduction, and pro-autophagy – autophagy being the process the cell uses to clear unwanted damaging proteins.

Present Investigation Status and Expert Assessments

Upon examining current studies on light therapy for dementia, he reports, about 400 people were taking part in four studies, comprising his early research projects