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Phototherapy is certainly having a moment. There are now available illuminated devices designed to address complexion problems and aging signs to muscle pain and gum disease, recently introduced is an oral care tool outfitted with miniature red light sources, marketed by the company as “a breakthrough in personal mouth health.” Globally, 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, where instead of hot coals (real or electric) heating the air, your body is warmed directly by infrared light. Based on supporter testimonials, it feels similar to a full-body light therapy session, enhancing collagen production, relaxing muscles, alleviating inflammatory responses and persistent medical issues as well as supporting brain health.

The Science and Skepticism

“It feels almost magical,” observes a Durham University professor, who has researched light therapy for two decades. Certainly, some of light’s effects on our bodies are well established. Sunlight enables vitamin D production, essential for skeletal strength, immune function, and muscular health. Sunlight regulates our circadian rhythms, too, triggering the release of neurochemicals and hormones while we are awake, and winding down bodily functions for sleep as it fades into night. Sunlight-imitating lamps are standard treatment for winter mood disorders to boost low mood in winter. Undoubtedly, light plays a vital role in human health.

Various Phototherapy Approaches

Whereas seasonal affective disorder devices typically employ blue-range light, the majority of phototherapy tools use red or near-infrared wavelengths. In rigorous scientific studies, including research on infrared’s impact on neural cells, identifying the optimal wavelength is crucial. Light constitutes electromagnetic energy, which runs the spectrum from the lowest-energy, longest wavelengths (radio waves) to short-wavelength gamma rays. Light-based treatment uses wavelengths around the middle of this spectrum, including invisible ultraviolet radiation, then visible light (all the colours we see in a rainbow) and infrared light visible through night vision technology.

Dermatologists have utilized UV therapy for extensive periods to manage persistent skin disorders including eczema and psoriasis. It modulates intracellular immune mechanisms, “and reduces inflammatory processes,” says a dermatology expert. “There’s lots of evidence for phototherapy.” UVA goes deeper into the skin than UVB, whereas the LEDs we see on consumer light-therapy devices (which generally deliver red, infrared or blue light) “typically have shallower penetration.”

Risk Assessment and Professional Supervision

UVB radiation effects, such as burning or tanning, are well known but in medical devices the light is delivered in a “narrow-band” form – indicating limited wavelength spectrum – which minimises the risks. “Treatment is monitored by medical staff, thus exposure is controlled,” explains the dermatologist. Essentially, the light sources are adjusted by technical experts, “to ensure that the wavelength that’s being delivered is fit for purpose – unlike in tanning salons, where regulations may be lax, and wavelength accuracy isn’t verified.”

Consumer Devices and Evidence Gaps

Red and blue LEDs, he says, “aren’t typically employed clinically, but they may help with certain conditions.” Red wavelength therapy, proponents claim, help boost blood circulation, oxygen uptake and cell renewal in the skin, and activate collagen formation – an important goal for anti-aging. “Research exists,” states the dermatologist. “However, it’s limited.” Nevertheless, amid the sea of devices now available, “it’s unclear if device outputs match study parameters. Optimal treatment times are unknown, proper positioning requirements, whether or not that will increase the risk versus the benefit. Numerous concerns persist.”

Specific Applications and Professional Perspectives

Initial blue-light devices addressed acne bacteria, microorganisms connected to breakouts. Scientific backing remains inadequate for regular prescription – even though, notes the dermatologist, “it’s commonly used in cosmetic clinics.” Individuals include it in their skincare practices, he observes, but if they’re buying a device for home use, “we recommend careful testing and security confirmation. Without proper medical classification, the regulation is a bit grey.”

Innovative Investigations and Molecular Effects

Meanwhile, in a far-flung field of pioneering medical science, Chazot has been experimenting with brain cells, revealing various pathways for light-enhanced cell function. “Nearly every test with precise light frequencies demonstrated advantageous outcomes,” he says. It is partly these many and varied positive effects on cellular health that have driven skepticism about light therapy – that claims seem exaggerated. Yet, experimental evidence has transformed his viewpoint.

The researcher primarily focuses on pharmaceutical solutions for brain disorders, but over 20 years ago, a doctor developing photonic antiviral treatment consulted his scientific background. “He created some devices so that we could work with them with cells and with fruit flies,” he says. “I was quite suspicious. It was an unusual wavelength of about 1070 nanometres, that many assumed was biologically inert.”

What it did have going for it, however, was that it travelled through water easily, enabling deeper tissue penetration.

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, creating power for cellular operations. “Mitochondria exist throughout the body, even within brain tissue,” says Chazot, who prioritized neurological investigations. “It has been shown that in humans this light therapy increases blood flow into the brain, which is always very good.”

With specific frequency application, energy organelles generate minimal reactive oxygen compounds. In low doses this substance, notes the scientist, “triggers guardian proteins that maintain organelle health, protect cellular integrity and manage defective proteins.”

These processes show potential for neurological conditions: antioxidant, anti-inflammatory, and waste removal – 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 says, several hundred individuals participated in various investigations, comprising his early research projects