LED panels, masks and caps that shine red and near-infrared light on skin. Modest evidence for hair loss and fine lines; weak for whole-body claims.
Red-light therapy, properly called photobiomodulation (PBM), shines low-power red (about 630–680 nm) and near-infrared (about 800–880 nm) light onto the body. It isn't meant to heat you like a sauna or set your body clock like a light box. The claim is that the light acts on the cells it reaches, mainly through a light-absorbing enzyme in mitochondria.
The category spans full-body panels, face masks, laser and LED hair caps, handheld wands, belts and blankets. Red light is absorbed mostly in the skin and near-infrared a little deeper, so the more targeted the claim (scalp, face, a mouth sore), the more plausible it is.
It depends entirely on the use. Sham-controlled trials show modest gains in hair density for pattern hair loss, and controlled trials report smoother skin and fewer fine lines, though many studies are small or industry-linked. Clinician-delivered PBM is guideline-recommended to prevent mouth sores during some cancer treatments. For whole-body claims (testosterone, fat loss, thyroid, immunity, longevity) there is little or no good human evidence, and dose matters: too little light does nothing, and too much can cancel the effect.
Across four sham-controlled trials in 269 men and women with pattern hair loss, three home sessions a week for 26 weeks increased terminal hair counts by about 18–26 hairs/cm², versus about 2–9 with sham devices. No serious adverse events.
In 136 volunteers, twice-weekly red or broad-spectrum light for 30 sessions improved skin roughness, collagen density on ultrasound and blinded photo ratings compared with untreated controls; the broader spectrum was no better than red light alone.
The MASCC/ISOO mucositis group recommends specific photobiomodulation protocols to prevent oral mucositis in stem-cell transplant and head-and-neck radiotherapy patients, but found too little evidence to recommend it for treating established mucositis.
Reviews cell, animal and clinical work showing that low doses of red and near-infrared light often work better than higher doses, and that inconsistent choices of wavelength, dose and timing explain many conflicting trial results.