Red light therapy regrows hair

In adults with pattern hair loss, the common inherited thinning at the crown or along the hairline, trials comparing red or near-infrared laser and LED devices with look-alike fake devices mostly found more hairs in a measured patch of scalp after 4 to 26 weeks. A 2025 pooled analysis of 38 studies and 3,098 people found greater gains in hair density with light than with sham, but the size of the effect varied widely between studies. For other kinds of hair loss, including patchy hair loss (alopecia areata), sudden shedding, scarring hair loss and hair loss after chemotherapy, there were too few studies to pool, and the trials did not test whether the result carries over to them. Which kind of hair loss a person has is something a clinician establishes; the trials enrolled people already diagnosed with pattern hair loss.

Hair counts rose more clearly than people's own ratings did. In the largest set of trials, 269 men and women using a laser comb three times a week gained about 18 to 26 hairs per square centimetre over 26 weeks, against about 2 to 9 with a fake comb, yet a Cochrane review of the two trials in women found they did not rate the comb as working better than the fake one. Most device trials were sponsored, funded or partly written by device makers. Whether adding light to minoxidil does more than minoxidil alone is unsettled: two 2025 reviews came to opposite answers. Reports sent to the US FDA describe scalp pain, burns and headaches, and devices overheating; they record that problems were reported, not that the devices caused them.

In a 2025 trial of an LED cap, 160 adults were randomized to red light, blue light, both, or a fake cap for 10 minutes a day. None of the three real caps beat the fake one on the main measure at 16 weeks; combining all three gave 28.5 more hairs per square centimetre than sham. More than half the participants were left out of that analysis, and the trial was registered on a public registry after it had finished. On adding light to minoxidil, a review of seven randomized trials found about 6.6 more hairs per square centimetre with the combination, while an earlier review of four of the same trials, with follow-up of 8 to 12 weeks, found no difference.

One trial compared light on its own with minoxidil on its own. In India, 91 men with pattern hair loss were randomly assigned to red LED light from a clinic machine for 10 minutes three times a week, or to 5% minoxidil lotion twice a day, for six months; 75 completed it. Hair density rose in both groups, from about 105 to 130 hairs per square centimetre with light and from about 98 to 135 with minoxidil. The groups did not differ significantly in hair density, in photographs scored by assessors who did not know the treatment, or in the men's own satisfaction, though fewer men in the light group were rated as having excellent regrowth (6 of 37 against 11 of 38). The trial had no untreated or fake-device group and the men knew which treatment they were getting, and finding no significant difference between two groups of fewer than 40 is not the same as showing the two work equally well.

In the US, laser hair combs are regulated as Class II medical devices, and the FDA's classification record describes their use as promoting hair growth in men at a defined stage of pattern hair loss; it lists 112 clearances under that device code. Thirty-four reports sent to the FDA between 2011 and 2026 about hair laser combs, caps and helmets describe scalp pain, tingling, itching, redness and burns, headaches and migraines, and users who said their hair loss got worse; others describe caps and battery packs overheating, melting or smoking. The larger trials reported no serious side effects.

The proposed explanation is that red and near-infrared light is absorbed by an enzyme in mitochondria, the cell's energy-producing structures, raising energy production, and that in hair follicles this nudges resting follicles into their growth phase and keeps them growing longer. That idea rests mainly on cell and animal work, and the review that sets it out states that the exact mechanism in hair is not known.

The trials with a comparison group followed people for up to about six months, and the longest follow-up found, 48 weeks in 68 people, had no comparison group. The trials used specific devices at set wavelengths and schedules, and counted hairs in a small marked area of scalp. They do not show what happens with years of use or with consumer devices of unknown power. The one trial cited here that tested light in place of an established treatment compared it with minoxidil, in men, for six months, using a clinic machine and not a home cap or comb.