What is red light therapy?

Red light therapy, which is formally known as photobiomodulation, refers to the use of light to change human biology, including at a cellular level. According to Zakia Rahman, a clinical professor of dermatology at Stanford School of Medicine and faculty member at the Stanford Center on Longevity, both red and infrared light can stimulate energy production inside mitochondria, which can help cells work more effectively.

Although red light therapy has become more well known in recent years, scientists have been studying the effects of red light on biology for decades. In the 1960s, a Hungarian scientist exposed mice to low levels of red light to see if it would cause them to develop skin cancer. Instead, the mice exposed to red- light grew more hair, leading to additional studies in both mice and humans.

Since then, there have been several studies on red light and its effects on several health conditions, including hair growth, skin rejuvenation, wound healing, and more. On social media, content creators have also claimed that it can help with joint pain, sleep, ADHD, and longevity.

"If you invest in a red light therapy panel to have at home, your holistic wellness routine just got elevated," said Kristina Elise, a wellness influencer on TikTok.

As interest in red light therapy grows, more devices for the treatment are appearing in dermatology offices, wellness centers, locker rooms, and homes. According to some projections, the global market for red light devices could exceed $1 billion by 2030.

Uses of red light therapy

Although interest in red light therapy is high, Rahman said that it can be difficult to distinguish science from hype when it comes to treatment. Currently, there are several potential uses of red light therapy, although the evidence for each varies.

Hair growth and skin care

Research has shown that red light penetrates the skin at shallow depths and stimulates follicle growth. There is also evidence that red light can cause vasodilation, or the widening of blood vessels.

"We know some hair products, such as topical minoxidil, harness that to stimulate hair growth," Rahman said. "The dilation of blood vessels enables more blood and nutrients to reach the hair follicles."

Red light therapy "does help," said David Ozog, a researcher and chair of dermatology at Henry Ford Health. "You can objectively look at the hairs, the quality of the hairs, the number of hairs, and they improve."

However, red light therapy needs to be used consistently over several months to have an effect on hair growth. The benefits will also depend on several factors, including how much hair you've already lost.

Wound healing and scarring

Some preliminary studies suggest that red light therapy could help accelerate skin and tissue healing, depending on the wavelength of light, duration, and frequency of treatment. However, studies have so far not shown strong and consistent benefits from the treatment.

For example, two studies on the effect of red light therapy on healing from blepharoplasty, or a surgical eyelid lift, resulted in different results. In one study, the red light treatment group did better, but it was not statistically significant. In the other study, the scar treated with red light healed in half the time compared to the nontreated side. However, there was no difference in healing at six weeks.

"It does suggest that in the first few weeks during the first phases of wound healing there could be benefit for red light," said Nour Kibbi, a clinical assistant professor of dermatology at Stanford School of Medicine. "It's very interesting and deserves further study, but for now, the data is somewhat conflicting and there are a lot of caveats." 

Athletic performance, sleep, and more

Theoretically, red light could be used to stimulate muscle and tissue healing similarly to how it's used for wound healing. However, Jamie Zeitzer, a sleep expert, and Michael Fredericson, a sports physician, said there is limited evidence to support red light therapy for either athletic performance or sleep.

Red light therapy has also been touted as a treatment for erectile dysfunction, chronic pain, and dementia, but none of these treatments have been scientifically validated.

"[I]n some areas we have reached the highest level of evidence" for the health benefits of red light therapy, Arany said. "In other areas, it remains more anecdotal," with promising evidence, but more rigorous studies are needed. 

Potential concerns and limitations of red light therapy

According to Elma Baron, a dermatologist and professor at Case Western Reserve University School of Medicine, "[r]ed light is something that has a pretty high safety margin." However, there are still some potential safety risks people should be aware of.

If you're using red light therapy, it's important to protect your eyes since prolonged exposure can damage your retina. "It's possible you could cause some harm," Ozog said.

Other potential risks of red light therapy include headaches and melasma, a form of hyperpigmentation that is more common among people of color. Although longer wavelengths of red light are less likely to stimulate pigmentation, there is still some risk. "[O]verusing it can absolutely cause people with pigment disorders to actually worsen," Rahman said.

Health experts also say consumers should be careful about the type of red light therapy devices they buy. Currently, there are red light face masks, wands, and special caps for hair growth sold for at-home use, but it's not clear whether these devices provide any benefits.

"[T]he buyer beware advice is it's a little bit like the Wild West," Ozog said. Although many red light devices being sold have been cleared by FDA, this just means they are safe but not necessarily effective. Because treatment isn't one-size-fits-all, different wavelengths are needed to be effective to treat different health conditions. The optimal wavelength for skin rejuvenation is not necessarily the same for hair growth.

If you are interested in buying a red light device, Ozog recommends looking for "independent safety certification from a recognized lab such as Intertek or UL [Solutions], plus separate third-party optical testing for wavelength and irradiance."