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Red light therapy refers to the practice of exposing the body to light in the red and near-infrared (NIR) spectrum with the goal of producing health benefits. Red light therapy can be beneficial for hair loss, joint pain, and childhood myopia.
Red Light Therapy is most often used for
Last Updated:October 24, 2023
Red light therapy refers to the practice of exposing the body to red and/or near-infrared light, with the goal of producing health benefits. There is considerable variation in how red light therapy is performed in practice, with differences in factors like the wavelengths of light used, the power intensity (irradiance) of the light, the duration and frequency of exposure, and the regions of the body irradiated.
Red light therapy can reduce pain in a variety of contexts, especially conditions involving joint pain, including knee osteoarthritis,[1] lower back pain,[2] and neck pain.[3] There is also preliminary evidence that red light therapy can reduce pain in fibromyalgia,[4] tendinopathy,[5] rheumatoid arthritis,[6] and headache,[7] as well as during hip surgery recovery.[8]
Red light therapy has been shown to promote hair regrowth in people with hair loss due to androgenic alopecia, with effects seen in both men and women.[9][10] In these studies, the scalp is directly exposed to red light, usually in the 650 to 660 nm range.
Red light therapy has been found to be beneficial for childhood myopia (nearsightedness), slowing its progression and even preventing its occurrence.[11][12][13] Red light therapy may also be helpful for other eye conditions (e.g., macular degeneration, cataracts), but research is still too limited to be certain of its effectiveness.[14][15][16]
Preliminary evidence suggests red light therapy can improve cognitive function in people with dementia[17] and possibly in healthy people as well.[18]
Red light exposure to the eye is risky and can result in damage to the retina.[19] For this reason, red light therapy for eye conditions should only be performed under the guidance of a qualified medical professional.
Eye use excluded, red light therapy appears to be fairly safe, with reported side effects tending to be rare and mild (e.g., itchy skin, acne, and skin tenderness).[9] Red light exposure can also produce a sunburn-like effect if the power intensity and duration of exposure are high enough. Interestingly, individuals with darker skin pigmentation appear more susceptible to this effect (unlike with ultraviolet light exposure, where the opposite is true).[20]
The mechanism by which red light therapy works is not well-established, although most explanations center on its ability to increase cellular energy generation. More specifically, red and near-infrared light are thought to stimulate the activity of the mitochondrial protein cytochrome c oxidase (CCO), which increases ATP production.[21][22] This increase in ATP synthesis can in turn lead to enhanced tissue repair, changes in gene expression, and the generation of cell signaling molecules, all potentially contributing to the biological effects of red light therapy.[21][23]
To discuss the dosages used in red light therapy, some important terms need to be covered:
Power intensity (also called irradiance): The amount of power delivered per square centimeter of body area per second, often expressed as mW/cm2/s (milliwatts per square cm).
Power density: The product of power intensity and duration of exposure, often expressed as J/cm2 (joules per square cm).
Total energy (the “dose”): The product of power density and body area exposed, usually expressed as J (joules).
Red light therapy for eye conditions uses the lowest doses, with most studies using power intensities below 1 mW/cm2 for around 3 minutes per session, corresponding to a power density well below 1 J/cm2. Red light therapy for hair loss typically involves power intensities of around 3–90 mw/cm2 for around 15–20 minutes per session, resulting in a power density of around 1–10 J/cm2. Finally, some research suggests the effective dose for knee osteoarthritis is around 4–8 J per spot for light with a wavelength range of 780–860 nm and around 1–3 J per spot for light with a wavelength of 904 nm.
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This page is brand new! We wrote FAQs for it and added key findings from the latest meta-analyses to the database.