What Is Light Therapy?
Light therapy has become a popular health treatment with health care professionals and individuals at home. So what exactly is light therapy?
Keep reading for a breakdown of light therapy that answers the following questions:
What is light therapy?
How does light therapy work?
What are the health benefits of light therapy and which conditions can light therapy treat?
What colors and wavelengths of light are used for light therapy?
How often should you use light therapy?
Is light therapy safe?
What Is Light Therapy?
Light therapy is a treatment that shines specific wavelengths of light on the body to produce a beneficial effect. Light therapy usually refers to a medical or at-home treatment that uses light emitting diodes (LEDs) to shine wavelengths of red, blue, green, or full-spectrum light on the body. Light therapy may also refer to the use of lamps designed to improve the symptoms of seasonal affective disorder (SAD) by mimicking natural sunlight.
People shine light on their skin and cells because specific wavelengths and colors of light can have a beneficial effect on your health. Some light therapy devices are designed to treat specific concerns, like cold sores or hair loss. These devices tend to be smaller, more portable, and more targeted with their treatment areas (the parts of the body receiving light during a light therapy session).
Larger light therapy devices use panels of LEDs to deliver light to a wider section of the body for more systemic benefits like improved sleep, energy, recovery, and inflammation. Light therapy is also widely used to treat skin conditions like acne and scars.
Light treatments are supported by over 2,000 peer-reviewed clinical studies. This research has shown that light therapy is noninvasive, well-tolerated by patients of all ages, and almost completely free of side effects and complications. [1,2]
Light therapy technology has been used in medicine since the beginning of the 1900s. NASA experimented with red light therapy use in space in the 1980s and 1990s. 
But over the last 20 years, light therapy has become far more popular with the public, thanks to hundreds of affordable consumer light therapy products coming available. These products use the same advanced LED technology to isolate specific wavelengths of light with therapeutic effects.
How Does Light Therapy Work?
Why does the body respond to light therapy?
For starters, every living thing needs light to survive and thrive, from the tiniest plant to the largest mammal. The mitochondria in our cells absorb wavelengths of light from the sun and use it to make energy and power the body with adenosine triphosphate (ATP). [4,5]
When you take in enough healthy light every day, your cells and body can function more efficiently. [4,5] Light therapy devices shine specific wavelengths of light on the body, supplementing natural sunlight and stimulating specific effects like reducing inflammation or helping a canker sore heal.
Light therapy works well for many people because they don’t get enough natural sunlight from their daily environment. Surveys have found that the average American spends over 90% of their time indoors.  If your body and cells aren’t taking in healthy light every day, you can develop chronic problems with physical performance, inflammation, and sleep.
Light therapy treatments with red wavelengths have also been shown to enhance blood circulation, reduce pain, and help the body process inflammation. [7,8]
What Are the Health Benefits of Light Therapy?
Which conditions can you treat with light therapy?
These are some of the most common and effective uses for light therapy treatments:
Light Therapy for Skin and Beauty
Light therapy is most popular as a skin and beauty treatment. Widely used in clinical settings by dermatologists, and in salons and spas by estheticians, light therapy treats skin conditions like cold sores, canker sores, acne, wounds, burns, and genital herpes.
You can learn more about light therapy for skin health on this page. Keep reading for a rundown of the most common skin health benefits of light therapy.
Light Therapy for Cold Sores
Light treatments are used to treat cold sores and outbreaks caused by the herpes simplex virus. Wavelengths of red light are the most effective for reducing the pain of cold sores and improving healing times for outbreaks. One example of a home use light therapy device for cold sores is the Luminance RED Cold Sore Treatment Device.
In 2018, researchers conducted a systematic review of all clinical trials done on cold sores and light therapy. Every study they reviewed showed light therapy “to be effective in the management and prevention of recurrent herpes labialis, without any side effects.” 
Another comprehensive review of trials on cold sores and light therapy concluded, “Phototherapy appears to strongly decrease pain and the interval of recurrences without causing any side effects.” 
Learn more about light therapy for cold sores in this article.
Light Therapy for Canker Sores
Light therapy is used to treat and prevent canker sore outbreaks and improve healing times. More than 25 clinical studies have demonstrated that light therapy significantly reduces pain from canker sores, speeds the healing time of canker sores, and can make eating, drinking, and functioning normally easier during a severe canker sore outbreak.
A 2019 study concluded that patients with recurrent canker sores “showed remarkable improvements in reduction of pain, healing time, and lesion size” after light therapy treatments. 
Other studies have also found that light therapy treatments can significantly reduce the size of canker sores  and provide immediate pain relief.  In another study, 93% of people experienced “complete pain relief” from canker sores directly after light treatments. 
See more details about light therapy for canker sores in this article.
Light Therapy for Acne
Red and blue light are both used to treat acne, acne scars, and outbreaks.  Devices shine visible light in red or blue wavelengths directly on the affected skin with a handheld wand or LED mask. Visible blue light kills bacteria on the skin, helping to reduce acne and heal outbreaks. Red light reduces inflammation and stimulates regrowth and healing of damaged tissues.
Light therapy has been used by dermatologists for over 20 years, and today you can find many at-home consumer light therapy devices specifically for acne. Light therapy treatments for acne are safe, with few side effects. 
CurrentBody is one example of a red light mask for acne treatments. Facialist Angela Caglia sells a mask with red, blue and NIR settings. Handheld devices like ReVive Light Therapy treat acne with blue light therapy.
Light Therapy for Wounds and Burns
Wavelengths of red and near infrared (NIR) light have proven to be the most effective for treating burns, wounds, and scars. Red and NIR light therapy have also shown great results for inflammation reduction, which is crucial for healing wounds and burns.
Clinical studies on light therapy and wound healing have shown that cells exposed to specific wavelengths of red and NIR light produce new blood vessels and tissues at higher rates, leading to better healing outcomes and less pain. [16,17]
Researchers in a 2018 review determined that light therapy with red wavelengths significantly increased tensile strength and wound contraction, leading to faster, more effective wound healing results across the body.  This comprehensive review also concluded that light therapy with red wavelengths is a safe, effective way to treat open and sutured incisions from surgeries and operations. 
Light Therapy for Genital Herpes
Light treatments with red wavelengths are used to treat genital herpes outbreaks caused by the herpes simplex virus. Light treatments have been shown to relieve pain and improve healing outcomes for genital herpes.
Early clinical research has also indicated light treatments may lessen the viral load of HSV-2 present in the body. 
Check out this article to learn more details about light therapy as a genital herpes treatment.
Light Therapy for Inflammation and Pain
Inflammation relief is one of the core benefits of light therapy. In fact, many of the other benefits of light therapy for skin and recovery come from improving the body’s ability to regulate inflammation more efficiently.
Clinical research has shown that people who have a red light therapy treatment before strenuous exercise report less pain and inflammation after workouts.  Red light therapy can also help prevent delayed onset muscle soreness (DOMS). 
Dr. Michael Hamblin of Harvard Medical School is a leading light therapy researcher. In numerous trials, he has demonstrated that wavelengths of red and NIR light help to significantly reduce inflammation. He has shown “an overall reduction in inflammation, which is particularly important for disorders of joints, traumatic injuries, lung disorders and in the brain.” 
Red light therapy has also shown positive results for types of arthritis and joint pain. Studies have found red light therapy can increase hand flexibility while reducing pain, swelling, and morning stiffness caused by arthritis. 
Light Therapy for Hair Loss and Stimulating Hair Growth
A growing base of clinical research is demonstrating that light therapy treatments with red wavelengths can stimulate hair growth, improve hair thickness, and help prevent hair loss in people with male or female pattern baldness. [23,24,25]
Red light therapy has been shown to have a major stimulating effect on dermal papilla cells, which play a big role in the regulation of hair cycling and growth.  When comparing red light therapy to other common alopecia treatments such as hormone-regulating drugs like Finasteride and Dutasteride, researchers concluded that red light therapy was the superior treatment. And because red light therapy had no negative side effects, patient satisfaction was very high. 
Today, consumers can find many light therapy products designed specifically for stimulating hair growth and preventing hair loss. Designs vary widely, from caps like CapillusPro, to combs and brushes with LEDs, to bands like the HairMax LaserBand 82.
Light Therapy for SAD and Seasonal Depression
One of the most popular uses for light treatments is for SAD, or seasonal affective disorder. Seasonal depression or “winter blues” affects as much as 5% of the population. 
Many people use a SAD lamp that shines bright light or white light into the home to mimic sunlight and lessen the sense of darkness that comes in the winter months. Verilux HappyLamp is one leading example of a bright light lamp used for SAD.
These treatments for SAD symptoms affect light levels in the home, but they are not designed to have a biological effect in human cells like the other forms of red, blue, and NIR light therapy discussed above. However, recent research may indicate that wavelengths of near infrared (NIR) light have a therapeutic effect on the brain and improve the course of mental illness.
In 2018, leading mental health researchers conducted the Elated-2 Pilot Trial to test transcranial NIR light therapy for people with major depression symptoms. This groundbreaking study’s positive findings encourage optimism about wider use of natural light treatments for people with depression. 
Light Therapy for Sleeping Better and Regulating Circadian Rhythm
The body and brain rely on cues from natural light to regulate circadian rhythm and produce sleep hormones like melatonin. 
Many people struggle to sleep because they don’t get enough natural light during the day and overload their eyes and brains with bright artificial blue light from screens at night. This throws off hormone production and the sleep cycle, and can lead to sleep disorders like insomnia.
Clinical research is showing that exposure to red light therapy can improve sleep quality and duration, and help people produce more of their own melatonin. 
Red light has a much lower color temperature than blue light or sunlight, so it’s a good choice for winding down in the evenings and transitioning into restful sleep.  Research has also shown that red light doesn’t upset your sleep cycle like bright blue light can. 
Joovv is an example of a red and NIR light therapy brand that makes full-body devices with sleep settings designed to shine less intense red light for evening use.
Colors and Wavelengths Used for Light Therapy
Which colors are best for light therapy benefits?
Sunshine is full-spectrum light, meaning rays of sunshine contain all wavelengths of light. Light therapy devices isolate the specific wavelengths and colors that have the most benefit for human cells.
To date, red light is the most common color used for light therapy. Near infrared light therapy is also popular, often in conjunction with red light. [7,32]
Red light has wavelengths in the 620 to 750 nanometer range. This narrow band of the electromagnetic spectrum has shown great clinical results for skin, inflammation, pain, healing, and energy production, with few side effects.
Blue light therapy, using wavelengths in the 450 to 490 nanometer range, has been mostly used for acne treatments, or to brighten electronics. [33,34,35,36]
Other light therapy colors, like orange, yellow, and green light, are only beginning to be studied in depth in clinical settings. [33,34,35,36]
Green light therapy in the 495 to 570 nanometer range has shown early positive results related to migraines in select clinical studies. 
Learn more about different colors and wavelengths of light therapy on this page.
How Often Should You Use Light Therapy?
Different devices have varying recommendations about frequency of use, but for the best results, you should generally do your light therapy treatments every day, or at least five times per week.
Consistency is crucial for effective light therapy. The more regularly you use light therapy, the better your results will be. One treatment may produce a short-term benefit, but regular light therapy is needed for longer-lasting effects.
For people treating skin conditions, do two to three short light therapy sessions per day as soon as you feel symptoms emerging. You can go to spas, salons, or physicians for light therapy treatments, but using a personal light therapy device at home is best if you can. Light therapy at home is more effective because it’s easier to do every day, and it costs far less than regular trips to the salon.
Check out this post for more details on how often you should use light therapy.
Risks and Side Effects of Light Therapy Treatments
Is light therapy safe?
Yes, light therapy has been tested and analyzed in thousands of peer-reviewed trials. The consensus among medical researchers and the clinical community is that natural light treatments are safe, well-tolerated, and produce little to no side effects. Research teams have concluded this in study after study. Dermatology researchers from Harvard Medical School conducted a review of red light therapy in 2013 and praised its “noninvasive nature and almost complete absence of side effects.” 
Light therapy is generally safe for eyes and skin. Some people with photosensitivity concerns may experience adverse side effects from initial light therapy treatments. Consult a trusted healthcare provider with specific concerns about light therapy risks and negative interactions with specific medications and conditions.
What Is Not Light Therapy?
Light therapy is a catch-all term for various treatments that shine specific wavelengths of light on a person’s body. Light therapy may refer to treatments with different colors and wavelengths of light, like red, near infrared (NIR), blue, green, or full-spectrum light.
Light therapy has also been called phototherapy, photobiomodulation (PBM), red light therapy (RLT), and LED therapy. Today, a consumer can shop for hundreds of different light therapy products, from small personal devices meant to treat specific skin conditions, to large panels of LEDs meant to treat the whole body with wavelengths of light. You can also find hundreds of brands selling lamps for SAD symptoms.
Light therapy is sometimes confused with other health interventions like infrared saunas or tanning beds. Light therapy is different from infrared saunas and traditional saunas in that it doesn’t use heat to produce a biological response.
Light therapy does not tan the skin and does not contain potentially harmful UV rays. Light therapy differs from natural sunlight in that it uses LEDs to deliver specific wavelengths of light rather than full-spectrum light in accompanied by UV rays and heat.
Sources and References:
 Avci P, Gupta A, et al. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. Seminars in Cutaneous Medicine and Surgery. Mar 2013; 32(1): 41-52.
 Healthline. Light Therapy for Acne, What to Expect.
 NASA. LED Lights Used in Plant Growth Experiments for Deep Space Missions.
 Karu T. Primary and Secondary Mechanisms of Action of Visible to Near-IR Radiation on Cells. Journal of Photochemistry Photobiology. 1999 Mar.
 Ferraresi C, Kaippert B, et al. Low-level Laser (Light) Therapy Increases Mitochondrial Membrane Potential and ATP Synthesis in C2C12 Myotubes with a Peak Response at 3-6 h. Photochemistry and Photobiology. 2015 Mar.
 N E Klepeis, W C Nelson, et al. The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants. The Journal of Exposure Analysis and Environmental Epidemiology. 2001 June.
 Hamblin M. “Mechanisms and applications of the anti-inflammatory effects of photobiomodulation.” AIMS Biophys. 2017.
 Huang YY, Chen ACH, Carroll JD, Hamblin MR. Biphasic dose response in low level light therapy. Dose Response. 2009 Sep.
 Al-Maweri SA, Kalakonda B, AlAizari NA, Al-Soneidar WA, Ashraf S, Abdulrab S, Al-Mawri ES. Efficacy of low-level laser therapy in management of recurrent herpes labialis: a systematic review. Lasers Med Sci. 2018 Sep;33(7):1423-1430.
 de Paula Eduardo C, Aranha AC, Simões A, Bello-Silva MS, Ramalho KM, Esteves-Oliveira M, de Freitas PM, Marotti J, Tunér J. Laser treatment of recurrent herpes labialis: a literature review. Lasers Med Sci. 2014 Jul;29(4):1517-29.
 Soliman HA, Mostafaa D. Clinical Evaluation of 660 nm Diode Laser Therapy on the Pain, Size and Functional Disorders of Recurrent Aphthous Stomatitis. Open Access Maced J Med Sci. 2019 May 14;7(9):1516-1522.
 Jijin MJ, Rakaraddi M, Pai J, Jaishankar HP, Krupashankar R, Kavitha AP, Anjana R, Shobha R. Low-level laser therapy versus 5% amlexanox: a comparison of treatment effects in a cohort of patients with minor aphthous ulcers. Oral Surg Oral Med Oral Pathol Oral Radiol. 2016 Mar;121(3):269-73.
 Prasad R S, Pai A. Assessment of immediate pain relief with laser treatment in recurrent aphthous stomatitis. Oral Surg Oral Med Oral Pathol Oral Radiol. 2013 Aug;116(2):189-93. doi: 10.1016/j.oooo.2013.02.011. Epub 2013 Apr 23. PMID: 23622766.
 Aggarwal H, Singh MP, Nahar P, Mathur H, Gv S. Efficacy of low-level laser therapy in treatment of recurrent aphthous ulcers – a sham controlled, split mouth follow up study. J Clin Diagn Res. 2014 Feb;8(2):218-21.
 Healthline. Is light therapy the acne treatment you’ve been looking for?
 Silveira PC, Ferreira KB, et al. Effect of Low-Power Laser (LPL) and Light-Emitting Diode (LED) on Inflammatory Response in Burn Wound Healing. Inflammation. 2016 Aug.
 da Silva Melo, Alves LP, et al. LED phototherapy in full-thickness burns induced by CO2 laser in rats skin. Lasers in Medical Science. 2018 Sep.
 Gál P, Stausholm MB, et al. Should open excisions and sutured incisions be treated differently? A review and meta-analysis of animal wound models following low-level laser therapy. Lasers in Medical Science. 2018 Aug.
 Waked, Deghidi, and Shalaan. HONEY PHONOPHORESIS VERSUS LOW INTENSITY LASER THERAPY IN FEMALE GENITAL HERPES. IJCRR, Vol. 6, Issue 10. May 2014.
 Leal-Junior EC., Lopes-Martins R., et al. “Effects of low-level laser therapy (LLLT) in the development of exercise-induced skeletal muscle fatigue and changes in biochemical markers related to postexercise recovery”. J Orthop Sports Phys Ther. 2010 Aug.
 Douris P., Southard V., Ferrigi R., Grauer J., Katz D., Nascimento C., Podbielski P. “Effect of Phototherapy on delayed onset muscle soreness”. Photomed Laser Surg. 2006 June.
 Brosseau L, Welch V, et al. Low level laser therapy for osteoarthritis and rheumatoid arthritis: a meta-analysis. The Journal of Rheumatology. 2000 Aug.
 Liu KH, Liu D, et al. “Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials.” Lasers in Medical Science. 2019 Aug.
 Gupta AK, Mays RR, et al. “Efficacy of non-surgical treatments for androgenetic alopecia: a systematic review and network meta-analysis.” JEADV. 2018 Dec.
 Afifi L, Maranda EL, et al. “Low-level laser therapy as a treatment for androgenetic alopecia.” Lasers in Surgery and Medicine. 2017 Jan.
 Joo HJ, Jeong KH, et al. Various Wavelengths of Light-Emitting Diode Light Regulate the Proliferation of Human Dermal Papilla Cells and Hair Follicles via Wnt/β-Catenin and the Extracellular Signal-Regulated Kinase Pathways. Annals of Dermatology. 2017 Dec.
 American Psychiatric Association. Seasonal Affective Disorder.
 Cassano P, Petrie SR, et al. Transcranial Photobiomodulation for the Treatment of Major Depressive Disorder. The ELATED-2 Pilot Trial. Photomedicine and Laser Surgery. 2018 October.
 Lirong Z., Phyllis Z. “Circadian Rhythm Sleep Disorders.” Neurologic Clinics. 2012 November.
 Morita T., Tokura H. “Effects of lights of different color temperature on the nocturnal changes in core temperature and melatonin in humans.” Journal of Physiological Anthropology. 1996 September.
 Moore, R. “Suprachiasmatic nucleus in sleep-wake regulation.” Sleep Med. 2007 Dec.
 Avci P, Gupta A, Sadasivam M, Vecchio D, Pam Z, Pam N, Hamblin MR. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. Semin Cutan Med Surg. 2013 Mar.
 Lynch, David K.; Livingston, William Charles (2001). Color and Light in Nature (2nd ed.). Cambridge: Cambridge University Press. p. 231. ISBN 978-0-521-77504-5.
 Elert, Glenn. “The Electromagnetic Spectrum, The Physics Hypertextbook.” Hypertextbook.com.
 Kumar, Narinder. 2008. Comprehensive Physics XII. Laxmi Publications.
 Laufer, Gabriel. 1996. Introduction to Optics and Lasers in Engineering.
 Healthline. Green Light for Migraines: Does This Therapy Work?