Photobiomodulation Therapy: What It Is, How It Works and Where It Is Used

Photobiomodulation therapy is the use of low-power red and near-infrared light, from lasers or LEDs, to support tissue repair and ease pain and inflammation without heating the tissue. It is the scientific name for what most people call red light therapy, and hospitals already use it in cancer care. Below: the name, the mechanism, how it differs from other light treatments, where clinics use it, safety, and home use.

Key takeaways

• The name photobiomodulation therapy was proposed in a 2015 editorial, after a 2014 consensus meeting with 15 international participants. Anders, 2015
• In the US National Library of Medicine's vocabulary, photobiomodulation therapy is listed as another name for low-level light therapy. NLM MeSH
• Across 10 randomised trials with 689 people, low-level laser light cut the risk of severe mouth sores during cancer treatment to 0.37 of the risk without it. NICE, 2018
• A 2018 review of 31 randomised LED trials in dermatology rated the evidence grade B for acne, cold sores and shingles, and fresh wounds. Jagdeo, 2018
• A 2019 review of 22 placebo-controlled trials with 1,063 people found knee arthritis pain 14.23 mm lower on a 100 mm scale with laser light than with placebo. Stausholm, 2019

Is photobiomodulation therapy the same as red light therapy?

Yes, in substance: red light therapy is the everyday name, and photobiomodulation therapy is the scientific umbrella term. The umbrella is wider, because it also covers clinic lasers and other light colours.

The American Academy of Dermatology describes red light therapy as "also called photobiomodulation". AAD Cleveland Clinic lists photobiomodulation alongside cold laser, soft laser and biostimulation as other names. Cleveland Clinic

The 2015 editorial defined it as light therapy using non-ionising light from lasers, LEDs and broadband sources, in the visible and infrared range. Anders, 2015 It called the process nonthermal, with the light absorbed by molecules already in the body. Our guide to what red light therapy is covers the basics and the history.

Why did low-level laser therapy become photobiomodulation?

Because the old name no longer fitted: nobody had defined "low" or "level", and LEDs and other light sources were now used as well as lasers. Researchers at a joint NAALT and WALT conference in September 2014 judged photobiomodulation the preferred term.

Before that, the same treatment was called low-level laser therapy (LLLT), low-power laser therapy, cold laser, soft laser or biostimulation. The editorial called this "a dismal lack of consistency". Anders, 2015 Photobiomodulation therapy names light alone acting on the body's own molecules, with no added drug.

The US National Library of Medicine agreed to add "photobiomodulation therapy" for its 2016 vocabulary. In that vocabulary, it is an entry term under the heading "Low-Level Light Therapy", next to LLLT and laser biostimulation. NLM MeSH The editorial traces the term in published papers back to 1997.

How does photobiomodulation work inside cells?

The leading explanation is that red and near-infrared light is absorbed in the mitochondria, mainly by an enzyme called cytochrome c oxidase. This is linked to more ATP, the cell's energy molecule, and a chain of signals that calm inflammation.

A 2016 review put it this way: "The leading hypothesis is that the photons dissociate inhibitory nitric oxide from the enzyme". de Freitas, 2016 A second idea is that light opens calcium channels in cell membranes. Downstream, genes linked to cell survival and repair switch on.

A 2017 review notes: "One of the most reproducible effects of PBM is an overall reduction in inflammation". Hamblin, 2017 The effect works in a window of roughly 600 to 1,100 nm, where blood and water absorb least and light travels furthest.

How is photobiomodulation different from photodynamic therapy and UV phototherapy?

Photobiomodulation uses red and near-infrared light alone to support repair. Photodynamic therapy adds a light-sensitive medicine to destroy abnormal cells, and UV phototherapy uses ultraviolet light for skin disease.

	Photobiomodulation	Photodynamic therapy	UV phototherapy
Light	Red and near-infrared, no UV	Lamp or laser	UVB, or UVA with psoralen (PUVA)
Medicine needed	No	Yes: cream, injection or drink	For PUVA: psoralen tablets or soaks
Aim	Support repair, ease pain and inflammation	Damage abnormal cells	Control skin disease such as psoriasis
Typical session	Minutes, per spot or area	10 to 45 minutes	Seconds to minutes, course of 8 to 10 weeks
Known side effects	Mild warmth, tingling or temporary irritation	Burning or stinging; light sensitivity afterwards	Sunburn-like redness, premature skin ageing, raised skin cancer risk

In photodynamic therapy, the medicine is harmless until light activates it, and after an injected or drunk dose, skin or eyes can stay light-sensitive for up to 6 weeks. NHS Its aim of killing cells is the opposite of photobiomodulation. Hamblin, 2018 UV phototherapy figures come from NHS Wales.

The AAD notes that red light has not been linked to cancer, unlike UV. Photobiomodulation is also not heat: the 2015 editorial set it apart from warming tissue with infrared lamps, a difference covered in our red light vs infrared sauna comparison.

What do wavelength, irradiance and J/cm² mean on a photobiomodulation study?

They describe the dose: wavelength is the colour of light, irradiance is its strength on the skin, and J/cm² is the total energy delivered to each square centimetre. Results depend on all three, plus time per spot, number of spots and how often sessions are given.

A 2011 editorial noted that "Correct measurement and reporting of dose remains a major problem". Enwemeka, 2011 Three findings explain why the numbers matter:

• More is not always better: the dose response is biphasic, so too little light does little and far too much can lose the benefit. Huang, 2009
• Strength matters, not only total dose: in rats with arthritis, 3 J/cm² at 5 mW/cm² helped, while the same 3 J/cm² at 50 mW/cm² did not.
• The right dose pays off: in the knee review, trials using the recommended dose per spot found pain 18.71 mm lower than placebo. Stausholm, 2019

Pulsing is still an open question. A review found "no agreement on whether continuous wave or pulsed light is best". Hashmi, 2010 See pulsed vs continuous red light therapy for more, and how much red light therapy is too much for the dose curve.

How is photobiomodulation used for mouth sores during chemotherapy or radiotherapy?

This is its best-established medical use: international cancer guidelines recommend it to prevent oral mucositis, the painful mouth sores caused by some cancer treatments. A trained clinician shines a laser or LED probe inside the mouth, often with points outside it too.

The MASCC/ISOO guideline recommends it for adults having a stem cell transplant with high-dose conditioning, and for head and neck radiotherapy with or without chemotherapy. Zadik, 2019 The 2020 update kept these recommendations, based on 1,197 publications. ASCO Post, 2020

Protocol	Patients	Light	Dose per site	Time per site	Schedule	Where
Zadik, 2019	Stem cell transplant	632.8 nm laser	1.0 J/cm², 18 sites	40 seconds	Daily for 5 days	Inside the mouth
Zadik, 2019	Head and neck radiotherapy	632.8 nm laser	3.0 J/cm², 12 sites	125 seconds	5 days a week, whole course	Inside the mouth
Zadik, 2019	Head and neck chemoradiotherapy	660 nm laser	4.2 J/cm², 72 sites	10 seconds	5 days a week, whole course	Inside the mouth
NICE, 2018	Radiotherapy or chemotherapy	Red or near-infrared probe	Not stated	20 to 30 minutes per session	2 to 5 times a week	Inside, outside or both
Great Ormond Street	Children, around transplant	Handheld red and infrared device	Not stated	About 1 minute per area, 7 to 9 minutes	Daily, about 2 to 3 weeks	Inside the mouth, cheeks, lips, under the chin, throat

NICE found "no major safety concerns" and judged the efficacy evidence adequate. NICE IPG615 Its overview reports one person spared severe mucositis for every 3 treated. The children's data come from GOSH.

These are clinic treatments planned by the cancer team, not something a home device replaces, and no home device should ever go inside the mouth.

Where else do hospitals use photobiomodulation on the skin?

Cancer centres and NHS services use it on the skin for radiation fibrosis, slow-healing wounds, scarring and lymphoedema. A 2023 guideline also lists it for preventing radiotherapy skin reactions in breast cancer.

• Memorial Sloan Kettering: a red LED probe for about 1 minute per area, with sessions from 1 to 15 minutes, for fibrosis, wounds, rashes, scarring and fungal nail infections. MSKCC
• Lymphoedema care: an NHS trust applies red LED light over the skin, one minute per point, 5 to 20 minutes per session, for at least two to three weeks. Dorset County Hospital
• Breast radiotherapy: the MASCC guideline lists photobiomodulation for preventing acute radiation dermatitis, as a consensus recommendation from 42 experts. MASCC, 2023

Do LED panels and masks work as well as clinic lasers for photobiomodulation?

The evidence suggests the light source matters less than the wavelength and dose. A 2018 review concluded that photobiomodulation "is not dependent on lasers or coherence".

The review found about 40 papers comparing lasers and LEDs, and most suggested LEDs could replace lasers without clearly worse results. Heiskanen, 2018 LEDs cost about 100 times less per milliwatt and cover a wider area.

Both are in clinical use: the services above use LEDs, while the mucositis protocols mostly use lasers. Our cold laser vs red light therapy guide compares the two in detail.

Which conditions have the strongest photobiomodulation evidence?

Mouth sores in cancer care have guideline-level support, and neck and knee pain have meta-analyses of clinic laser trials. For LED light on the skin, acne, cold sores and shingles, and fresh wounds have the best support.

• Neck pain: a 2009 Lancet review of 16 trials with 820 people found pain 19.86 mm lower on a 100 mm scale than placebo. Chow, 2009
• Knee arthritis: pain 14.23 mm lower than placebo at the end of treatment, with no adverse events reported. Stausholm, 2019
• Skin: grade B evidence for acne, cold sores and shingles, and acute wound healing, with adverse events rare. Jagdeo, 2018

A 2025 umbrella review of 204 randomised trials found moderate-certainty benefits for several outcomes. Son, 2025 These included disability in knee arthritis, fatigue in fibromyalgia and hair density in pattern hair loss. The authors call it a possible non-invasive add-on.

Is photobiomodulation safe for people with cancer, in pregnancy or on medication?

Clinics use it in cancer care with clear rules: no light near a tumour, care in pregnancy, and a check of all medicines first. At home, anyone with cancer should only use light with their oncology team's agreement.

• Tumours: MSKCC does not shine light near tumours, and the mucositis guideline calls long-term tumour safety "debated". MSKCC
• Pregnancy: MSKCC keeps light off the abdomen, and ASLMS says pregnant women are not good candidates. ASLMS
• Darker skin: the AAD advises seeing a dermatologist first, as visible light can cause dark patches. AAD
• Eyes: the AAD says to wear the recommended eyewear every time, and sunglasses are not a substitute.

Our precautions rule out both devices if you are pregnant, have epilepsy, a thyroid condition or take thyroid medication, or have broken skin on the area. The panel is also not for use while breastfeeding or preparing for pregnancy, after sunburn on the body in the past 2 weeks, or for Fitzpatrick skin types V or VI. Our precautions rule out photosensitising medication, so anyone taking a medicine should check with their pharmacist or doctor before using the device. More in is red light therapy safe.

How do you use photobiomodulation therapy at home on the face and body?

Use the mask for the face and the panel for the body, on clean, intact skin, starting gently and building up. Both are light sources in the photobiomodulation range, used from outside the body.

The 4-Wavelength Red Light Therapy Mask uses VCSEL laser diodes: 72 at 665 nm, 72 at 850 nm and 20 at 1064 nm. It is a full-face shell with one eye opening and no diodes over the eyes.

• Red mode: 665 nm red with 850 and 1064 nm near-infrared, the photobiomodulation mode.
• Blue mode: 460 nm blue with 850 nm near-infrared.
• Start: 50% brightness on the 10-minute timer, stepping up to 70 or 90% only if your skin stays calm.
• Limits: 10-minute sessions up to 4 times a week at high brightness, or 15 minutes up to 3 times a week after three 10-minute sessions the week before, and never more than 20 minutes a day.
• Controls: voice or a handheld controller with a colour screen; it switches off when the timer ends.

The mask covers the face only. For the jawline, under the chin, the neck or the scalp, use the panel.

The 9-Spectrum Red Light Therapy Panel carries LEDs at 480, 590, 630, 660, 670, 810, 830, 850 and 1060 nm, each dimmable from 1 to 100%. Its red and near-infrared channels sit in the photobiomodulation range.

• Position: hang it on a door or wall with the included door hook, pulley, hanging cables and screws, or stand it upright on the floor.
• Distance and time: 10 to 15 minutes per area, about 6 inches for a joint and 12 inches for a broad area, with at least 6 hours between 30-minute sessions.
• Channels: red and near-infrared on, 480 and 590 nm turned down, continuous light.
• Neck and head: side-on or from behind at neck level, goggles on, eyes closed, never aimed straight at the face.

Clinic protocols used small doses at precise points. To stay nearer those gentler ranges, dim each wavelength, set a shorter timer (it starts at 1 minute) or step back from 6 to 12 inches. With either device, keep your eyes closed and never look into the light.

Read the precautions before ordering. Standard shipping to the US, UK and Germany is free. Under our return and refund policy, returns are accepted within 30 days: an unopened device with its seals intact is refunded less a 10% restocking fee, and an opened device that is undamaged and complete is refunded less 20%.

Kivorla devices are general wellness devices, not medical devices, and are not intended to treat or prevent any disease. Clinic photobiomodulation for mouth sores, lymphoedema or radiotherapy skin care is given by trained staff, so if you have cancer or another condition, speak to your care team before using any light device.