What do red light therapy terms mean? A plain-English glossary

Why do the terms matter when you’re comparing devices?

Device listings and articles use a lot of red light therapy terms, from nanometres and mW/cm² to ARTG and RCM. Knowing what each one means makes it easier to compare specifications, read research summaries and check claims. Each entry below gives a short definition and links to the library page that covers the topic in depth.

Before you read on: these definitions are simplified. Research on red light is still developing, and some terms (especially those about how light acts on cells) describe ideas researchers still debate.

This page is general information only, not medical, legal or financial advice.

For skin topics, see red light therapy for skin, what results to expect, rosacea questions and scarring questions.

A

ARPANSA. ARPANSA is Australia’s radiation safety agency. It notes that, unlike some lasers and IPL devices, LED phototherapy used for cosmetic purposes isn’t subject to specific regulation in Australia, and it advises consumers to follow instructions and protect their eyes.[1] See is red light therapy safe?

ARTG (Australian Register of Therapeutic Goods). The ARTG is the TGA’s public register of therapeutic goods that can be lawfully supplied in Australia. Being “included in the ARTG” is market authorisation, meaning permission to supply. It isn’t an endorsement that a product works.[2][3] See TGA and ARTG explained

Australian Consumer Law and consumer guarantees. Under the Australian Consumer Law, products come with consumer guarantees. They must be of acceptable quality, fit for a purpose you told the seller about or that the seller advertised, and match their description. A major failure lets you choose a refund or replacement, or keep the product and get compensation. A minor failure lets the business choose to repair it.[4][5] See buying red light therapy in Australia

B

Biphasic dose response. This is the idea that too little light may produce no measurable effect, and too much may also produce none, or even an inhibitory one. In this sense “dose” includes intensity, session time and how often sessions happen.[6] See how to choose a device

Blue light. Blue light is visible light of roughly 400–500 nm. It doesn’t travel as far into skin as red light.[7] See red light compared with other light and heat

D

Distance from skin. This is how far the device sits from your skin during a session. A device’s stated irradiance only applies at the distance it was measured, so use the distance in your device’s instructions. See how to choose a device

Dose (fluence). Dose, also called fluence or energy density, is how much light energy reaches each square centimetre over a session, in J/cm² (joules per square centimetre). You can estimate it as irradiance in mW/cm² × time in seconds ÷ 1,000.[6] Published figures for skin range from about 4 to 18 J/cm², so dosing isn’t standardised.[8] See how to choose a device

F

FDA cleared vs FDA approved. These are United States terms. Under the FDA’s 510(k) pathway, the FDA can find a device “substantially equivalent” to one already legally on the US market. Premarket approval (PMA) is a separate pathway, the FDA’s most stringent, used for higher-risk devices.[9][10] “FDA approved” is a US term. An FDA decision doesn’t put a product on the ARTG, so it isn’t a substitute for checking the ARTG yourself.[3] See TGA and ARTG explained

I

Infrared sauna. An infrared sauna uses heaters that give off mostly far-infrared energy to warm your body and make you sweat. That’s a different purpose from red or near-infrared light devices.[11] See red light compared with other light and heat

Intended purpose. A device’s intended purpose is what the sponsor says it is for, as recorded in its ARTG entry. Advertising must match that purpose.[12][13] See TGA and ARTG explained

Irradiance (mW/cm²). What is irradiance in red light therapy? It’s the power of the light divided by the area it falls on, sometimes called power density.[6] What does mW/cm2 mean? It stands for milliwatts per square centimetre, the usual unit for irradiance. Published figures for skin range from about 20 to 60 mW/cm².[8] See how to choose a device

L

Laser. A laser produces a narrow, coherent beam of light.[14] Many home devices use LEDs rather than lasers, but some use low-power lasers.[14] See red light therapy myths

LED (light-emitting diode). An LED produces a broader, non-coherent spread of light over a wider area. LEDs and diode lasers are built on the same basic semiconductor principle.[14] Whether lasers and LEDs are equivalent is still debated.[14] See red light therapy myths

Low-level light therapy (LLLT). LLLT is an older name for photobiomodulation, and you’ll still see it in research titles.[8][6] See how red light therapy works

Low-power vs Class 4 laser. “Laser” covers a wide range, from low-power devices to Class 4 cosmetic lasers. In Queensland, Class 4 cosmetic lasers may only be used by licensed operators.[15][16] See red light compared with other light and heat

M

Mask. A mask is a wearable device shaped to sit on or close to the face.[8] A 2026 review noted that most consumer devices for the face are designed as wearable masks.[17] See mask vs panel

Mitochondria and cytochrome c oxidase. Mitochondria are the parts of cells that produce energy (ATP). The most widely discussed theory is that red and near-infrared light act on an enzyme in mitochondria called cytochrome c oxidase.[6] This mechanism is still debated. Some reviews question whether cytochrome c oxidase is the main target.[18][19] See how red light therapy works

Multi-wavelength device. A device that combines more than one wavelength, such as red and near-infrared. Check which wavelengths a device includes in its specifications. See mask vs panel

N

Near-infrared (NIR). Near-infrared light sits just beyond visible red, from about 780 nm, and is invisible. One review gives about 780–1,100 nm and another about 780–2,000 nm.[6][17] The most common NIR wavelengths in devices are about 830–850 nm. For red light vs near infrared, red light is absorbed mostly in the upper layers of skin, while near-infrared reaches deeper tissue.[8] See workout recovery

P

Panel. A panel is a flat light device. Panels range from hand-held units to full-body systems.[8] See mask vs panel

Photobiomodulation (PBM). What is photobiomodulation? It’s the research term for using specific red and near-infrared wavelengths of light to act on cells, particularly their mitochondria. PBM is also known as red light therapy and low-level light therapy, and researchers are still investigating exactly how it works.[8] See how red light therapy works

Photodynamic therapy (PDT). PDT is a prescription clinic procedure that combines a drug with light. It’s not the same as home red light.[20] See red light therapy for skin

R

RCM (Regulatory Compliance Mark). The RCM shows the product is meant to comply with Australian electrical safety rules and links it to a registered Australian or New Zealand supplier.[21] See buying red light therapy in Australia

Red light. Red light is visible light of roughly 600–750 nm. Sources draw the edges slightly differently: one review uses about 600–700 nm and another about 620–750 nm.[6][17] The most common red wavelengths in devices are about 630–660 nm.[8] See how red light therapy works

RLRL (repeated low-level red light). RLRL is a clinical approach, used in research on children’s eyes, in which a specific device shines visible red light into the eye. Optometry Australia describes it as an emerging area and says further longer-term studies are needed.[22] A 2025 laboratory test of one RLRL device measured its light output and estimated that retinal exposure could exceed a US safety standard’s limits, depending on pupil size.[23] It’s very different from home skin devices, which should never be pointed at open eyes. See is red light therapy safe?

S

Sham (in studies). In a study, a sham is a fake or inactive version of the device or procedure being tested, used so researchers can compare results fairly. See mask vs panel

Sponsor. The sponsor is the person or company legally responsible for supplying a therapeutic good in Australia. It’s the sponsor who applies to include the product in the ARTG.[2] See TGA and ARTG explained

T

TGA (Therapeutic Goods Administration). The TGA regulates therapeutic goods, including medical devices, in Australia. Red light products are regulated as medical devices when they’re intended for a therapeutic purpose. Products promoted only for cosmetic or wellbeing purposes, without therapeutic claims, aren’t.[24][25] See TGA and ARTG explained

“TGA approved” vs ARTG inclusion. The TGA says the claim “TGA approved” must not be used in advertising. The accurate description is that a product is included in the ARTG, and that inclusion isn’t an endorsement.[26][2] See TGA and ARTG explained

Therapeutic goods advertising. Advertising for therapeutic goods in Australia must follow the TGA’s legal framework, including the Therapeutic Goods Advertising Code.[12] The Code says advertising must not suggest that a government or government authority has endorsed the goods.[27] See buying red light therapy in Australia

U

UV (ultraviolet). UV is the part of sunlight linked to sunburn and skin damage.[28] Red (about 630–660 nm) and NIR (about 830–850 nm) light fall outside the UV range, which ends at about 400 nm.[8][7] Check the published wavelength range in the device’s specifications. See red light compared with other light and heat

W

Warranty. A manufacturer’s warranty, or an extended warranty you pay for, sits on top of the consumer guarantees and doesn’t replace your consumer guarantee rights.[29] See buying red light therapy in Australia

Wavelength and nanometres (nm). Wavelength describes the colour or type of light. It’s measured in nanometres (nm). Different wavelengths behave differently in skin.[6][8] See how to choose a device

FAQ

What is the difference between red light vs near infrared? Red light (about 630–660 nm in most devices) is visible and absorbed mostly in the upper layers of skin. Near-infrared (about 830–850 nm) is mostly invisible and reaches deeper tissue.[8]

Is photobiomodulation the same as red light therapy? Yes. PBM, red light therapy and low-level light therapy are different names for the same field.[8]

Does ARTG inclusion mean a device works? No. ARTG inclusion is permission to supply. It isn’t a TGA endorsement.[2][26]

If you have questions about your skin, eyes or a health condition, speak with your GP or another health professional.

Related reading on our blog

• Photobiomodulation explained: the science behind red light
• 660nm and 850nm red light therapy: what buyers should know

Sources

1. ARPANSA. Advice for consumers: Lasers, IPL devices and LED phototherapy for cosmetic treatments and beauty therapy. https://www.arpansa.gov.au/understanding-radiation/sources-radiation/more-radiation-sources/lasers-and-intense-pulsed-light-0
2. TGA. Overview of applying for market authorisation. https://www.tga.gov.au/products/regulations-all-products/overview-applying-market-authorisation
3. TGA. Searching the Australian Register of Therapeutic Goods (ARTG). https://www.tga.gov.au/products/regulations-all-products/about-australian-register-therapeutic-goods-artg/searching-australian-register-therapeutic-goods-artg
4. ACCC. Consumer rights and guarantees. https://www.accc.gov.au/consumers/buying-products-and-services/consumer-rights-and-guarantees
5. ACCC. Repair, replace, refund, cancel. https://www.accc.gov.au/business/problem-with-a-product-or-service-you-sold/repair-replace-refund-cancel
6. de Freitas LF, Hamblin MR. Proposed mechanisms of photobiomodulation or low-level light therapy. IEEE Journal of Selected Topics in Quantum Electronics. 2016;22(3). https://doi.org/10.1109/JSTQE.2016.2561201
7. Sadowska M, Narbutt J, Lesiak A. Blue light in dermatology. Life (Basel). 2021;11(7):670. https://doi.org/10.3390/life11070670 (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC8307003/; cited for wavelength ranges and skin depth only)
8. Spongberg CV, Stack ER, Aprigliano C, Grinis D, Sawicki S, Elway M. What to look for in red light therapy: a product guide backed by science. Cureus. 2026;18(3):e105378. https://doi.org/10.7759/cureus.105378 (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC13085462/)
9. US FDA. Premarket Notification 510(k). https://www.fda.gov/medical-devices/premarket-submissions-selecting-and-preparing-correct-submission/premarket-notification-510k
10. US FDA. Premarket Approval (PMA); and Device Approvals and Clearances. https://www.fda.gov/medical-devices/premarket-submissions-selecting-and-preparing-correct-submission/premarket-approval-pma ; https://www.fda.gov/medical-devices/products-and-medical-procedures/device-approvals-and-clearances
11. International Commission on Non-Ionizing Radiation Protection (ICNIRP). ICNIRP statement on far infrared radiation exposure. Health Physics. 2006;91(6):630–645. https://www.icnirp.org/cms/upload/publications/ICNIRPinfrared.pdf
12. TGA. Advertising legal framework. https://www.tga.gov.au/products/regulations-all-products/advertising/advertising-legal-framework
13. TGA. Understanding regulation of off-label use of medical devices. https://www.tga.gov.au/resources/guidance/understanding-regulation-label-use-medical-devices
14. Heiskanen V, Hamblin MR. Photobiomodulation: lasers vs. light emitting diodes? Photochemical & Photobiological Sciences. 2018;17(8):1003–1017. https://doi.org/10.1039/c8pp90049c (open access: https://pmc.ncbi.nlm.nih.gov/articles/PMC6091542/)
15. Queensland Health. Laser licensing. https://www.health.qld.gov.au/public-health/industry-environment/personal-appearance/laser-licensing
16. Queensland Government. Understand the risks of light-based cosmetic services. https://www.qld.gov.au/health/conditions/all/prevention/beauty-therapy/light-based-cosmetic-services/risks
17. Das RK, Thayer WP, Kubiak CA, et al. Efficacy and safety of at-home light-emitting diode photobiomodulation for facial rejuvenation: a systematic review. Aesthetic Plastic Surgery. 2026. https://link.springer.com/article/10.1007/s00266-026-06333-w
18. Quirk BJ, Whelan HT. What lies at the heart of photobiomodulation: light, cytochrome c oxidase, and nitric oxide. Review of the evidence. Photobiomodulation, Photomedicine, and Laser Surgery. 2020. https://doi.org/10.1089/photob.2020.4905
19. Sommer AP. Revisiting the photon/cell interaction mechanism in low-level light therapy. Photobiomodulation, Photomedicine, and Laser Surgery. 2019. https://doi.org/10.1089/photob.2018.4606
20. Armitage H. Red light therapy: what the science says. Stanford Medicine. February 2025. https://med.stanford.edu/news/insights/2025/02/red-light-therapy-skin-hair-medical-clinics.html
21. Electrical Equipment Safety System (EESS). EESS registrations purpose. https://www.eess.gov.au/registration/eess-registrations-purpose/
22. Optometry Australia. Position statement on myopia management. 2024. https://www.optometry.org.au/wp-content/uploads/Professional_support/Guidelines/Myopia-Position-Statement-2024-v3.pdf
23. Richards J, Hunter JJ, Gantes-Nuñez J, Bradley A, Kollbaum P. Radiometric and safety assessment of a ‘low-level red-light’ myopia control device. Ophthalmic and Physiological Optics. 2025;45:1905–1911. https://doi.org/10.1111/opo.70009
24. ABC News (22 July 2026). The claims and evidence behind popular anti-aging and wellness treatments. https://www.abc.net.au/news/2026-07-22/peptides-red-light-nad-wellness-therapies-claims/106937662
25. TGA. Determining if your product is a cosmetic or therapeutic good. https://www.tga.gov.au/resources/guidance/determining-if-your-product-cosmetic-or-therapeutic-good
26. TGA. The claim “TGA approved” must not be used in advertising. https://www.tga.gov.au/products/regulations-all-products/advertising/specialised-advertising-issues-and-topics/claim-tga-approved-must-not-be-used-advertising
27. Therapeutic Goods (Therapeutic Goods Advertising Code) Instrument 2021, s 24(6)(a). https://www.legislation.gov.au/F2021L01661/2022-12-20/2022-12-20/text/original/pdf
28. Cancer Council NSW. What is UV radiation? https://www.cancercouncil.com.au/cancer-prevention/sun-protection/understanding-uv-radiation/what-is-uv-radiation/
29. ACCC. Warranties. https://www.accc.gov.au/consumers/buying-products-and-services/warranties