How Does Red Light Therapy Work? A Manufacturer's Guide to Photobiomodulation

Red light therapy, clinically called photobiomodulation (PBM), uses specific wavelengths of red (620–680 nm) and near-infrared (780–900 nm) light to stimulate biological activity inside cells. Photons are absorbed by cytochrome c oxidase in the mitochondrial electron transport chain, increasing ATP production, triggering nitric oxide release, and activating downstream signaling cascades. The result is measurable cellular activity with a well-documented safety profile. Published peer-reviewed research spans pain, inflammation, skin health, muscle recovery, and wound healing. Irradiance (the intensity of light delivered at the tissue surface), not just total energy, determines clinical outcome. This guide covers the mechanism from photon to cell to measurable effect.

What Is Photobiomodulation (PBM)?

The short answer: Photobiomodulation (PBM) is the use of non-ionizing red and near-infrared light to stimulate, heal, regenerate, or protect tissue. The mechanism is photochemical, not thermal: photons interact with specific molecular targets inside cells rather than burning or cutting tissue.

The term "photobiomodulation" was formally adopted by the North American Association for Laser Therapy (NAALT) and the World Association for Laser Therapy (WALT) to replace the earlier, imprecise term "low-level laser therapy" (LLLT).

PBM is distinct from other light therapies in two key respects. UV light (280–400 nm) and photodynamic therapy (PDT) either damage DNA or rely on photosensitizing drugs to destroy target tissue. Ablative lasers vaporize tissue at high power densities. PBM operates at 1–1,000 mW/cm², requires no photosensitizer, produces no tissue destruction, and uses the light itself as the therapeutic agent.

Body Balance System has operated in the photobiomodulation space for 13 years. The OvationULT Zero Gravity Bed is an FDA-registered Class II device (21 CFR 890.5500, FDA Registration #3010627475, Device Listing #877966, Product Code ILY). Every design specification reflects accumulated knowledge of how PBM parameters translate to reproducible outcomes in a commercial environment.

How Does Light Interact with Cells?

The short answer: Photons in the red and NIR range are absorbed by cytochrome c oxidase (CCO), a protein complex in the mitochondrial inner membrane. This absorption triggers increased electron transport, higher ATP synthesis, release of nitric oxide (NO), and controlled reactive oxygen species (ROS) signaling. This cascade modulates cellular metabolism and inflammation.

Cytochrome c Oxidase: The Primary Chromophore

The mechanism begins with absorption. For PBM to produce biological effects, photons must be absorbed by a specific molecular target, called a chromophore. The primary chromophore for red and near-infrared light in mammalian cells is cytochrome c oxidase (CCO), Complex IV of the mitochondrial electron transport chain.

CCO contains two copper centers (Cu_A and Cu_B) and two iron-porphyrin heme groups (heme a and heme a₃). These metal centers have absorption peaks that align closely with the therapeutic window of red and near-infrared light. When a photon is absorbed, it shifts CCO from a lower-activity state (partially inhibited by nitric oxide binding) to a higher-activity state.

Michael R. Hamblin, a leading PBM researcher at Harvard Medical School's Wellman Center for Photomedicine, published a foundational review of these mechanisms in AIMS Biophysics (2017), documenting the following cascade:

• Photon absorption by CCO triggers dissociation of inhibitory nitric oxide from the enzyme

• Increased electron transport through the respiratory chain drives greater proton gradient across the inner mitochondrial membrane, increasing ATP synthesis

• Released nitric oxide (NO) diffuses into surrounding tissue, producing vasodilation and improved local circulation

• Transient increase in reactive oxygen species (ROS) at sub-damaging levels activates antioxidant defense pathways and redox-sensitive transcription factors (NF-kB, AP-1)

• Upregulation of cytoprotective genes and growth factors follows downstream

This cascade explains why PBM can support both acute and chronic processes: initial signaling events are rapid (seconds to minutes), while downstream gene expression changes develop over hours to days.

Secondary Chromophores

Research has also identified light-sensitive ion channels as secondary chromophores, particularly transient receptor potential (TRP) channels that respond to near-infrared wavelengths and mediate calcium ion influx. This secondary pathway activates signaling cascades governing cellular proliferation and migration, and may account for some tissue effects observed at longer NIR wavelengths.

Hamblin MR. "Mechanisms and applications of the anti-inflammatory effects of photobiomodulation." AIMS Biophysics. 2017;4(3):337-361. doi: 10.3934/biophy.2017.3.337. PMID: 28748217. https://pubmed.ncbi.nlm.nih.gov/28748217/ 

Which Wavelengths Matter and Why?

The short answer: Red (620–680 nm) and near-infrared (780–900 nm) occupy the "optical window" of biological tissue: long enough to avoid high UV-range absorption by melanin and short enough to avoid deep infrared absorption by water. Within this window, 635 nm and 850 nm have the most robust research bases for therapeutic applications.

The Optical Window of Tissue

Light interacts with tissue through reflection, scattering, absorption, and transmission. The therapeutic utility of any wavelength depends on how deeply it penetrates before being fully absorbed or scattered. Four primary tissue absorbers govern this:

• Melanin (skin): absorbs strongly in UV and visible spectrum, decreasing above ~600 nm

• Oxyhemoglobin and deoxyhemoglobin: absorption peaks below 600 nm with sharp reduction above

• Water: absorbs strongly above ~950 nm

• Lipids: modest absorption across the visible spectrum

Between ~600 nm and ~950 nm, all major absorbers decline simultaneously, creating the "biological optical window" where light penetrates most effectively. This is why PBM does not use UV, visible blue/green, or far-infrared wavelengths for deep tissue applications.

Wavelength Penetration Comparison

Why 635 nm and 850 nm?

These two wavelengths are not arbitrary. They represent the most extensively studied wavelengths in peer-reviewed PBM research.

635 nm falls at a CCO absorption peak and has been used in the majority of skin health, wound healing, and pain studies going back to the 1980s. It is a wavelength at which irradiance can be quantified reliably and for which dose-response data is well established.

850 nm penetrates significantly deeper than red wavelengths and accesses CCO via a different absorption peak. It is the dominant wavelength in musculoskeletal PBM research, particularly studies on muscle recovery, joint pain, and deep tissue effects.

The OvationULT Zero Gravity Bed is built with 22,755 red diodes at 635 nm and 5,688 NIR diodes at 850 nm, delivering a combined irradiance of 65 mW/cm² at the body surface. This specific combination reflects both the published research base and 13 years of commercial application data.

Heiskanen V, Hamblin MR. "Photobiomodulation: lasers vs. light emitting diodes?" Photochem Photobiol Sci. 2018;17(8):1003-1017. doi: 10.1039/c8pp90049c. PMID: 30044464. https://pubmed.ncbi.nlm.nih.gov/30044464/ 

What Does the Published Research Show?

The short answer: PBM research spans more than five decades and thousands of peer-reviewed publications. The strongest evidence base covers pain and inflammation management, skin health, muscle recovery, and wound healing. The following summarizes key published research areas. These findings represent what the scientific literature reports: they are not claims about the OvationULT or any specific clinical outcomes achievable with BBS equipment.

Pain and Inflammation

A systematic review by Bjordal et al. (2003), published in the Australian Journal of Physiotherapy, analyzed 88 randomized controlled trials of low-level laser therapy for pain from chronic joint disorders. The authors found statistically significant reductions in pain scores across studies that delivered doses within a defined therapeutic window. The review specifically noted that studies delivering sub-therapeutic doses showed weaker effects, underscoring the importance of dosimetric precision.

Bjordal JM, Couppé C, Chow RT, Tunér J, Ljunggren EA. "A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders." Aust J Physiother. 2003;49(2):107-116. doi: 10.1016/s0004-9514(14)60127-6. PMID: 12775206. https://pubmed.ncbi.nlm.nih.gov/12775206/ 

Hamblin's 2017 review (cited above) further established that PBM anti-inflammatory effects operate through multiple parallel pathways: reduced pro-inflammatory cytokine production (TNF-a, IL-1b, IL-6), increased anti-inflammatory cytokine production (IL-10), inhibition of COX-2 expression, and reduction of nuclear NF-kB activation in activated macrophages.

Skin Health

A comprehensive review by Avci et al. (2013) in Seminars in Cutaneous Medicine and Surgery documented evidence for improved wound healing and overall cellular repair within the dermis. The photobiological mechanism involves the same CCO-ATP pathway: skin fibroblasts, which are mitochondria-rich, respond to PBM with measurable increases in cellular energy, supporting the body's natural tissue repair processes and reducing oxidative stress. 

Avci P, Gupta A, Sadasivam M, et al. "Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring." Semin Cutan Med Surg. 2013;32(1):41-52. PMID: 24049929. PMCID: PMC4126803. https://pmc.ncbi.nlm.nih.gov/articles/PMC4126803/ 

Muscle Recovery and Athletic Performance

A comprehensive review by Ferraresi, Huang, and Hamblin (2016), published in the Journal of Biophotonics, examined 46 studies on PBM and human muscle tissue. The review found consistent evidence that PBM applied before or after exercise can reduce delayed-onset muscle soreness (DOMS), accelerate lactate clearance, reduce creatine kinase release (a marker of muscle damage), and support faster return to baseline strength. The proposed mechanism includes both the direct ATP/mitochondrial pathway and secondary anti-inflammatory signaling.

Ferraresi C, Huang YY, Hamblin MR. "Photobiomodulation in human muscle tissue: an advantage in sports performance?" J Biophotonics. 2016;9(11-12):1273-1299. doi: 10.1002/jbio.201600176. PMID: 27874264. PMCID: PMC5167494. https://pubmed.ncbi.nlm.nih.gov/27874264/ 

Wound Healing

PBM's wound-healing applications are among the most extensively studied. The mechanism involves increased fibroblast proliferation and migration, upregulation of growth factors (VEGF, EGF, bFGF), stimulation of keratinocyte proliferation for re-epithelialization, and modulation of inflammatory phase duration. The evidence is particularly strong for diabetic ulcers, post-surgical wounds, and radiation-induced tissue injury.

How Does Irradiance Affect Treatment Outcomes?

The short answer: Irradiance (the power of light delivered per unit area, measured in mW/cm²) is the critical variable most often misunderstood in commercial red light therapy. Too little produces no measurable effect. Too much can inhibit cellular activity. The optimal range is application-specific, but 50–100 mW/cm² at the tissue surface is well supported by the literature for full-body applications.

The Biphasic Dose Response (Arndt-Schulz Curve)

PBM follows a biphasic, or hormetic, dose-response curve. At sub-threshold doses, there is insufficient photon flux to activate CCO or trigger meaningful signaling. At optimal doses, the signaling cascade produces measurable outcomes. At supra-threshold doses, excessive photon flux causes mitochondrial overactivation, elevated ROS beyond the signaling threshold, and paradoxical inhibition of the same pathways stimulated at lower doses.

This is why "more is better" is false in PBM. A device delivering 200 mW/cm² at contact is not automatically more effective than one delivering 65 mW/cm²; at some dose levels, it may produce inferior outcomes.

Contact Irradiance vs. Distance Irradiance

Irradiance measurements are meaningless without specifying the distance at which they were taken. Due to the inverse square law, light intensity falls off as the square of the distance from the source. A device measuring 100 mW/cm² at the emitter surface may deliver only 25 mW/cm² at 10 cm and less than 10 mW/cm² at 20 cm.

The OvationULT positions the client 2–3 inches from the diode array. This proximity is engineered to deliver the stated 65 mW/cm² irradiance consistently at the body surface. When evaluating any commercial PBM device, the relevant question is: at what distance was the irradiance figure measured?

LEDs vs. Lasers: What's the Difference for Commercial Use?

The short answer: Both lasers and LEDs produce photobiomodulation effects when matched to the same wavelength and dose. For commercial applications, LEDs offer practical advantages: larger treatment area per unit, lower cost, no eye safety classification issues with properly designed beds, and suitability for unattended use.

The key technical distinction is coherence. Lasers emit coherent, monochromatic light with all photons traveling in phase. LEDs emit non-coherent, quasi-monochromatic light with slight wavelength bandwidth (typically ±10–20 nm). For decades, PBM researchers debated whether coherence was essential to the biological effect.

Heiskanen and Hamblin's 2018 review in Photochemical & Photobiological Sciences addressed this directly. Their conclusion: at equivalent wavelengths, irradiances, and doses, LEDs and lasers produce comparable photobiomodulation effects. Coherence does not appear to be a mechanistically necessary property for PBM outcomes.

LED vs. Laser Comparison

Heiskanen V, Hamblin MR. "Photobiomodulation: lasers vs. light emitting diodes?" Photochem Photobiol Sci. 2018;17(8):1003-1017. doi: 10.1039/c8pp90049c. PMID: 30044464. https://pubmed.ncbi.nlm.nih.gov/30044464/ 

What Makes Full-Body Delivery Different from Panels?

The short answer: Full-body simultaneous exposure delivers a photon dose across the entire skin surface in a single session. Panel-based treatments cover one body region at a time, requiring repositioning and multiple sessions to achieve equivalent total-body coverage. Consistent proximity to the light source is the other critical variable.

A single 10-minute session on a full-body bed delivers PBM simultaneously to the anterior and posterior torso, extremities, face, and neck. Equivalent coverage with a 12"x24" panel requires sequential repositioning across 8–12 body segments, totaling 80–120 minutes of exposure time.

From a research standpoint, several systemic effects documented in PBM literature, including anti-inflammatory signaling and circulatory changes, are proposed to involve systemic rather than purely local mechanisms. Full-body exposure maximizes the area of cellular activation. From an operator standpoint, 10-minute full-body sessions versus 90-minute sequential panel sessions represent entirely different business models.

Proximity remains the dominant variable. The inverse square law is not a theoretical concern: a panel positioned 18 inches from the body delivers approximately 1/36th the irradiance of the same panel at 3 inches. The OvationULT's zero-gravity recline positions the client 2–3 inches from the 28,443-diode array, delivering 65 mW/cm² at the body surface. That figure is measured and reproducible, achieved by engineering proximity into the mechanical design of the bed. The relevant question for operators evaluating any equipment is not how many diodes a device has: it is what irradiance is delivered at the actual client-to-device distance during use.

Frequently Asked Questions About Red Light Therapy Science

Is red light therapy the same as infrared sauna?

No. Infrared saunas use far-infrared radiation (3,000–100,000 nm) to produce heat: the therapeutic effect is thermal, operating through elevated core temperature, sweating, and cardiovascular responses. Photobiomodulation uses red (620–680 nm) and near-infrared (780–900 nm) light at sub-thermal intensities, and the mechanism is photochemical, not thermal. A PBM session does not produce meaningful core temperature increase. The two are complementary modalities, not substitutes.

How long does a red light therapy session take?

Session length depends on irradiance and the dose target. At 65 mW/cm², a session of 10–20 minutes delivers 39–78 J/cm² to the body surface: a range that encompasses the effective doses used in published human studies. Higher irradiance allows shorter sessions to deliver equivalent doses; lower irradiance requires longer sessions. Devices with very low or unmeasured irradiance may require impractically long sessions to deliver any therapeutically meaningful dose.

Is red light therapy safe?

PBM has an extensive safety record across five decades of published research. It produces no ionizing radiation, no thermal damage at therapeutic irradiances, and no known systemic toxicity. Standard precautions include avoiding direct eye exposure to the light source and following device-specific protocols for populations with photosensitivity conditions. The OvationULT is an FDA-registered Class II device (21 CFR 890.5500) certified by SGS North America (NRTL), indicating it meets established electrical and photobiological safety standards.

Does red light therapy work through clothing?

No, or minimally. Clothing absorbs and scatters light before it reaches the skin. Dark or thick fabrics can block 90% or more of incident light. For therapeutic effect, the target tissue must be directly exposed.

What is the difference between red light and near-infrared?

Both are in the PBM therapeutic window, but they differ in penetration depth and primary targets. Red light (620-680 nm) penetrates 3-6 mm, reaching the dermis, superficial capillary beds, and outer layers of muscle. Near-infrared (780-900 nm) penetrates 10-30 mm, reaching deep muscle tissue, connective tissue, and periarticular structures. Systems combining both wavelengths provide coverage of both superficial and deep tissues. This is the rationale behind the OvationULT's 635 nm + 850 nm dual-wavelength architecture. 

Full Citations

Hamblin MR. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics. 2017;4(3):337-361. doi: 10.3934/biophy.2017.3.337. PMID: 28748217. PMCID: PMC5523874. https://pubmed.ncbi.nlm.nih.gov/28748217/ 

Heiskanen V, Hamblin MR. Photobiomodulation: lasers vs. light emitting diodes? Photochem Photobiol Sci. 2018;17(8):1003-1017. doi: 10.1039/c8pp90049c. PMID: 30044464. PMCID: PMC6091542. https://pubmed.ncbi.nlm.nih.gov/30044464/ 

Bjordal JM, Couppé C, Chow RT, Tunér J, Ljunggren EA. A systematic review of low level laser therapy with location-specific doses for pain from chronic joint disorders. Aust J Physiother. 2003;49(2):107-116. doi: 10.1016/s0004-9514(14)60127-6. PMID: 12775206. https://pubmed.ncbi.nlm.nih.gov/12775206/ 

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;32(1):41-52. PMID: 24049929. PMCID: PMC4126803. https://pmc.ncbi.nlm.nih.gov/articles/PMC4126803/ 

Ferraresi C, Huang YY, Hamblin MR. Photobiomodulation in human muscle tissue: an advantage in sports performance? J Biophotonics. 2016;9(11-12):1273-1299. doi: 10.1002/jbio.201600176. PMID: 27874264. PMCID: PMC5167494. https://pubmed.ncbi.nlm.nih.gov/27874264/