Introduction
How light therapies work
Cellular and molecular effects
Skin and tissue regeneration
Muscle recovery and performance
Pain and inflammation management
Systemic and emerging applications
Safety and practical use
Limitations and research gaps
Conclusions
References
Further reading
Photobiomodulation uses red and near-infrared light to modulate mitochondrial activity, cellular signaling, and inflammatory pathways, supporting tissue repair and physiological recovery. Clinical research suggests potential benefits across dermatology, pain management, metabolic health, neurological function, and circadian regulation, although standardized treatment protocols remain under investigation.
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Introduction
Photobiomodulation (PBM), previously referred to as low-level light therapy (LLLT), utilizes non-thermal visible red and near-infrared wavelengths typically within the 600–1100 nm spectrum to modulate cellular activity and biological repair processes. Photobiomodulation utilizes specific wavelengths of red and near-infrared light to target mitochondrial cytochrome c oxidase, thereby stimulating tissue repair, attenuating systemic inflammation, and accelerating physiological recovery. Recent clinical data highlight the therapeutic potential of photobiomodulation for broad systemic applications, including muscle regeneration, chronic pain modulation, metabolic syndrome regulation, and circadian rhythm entrainment.1,5
This article examines the cellular mechanisms by which targeted light therapy induces physiological changes that promote systemic healing, disease management, and performance optimization.
How light therapies work
Photobiomodulation is a non-invasive therapeutic modality that leverages non-ionizing light sources, especially lasers and light-emitting diodes, as cellular catalysts to support endogenous repair processes.1 When target tissues are exposed to specific therapeutic wavelengths, photons are absorbed by endogenous photoreceptors like cytochrome c oxidase, the primary photoreceptor in the electron transport chain.2
Photon absorption by cytochrome c oxidase can also promote the photodissociation of nitric oxide (NO) from the enzyme complex, restoring mitochondrial respiration and improving cellular oxygen utilization.2 Photobiomodulation operates within red and near-infrared optical wavelengths to influence biological processes without generating thermal damage or cellular cytotoxicity.1 The depth of tissue penetration and, subsequently, the therapeutic benefits of light therapy primarily depend on the wavelength of applied light.
Superficial chromophores, such as melanin and hemoglobin, absorb red light within the 20-700 nm range, making this form of light therapy optimal for epidermal and dermal targeting.1 Comparatively, near-infrared wavelengths of 700-1100 nm exhibit less optical scattering and water absorption than red light, allowing these photons to penetrate deeper into subcutaneous adipose tissue, skeletal muscle, and the brain.1
Cellular and molecular effects
Photoactivation of cytochrome c oxidase increases mitochondrial membrane potential in the electron transport chain, thereby enhancing adenosine triphosphate (ATP) production in experimental and preclinical models.2 In addition to supporting sustained energy production, photobiomodulation provides dose-dependent antioxidant effects by mitigating oxidative stress, particularly in pathologically inflamed tissues.
Higher doses of light therapy induce a mild, transient increase in reactive oxygen species (ROS) generation, which promotes cellular growth and strengthens endogenous antioxidant defenses.3 Thus, photobiomodulation manipulates critical cellular signaling to suppress the pro-inflammatory nuclear factor κB (NF-κB) pathway while activating pathways that promote cell survival and tissue remodeling.2
Importantly, PBM responses often follow a biphasic dose–response relationship, sometimes described by the Arndt–Schulz law, in which low or moderate doses stimulate cellular activity while excessively high doses may produce reduced or inhibitory biological effects.2
How Does Red Light Therapy Work?
Skin and tissue regeneration
In dermatology, photobiomodulation optimizes the inflammatory phase of wound healing by facilitating macrophage transition from a pro-inflammatory to a tissue-resolving state.1 Specifically, red light therapy upregulates the synthesis of Type I and Type III collagen, downregulates the expression of enzymes that degrade the tissue matrix, and stimulates the formation of new blood vessels to promote faster skin healing.1
Crucially, analyses of clinical markers have validated the effectiveness of light therapy in accelerating the closure of chronic wounds, reducing the appearance of raised scars, and providing aesthetic skin rejuvenation. Taken together, these benefits are attributed to the ability of photobiomodulation to enhance tissue elasticity without the thermal damage typically associated with ablative lasers.1
Clinical studies have also investigated PBM for dermatologic conditions, including acne, androgenetic alopecia, radiation dermatitis, and scar remodeling, although treatment responses and optimal dosing parameters vary among indications.1
When applied before exercise, photobiomodulation improves muscular performance and delays the onset of fatigue.3 In a recent meta-analysis, athletes receiving photobiomodulation treatment reported significantly reduced perceived muscle pain at both 72 and 96 hours after exercise.
Specifically, photobiomodulation significantly accelerated the recovery of athletes’ muscular strength while reducing circulating blood lactate and creatine kinase levels, suggesting these effects are due to improvements in microcirculation and ATP production.3
However, many sports performance studies remain limited by small sample sizes and heterogeneous treatment protocols, which may influence the consistency of reported performance benefits.3
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Pain and inflammation management
As an intervention for pain relief, photobiomodulation has been shown to alter patients’ local biochemical environment by suppressing pro-inflammatory cytokines, such as interleukin 1β (IL-1β), IL-6, and tumor necrosis factor α (TNF-α).4
Moreover, a recent systematic review of data from over 9,000 participants suggests that photobiomodulation promotes the release of neuromodulators, such as serotonin, to mitigate pain sensitivity.5
Herein, photobiomodulation therapy reduced fatigue among fibromyalgia patients with a strong clinical effect size of 1.25, whereas disability management in knee osteoarthritis led to a moderate, yet significant, effect size of 0.65.5
Nevertheless, several analyses report that the certainty of evidence for many clinical indications remains moderate or low due to study heterogeneity and potential publication bias.5
Systemic and emerging applications
Randomized controlled trials (RCTs) investigating the therapeutic potential of photobiomodulation for metabolic health and obesity indicate that applying red and near-infrared light b(33 -40 nm )to the abdomen may influence metabolic and inflammatory markers.6
Among obese patients, photobiomodulation interventions have been shown to significantly reduce body mass index (BMI) values by an average of 1.18 points, total body weight by 3.54 kilograms, total cholesterol by 23 mg/dL, and insulin resistance (IR) metrics by 0.46 points.6
Photobiomodulation interventions also may contribute to improved vascular function by increasing nitric oxide availability and promoting vasodilation, which could help reduce blood pressure levels in both animal models and human patients.7
A systematic review investigating the impact of photobiomodulation on shift workers with severe sleep disruption demonstrated that carefully timed moderate-intensity light exposure effectively reset their internal clocks.
This resetting mechanism translates to a 32.5-minute increase in total sleep time and 3% improvement in overall sleep efficiency.8
Neurologically, transcranial near-infrared stimulation of 810-1,072 nm can effectively penetrate the skull to reduce brain inflammation and prevent the accumulation of harmful proteins.
Early clinical investigations suggest that PBM may improve certain cognitive functions, although larger randomized trials are required to confirm these effects.5
While not validated in human cohorts, preclinical models suggest that 670-830 nm light therapy can mitigate oxidative stress in chronic kidney disease by restoring mitochondrial DNA and enhancing antioxidant enzymes, thereby limiting the systemic spread of uremic toxins.9
Safety and practical use
As a non-invasive therapy that does not cause heat or cellular destruction, photobiomodulation maintains a strong safety profile.
Even among highly vulnerable patients, the World Association for Photobiomodulation Therapy (WALT) officially recommends its use for managing severe oncology complications, such as radiation dermatitis and oral mucositis.10
These clinical guidelines highlight PBM as an evidence-supported supportive therapy in oncology care when appropriate treatment parameters are used.10
Limitations and research gaps
To date, most RCTs have used significantly different photomodulation doses, with variations in wavelength, power density, total energy delivered, and treatment schedules.
This substantial variability in treatment protocols, irradiation parameters, and clinical populations remains a major challenge for establishing standardized PBM dosing guidelines.4,5
This lack of standardization eunderscoresthe need for large-scale RCTs aacrossdiverse populations to establish precise dosing guidelines for specific conditions and vto alidate long-term patient outcomes.1,4
Conclusions
Photobiomodulation interventions directly influence mitochondrial energy production, redox signaling, and inflammatory pathways, thereby delivering quantifiable benefits ranging from tissue repair and athletic recovery to metabolic optimization and cognitive support.
Although growing evidence supports several therapeutic applications of PBM, the overall strength of clinical evidence varies across indications, and additional high-quality randomized trials are required before these therapies can be broadly integrated into routine clinical practice.
- Hernández-Bule, M. L., Naharro-Rodríguez, J., Bacci, S., & Fernández-Guarino, M. (2024). Unlocking the Power of Light on the Skin: A Comprehensive Review on Photobiomodulation. International Journal of Molecular Sciences 25(8); 4483. DOI: 10.3390/ijms25084483. https://www.mdpi.com/1422-0067/25/8/4483
- Al Balah, O. F., Rafie, M., & Osama, A.-R. (2025). Immunomodulatory effects of photobiomodulation: a comprehensive review. Lasers in Medical Science 40(1). DOI: 10.1007/s10103-025-04417-8. https://link.springer.com/article/10.1007/s10103-025-04417-8
- Tsou, Y., Chang, N., & Chang, W.-D. (2025). Effects of Photomodulation Therapy for Delayed Onset Muscle Soreness: A Systematic Review and Meta-Analysis. Journal of Functional Morphology and Kinesiology 10(3); 277. DOI: 10.3390/jfmk10030277. https://www.mdpi.com/2411-5142/10/3/277
- Ferreira, L. M. A., Oliveira, A. B. C., Mendes, J. J. B., et al. (2026). Photobiomodulation in chronic pain: a systematic review of randomized clinical trials. Frontiers in Integrative Neuroscience 20. DOI: 10.3389/fnint.2026.1717372. https://www.frontiersin.org/journals/integrative-neuroscience/articles/10.3389/fnint.2026.1717372/full
- Son, Y., Lee, H., Yu, S., et al. (2025). Effects of photobiomodulation on multiple health outcomes: an umbrella review of randomized clinical trials. Systematic Reviews 14(1). DOI: 10.1186/s13643-025-02902-3. https://www.mdpi.com/2411-5142/10/3/277
- Sun, W., Zhuang, Z., Yang, L., et al. (2025). Effectiveness of photobiomodulation therapy in improving health indicators in obese patients: a systematic review and meta-analysis of RCTs. BMC Complementary Medicine and Therapies 25(1). DOI: 10.1186/s12906-025-04874-2. https://link.springer.com/article/10.1186/s12906-025-04874-2
- Bataglia Espósito, L. M., Costa da Rocha, F., Arany, P. R., & Ferraresi, C. (2025). Photobiomodulation Therapy in Hypertension Management - Evidence from a Systematic Review and Meta-Analysis. Journal of Clinical Medicine 14(19); 6716. DOI: 10.3390/jcm14196716. https://www.mdpi.com/2077-0383/14/19/6716
- Zhao, C., Li, N., Miao, W., et al. (2025). A systematic review and meta-analysis on light therapy for sleep disorders in shift workers. Scientific Reports; 15(1). DOI: 10.1038/s41598-024-83789-3. https://www.nature.com/articles/s41598-024-83789-3
- Bian, J., Liebert, A., Bicknell, B., et al. (2022). Therapeutic Potential of Photobiomodulation for Chronic Kidney Disease. International Journal of Molecular Sciences 23(14); 8043. DOI: 10.3390/ijms23148043. https://www.mdpi.com/1422-0067/23/14/8043
- Robijns, J., Nair, R. G., Lodewijckx, J., et al. (2022). Photobiomodulation therapy in management of cancer therapy-induced side effects: WALT position paper 2022. Frontiers in Oncology 12. DOI: 10.3389/fonc.2022.927685. https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2022.927685/full
Further Reading
Last Updated: Mar 15, 2026