Photobiomodulation: Studies from July and August 2026

Two months of posts, one common thread: the dose

July and August 2026 were by no means a summer lull for research on photobiomodulation (PBM).

Between July 1 and August 31, 215 references were retrieved from PubMed for the search terms “photobiomodulation,” “low-level laser therapy,” and “red light therapy.” After removing false positives and articles that actually dealt with ablative, vascular, or cosmetic lasers, 117 studies are cited here, each with its DOI link.

Two findings are worth noting right away, because they point in opposite directions: a human muscle study that found no effect on mitochondrial respiration, and a study on childhood myopia that yielded the clearest clinical result of the past two months.

One theme runs through this period, and it is more interesting than a mere accumulation of findings: the relationship between dose and effect is not linear. Several independent studies, both in humans and in cell cultures, show that beyond a certain threshold, light ceases to be beneficial and may even be harmful. This is a nuance that the marketing discourse on red light often overlooks, and we believe it deserves to be highlighted rather than concealed.

Here is our breakdown by topic, with links to the original articles.

Table of Contents

• It's the dose that makes the difference—but not in the way you might think
• Pain and the Musculoskeletal System
• Oncology and supportive care
• Neurology and Cognition
• Oral Health
• Wound Healing and Chronic Wounds
• Dermatology and Aesthetics
• Ophthalmology
• Sports, Recovery, and Cellular Mechanisms
• Emerging Findings and Tools
• Frequently Asked Questions
• Key Takeaways

It's the dose that makes the difference—but not in the way you might think

The most robust result of the summer comes from a randomized sham-controlled trial published in *Brain Stimulation*. In 31 patients with depression, prefrontal 808-nm transcranial PBM was administered under MRI guidance in a four-arm design: sham, high-dose pulsed, medium-dose continuous at approximately 300 mW/cm², and low-dose continuous at approximately 50 mW/cm². The medium dose significantly increased the BOLD signal strength, the low dose decreased it, and the pulsed arm had no effect. No single session altered depressive severity, and all three doses were well tolerated (DOI).

A second human study using functional MRI, published in the *Journal of Cerebral Blood Flow and Metabolism*, varied wavelength, irradiance, and pulse frequency, and introduced skin phototype as a dosimetric variable. The responses are not confined to the irradiated site: they spread to distal regions, and some persist after stimulation ceases. The numerical parameters are not included in the abstract, which makes it necessary to read the full text before drawing any conclusions (DOI).

Three in vitro studies support these observations. Consider C2C12 murine myoblasts preconditioned by PBM combined with a static magnetic field. The response is clearly hormetic: 9 J completely restores viability and normalizes reactive oxygen species, 30 J provides only partial protection, and 60 J increases the oxidative burden per surviving cell (DOI). Arany’s team subjected odontoblasts to five types of stress, then compared four wavelengths at 0.03, 3, and 30 J/cm². Only the intermediate dose of 3 J/cm² improved viability. Red at 658 nm and green at 532 nm provided the most consistent survival (DOI). In adipose-derived stem cells, the combination of 525 and 825 nm at 5 J/cm² increased ATP production without cytotoxicity, but metabolic activity decreased beyond that level (DOI).

A study on the Drosophila retina adds a useful layer of insight. Comparing 850 and 950 nm at 1, 4, 11, and 20 J/cm², the authors found that 850 nm restores photoreceptor function in a dose-dependent manner, whereas 950 nm fails to do so at any dose. However, ATP levels rise in both cases, with no correlation to functional recovery. In other words, ATP is not a sufficient marker of efficacy (DOI).

Desmettre and Mordon propose a conceptual framework that ties all of this together: the response would depend on the interaction between a dose-dependent bioenergetic window and the residual mitochondrial reserve of the target cells. This framework was developed for macular degeneration, but it also explains why studies conducted on very different tissues yield conflicting results (DOI).

Pain and the Musculoskeletal System

A systematic review registered in PROSPERO provides an overview of rehabilitation following total knee or hip replacement. Among 4 randomized trials involving a total of 133 patients, with PEDro scores ranging from 8 to 10, physical therapy improved postoperative pain and swelling in 3 trials, and joint range of motion and functional outcomes in 2. The authors nevertheless consider the evidence insufficient due to the heterogeneity of the study parameters (DOI).

In a randomized trial of 100 patients with chronic cervical myofascial syndrome, low-intensity laser acupuncture was compared with dry needling, both used as adjuncts to physical therapy. Both approaches significantly improve pain, cervical dysfunction, range of motion, and quality of life, albeit with different kinetics. For patients who are reluctant to undergo needle treatment, the equivalence of these approaches is a compelling argument (DOI).

The counterexample is just as instructive. A double-blind, sham-controlled trial involving 52 adults with chronic trapezius pain, who received 8 sessions of 808-nm laser therapy at 16 J per trigger point, found no difference in pain, the number of trigger points, or skin temperature. Both groups showed clinically meaningful improvement. Only cervical function improved significantly in the laser group (DOI).

A three-arm randomized pilot trial is investigating diabetic peripheral neuropathy, with 26 participants assigned to local PBM, PBM combined with intravascular blood irradiation, or a sham treatment. This condition is poorly responsive to medication, which justifies following this study (DOI). Another protocol is worth keeping an eye on. Published in BMJ Open, this multicenter, triple-blind trial plans to enroll 86 adults with chronic nonspecific knee pain, who will receive 12 treatments over 4 weeks. The device combines a 905-nm super-pulsed laser, 850-nm LEDs, 640-nm LEDs, and a static magnetic field (DOI).

Regarding the temporomandibular joint, a PRISMA-compliant systematic review of 18 trials involving 871 patients concluded that non-pharmacological interventions, including low-intensity laser therapy, produce more consistent and longer-lasting improvements than medications, whose benefits fade after 4 to 6 weeks (DOI). A comparative study also shows that LLLT used as an adjunct to arthrocentesis is more effective than arthrocentesis alone in reducing pain and improving mandibular mobility (DOI).

Two broader findings are worth noting. A controlled cohort study of 216 patients with degenerative musculoskeletal conditions reported multi-domain improvement with PBM combined with structured rehabilitation, and a favorable shift of approximately 3 years in functional age; the absence of a monotherapy arm prevents attributing the effect to light alone (DOI). Conversely, a systematic review of 4 trials involving 473 women concludes that the evidence is insufficient to recommend routine PBM after cesarean section, with low to very low certainty (DOI).

La série la plus intéressante vient de la réanimation cardiaque. Sur 264 patients opérés par sternotomie, 80 ont reçu de la lumière rouge dans les deux heures suivant l'admission en soins intensifs, 184 servant de témoins. L'incidence de douleur aiguë tombe à 38,8 % contre 57,1 % (p < 0,05), les scores CPOT baissent et la consommation d'opioïdes rapportée au poids diminue significativement. Aucune différence en revanche sur le drainage postopératoire ni sur les troubles de cicatrisation. L'analyse est rétrospective et monocentrique, avec un groupe contrôle non randomisé issu de la même période de recrutement, mais l'épargne morphinique après chirurgie cardiaque est un critère qui compte. Wang Y et al., Pain Research and Management (DOI 10.1155/prm/5561041)

In contrast, a systematic review with meta-analysis of photobiomodulation combined with exercise in fibromyalgia found no effect on any of the following measures: pressure pain threshold (mean difference -0.36; p = 0.54), pain intensity (1.07; p = 0.32), 6-minute walk test (-81.92; p = 0.30), FIQ questionnaire (p = 0.65), BDI score (p = 0.78), and SF-36 quality of life (p = 0.40). Heterogeneity reached 95%, which primarily reflects study protocols that were too disparate to be combined. Macena RL et al., British Journal of Pain (DOI 10.1177/20494637261471068)

Une étude pilote monobras a par ailleurs exposé 40 adultes à un panneau LED corps entier 630, 660, 830 et 850 nm, 20 minutes, dix séances. La charge douloureuse totale, estimée a posteriori et non mesurée directement, l'échelle n'ayant pas été répétée à l'identique après traitement, passe d'une médiane de 6,0 à 3,5 (p < 0,001), et 35 des 38 répondants (92,1 %) rapportent une amélioration globale. Sans groupe contrôle, sur des critères déclaratifs et avec un score final estimé, l'effet placebo n'est pas séparable de l'effet du traitement : nous citons ce travail pour la faisabilité, pas pour l'efficacité. Scoz RD et al., Photobiomodulation, Photomedicine and Laser Surgery (DOI 10.1177/25785478261481618)

In experimental neuropathic pain, photobiomodulation at 904 nm initiated on the fourteenth day following chronic sciatic nerve constriction in rats restores nerve growth factor levels and increases the expression of myelin P0 protein. Neither p-value nor dose in J/cm² are provided. Oliveira ME et al., Current Issues in Molecular Biology (DOI 10.3390/cimb48080806)

Oncology and supportive care

Le résultat le plus solide de la période en soins de support vient d'un essai de phase II, randomisé, en double aveugle et contrôlé par laser sham. Cinquante-trois patients atteints d'hémopathie maligne et traités par méthotrexate à haute dose ont été répartis entre photobiomodulation (n = 26) et placebo (n = 27). À 96 heures, la mucite ulcérée de grade 2 ou plus touche 11,5 % du groupe traité contre 51,9 % du groupe placebo, soit une réduction du risque relatif de 77,7 % et un nombre de sujets à traiter de 2 (p < 0,01). Le groupe placebo présentait un odds 8,97 fois plus élevé de mucite sévère. Les auteurs relèvent par ailleurs que le méthotrexate sérique n'était pas associé à la survenue de la mucite, alors que le méthotrexate salivaire augmentait de façon disproportionnée et corrélait indépendamment à la sévérité, ce qui en ferait un biomarqueur à valider. Rodrigues-Oliveira L et al., Oral Diseases (DOI 10.1111/odi.70381)

The POMFITT trial supports these findings in a different population and with a less stringent comparator—standard care rather than a sham laser. In 30 patients who underwent hematopoietic stem cell transplantation, using a 660- and 808-nm diode laser delivering 2 J at 20 points, severe oral mucositis occurred in 0% of the PBM group compared with 26.6% in the standard-of-care group (p = 0.032), with excellent tolerability. However, no effect was demonstrated on physical function (DOI).

A randomized non-inferiority protocol raises a very specific question: Can intraoral PBM be replaced by transcutaneous application? Fifty-four patients treated with radiation therapy at doses of 60 to 70 Gy will be randomized to receive either 660 nm intraorally at 44 points or 808 nm transcutaneously at 32 points. The application time would decrease from 440 to 80 seconds, which would affect feasibility in routine hospital practice (DOI).

A narrative review on oncology rehabilitation ranks PBM among the best-supported modalities, alongside TENS and neuromuscular electrical stimulation, emphasizing individualized dosimetry (DOI). A bibliometric analysis of the 100 most-cited articles between 1993 and 2025 confirms that oral mucositis remains the most mature application in the field, driven by the United States and Brazil (DOI).

Two studies temper this enthusiasm. In a mouse model of triple-negative breast cancer, adding a single session of red laser therapy to gold nanobrachytherapy provided no additional therapeutic benefit (DOI). And a review on salivary dysfunction notes that the response to PBM depends on the underlying cause: Sjögren’s syndrome, chemotherapy-induced toxicity, radiation-induced damage, and drug-induced hyposialia do not respond in the same way, and symptomatic improvement may occur without normalization of salivary flow (DOI).

A publication from this period does not provide any new clinical data; rather, it reexamines previous findings. Five studies frequently cited as evidence that photobiomodulation stimulates tumors were reanalyzed from a dosimetric perspective. None of them had characterized the spatial power distribution of the beam. In four out of five cases, the exposures fell outside the therapeutic photobiological window according to the parameters reported by the authors themselves: surface temperatures reaching 55 °C and locally 71 °C, coagulation and necrosis leading to paralysis and death of the animals, and irradiances approximately 25 times higher than clinical irradiances. The fifth study, a xenograft, used a dose within the therapeutic window but involved an immunodeficient host; a sixth study by the same group, using the same device at therapeutic irradiance, reported a benefit. Cronshaw M et al., Biomedicines (DOI 10.3390/biomedicines14081859)

In other words, some of the literature that fuels concerns about tumor stimulation actually describes burns. This does not settle the issue of oncological safety—which remains an open and legitimate question—but it does shift the burden of proof.

Clinically, a series of nine cancer patients with a culture-confirmed oral Pseudomonas aeruginosa infection showed complete resolution in all nine, with a median healing time of 5 days. The protocol combines antimicrobial photodynamic therapy, photobiomodulation, and systemic antibiotic therapy; the specific contribution of photobiomodulation cannot be isolated. Gobbi MF et al., Einstein São Paulo (DOI 10.31744/einstein_journal/2026AO2422)

Finally, four patients with multiple myeloma treated with talquetamab and receiving concomitant 660- and 808-nm photobiomodulation all developed dysgeusia—including two with complete ageusia—and xerostomia. There were no cases of oral mucositis, and no treatment discontinuations due to oral toxicity. Given that these were four uncontrolled cases, no conclusions regarding efficacy can be drawn, and the authors do not claim any such efficacy. Ferreira MH et al., Supportive Care in Cancer (DOI 10.1007/s00520-026-11133-8)

Let's review what remains unchanged: in oncology, photobiomodulation is used as supportive care and never as a treatment for the tumor.

Neurology and Cognition

The most citable publication of the summer in neurology is a Bayesian network meta-analysis of 35 randomized trials involving 1,559 patients with Alzheimer’s disease. It compares PBM, direct current transcranial stimulation, and repetitive transcranial magnetic stimulation. PBM showed the highest estimated effects on the MMSE (mean difference 3.14; 95% credible interval 1.71 to 4.60) and on the ADAS-Cog (-8.01; -12.82 to -3.13), with comparable feasibility and safety. Its superiority over rTMS is established only on the ADAS-Cog (-5.24; -10.23 to -0.12): on the MMSE, the comparison narrowly misses statistical significance (1.57; -0.02 to 3.18). The authors note that these effects are largely based on indirect comparisons (DOI).

In terms of mechanisms, a study published in *Brain* on APP/PS1 and 3xTg mice shows that PBM reduces cortical infiltration of CD8+ T cells and neuroinflammation—along with cognitive improvement—by inhibiting the microglial NLRP3 inflammasome and rebalancing the crosstalk between microglia, astrocytes, and T cells (DOI). In a sporadic Alzheimer’s-like model in rats, pulsed LED stimulation at 40 Hz reverses cognitive deficits, increases BDNF, and reduces caspase-3 (DOI).

Volume 189 of the *International Review of Neurobiology*, indexed in mid-August, devotes several chapters to the application of red and near-infrared light to the brain. Hamblin provides an overview of traumatic brain injury, from mitochondrial mechanisms to modulations of the default mode network observed via functional MRI (DOI). Johnstone and Gordon advocate for remote photobiomodulation, in which irradiating one area of the body produces benefits in distant tissues, analogous to remote ischemic conditioning (DOI). Dole compares transcranial PBM to other noninvasive neurostimulation techniques in cerebral aging and identifies the quantification of the energy that actually reaches the target as the main challenge (DOI). Valverde and his co-authors explore a new avenue in amyotrophic lateral sclerosis, highlighting the importance of early treatment (DOI).

An observational study should be read with its limitations in mind: seven patients with Parkinson’s disease used daily transcranial PBM for 6 to 34 months, most of them with homemade devices. Patients, spouses, and clinicians reported improvements in fatigue, sleep, apathy, mood, concentration, and sense of smell, with no adverse effects. There was no control group, and the length of follow-up does not compensate for this lack of a control group (DOI).

Regarding the spinal cord, two studies complement each other. A Raman spectroscopy analysis following spinal cord contusion in rats shows that 808-nm PBM administered over 14 days stabilizes the biochemical microenvironment upstream of the lesion, preserves protein integrity, and attenuates the lipid disruption associated with myelin degradation (DOI). And in *Advanced Science*, extracellular vesicles derived from microglia treated with 850-nm PBM are used to deliver UFL1: in rats, they reduce glial scarring and improve axonal regeneration and motor recovery (DOI). A review of clinical translation rounds out the picture by listing what is still missing: clear dosimetry, data from large animals, and a clinical-grade device (DOI).

The most comprehensive publication in neurology over the past two months is a Bayesian network meta-analysis on Alzheimer's disease: 6,450 references screened, 91 randomized trials included, 12,242 participants, and five interventions compared with one another. Photobiomodulation and repetitive transcranial magnetic stimulation were found to have significantly beneficial effects on cognitive function; pharmacotherapy and cognitive therapy on activities of daily living; and cognitive therapy and exercise on quality of life. An important caveat: the abstract provides no effect sizes, no credibility intervals, and no SUCRA rankings. Knowing that an effect is significant without knowing whether it is equivalent to two MMSE points or half a standard deviation does not allow for meaningful decision-making. Gao F et al., iScience (DOI 10.1016/j.isci.2026.117250)

Regarding spinal cord injury, a randomized study in rats yielded an unexpected result. Photobiomodulation at 660 nm and polyethylene glycol, when tested alone or in combination, produced better results in male rats as monotherapies than when used together. In females, photobiomodulation reduced apoptosis, and both monotherapies reduced microglial activation. The sex dimorphism was clear, which is rarely documented in this field. Mojarad N et al., Lasers in Medical Science (DOI 10.1007/s10103-026-05013-0)

A clinical review on the sequelae of stroke provides an overview of transcranial photobiomodulation for cognitive disorders and aphasia, and of peripheral photobiomodulation for spasticity and pain in the paretic limb. The authors conclude that there are positive signs but that clinical evidence remains limited. Ren C et al., Frontiers in Neurology (DOI 10.3389/fneur.2026.1859831)

Oral Health

This is the most extensively studied area for this period, and it includes the largest clinical cohort of the summer. A single-blind, randomized trial included 272 adults who received a single-tooth implant and underwent daily 810-nm diode laser irradiation for five postoperative days. LLLT reduced pain at all follow-up time points, by 0.35 to 1.21 points, and improved healing and bleeding indices. The crevice fluid contained persistently lower levels of TNF-α and higher levels of VEGF, and marginal bone loss was 0.07 to 0.22 mm less after the seventh day (DOI).

En pédiatrie, un essai en bouche divisée chez 18 enfants après extraction de molaires temporaires rapporte un score de cicatrisation supérieur à J7 (médiane 5,00 contre 4,00, p = 0,002) et surtout aucune prise d'antalgique dans le groupe PBM 660 nm contre 33,3 % sous placebo (DOI). Une étude prospective sur 24 patients après dépigmentation gingivale chirurgicale montre une surface résiduelle médiane deux fois plus faible à J7 sur les sites traités (0,35 contre 0,72 mm², p < 0,001), avec une épithélialisation complète partout à J15 (DOI).

A meta-analysis of 15 trials on oral lichen planus found a slight reduction in pain compared with conventional pharmacological treatment, with no effect on disease severity or anxiety. However, complete mucosal healing was more common, and recurrences were less frequent in erosive forms. No adverse effects were reported (DOI).

There are numerous negative results, and it would be dishonest to ignore them. A double-blind trial involving 36 patients who underwent endodontic surgery showed no difference in pain at 24 hours, analgesic use, bruising, or swelling, but significantly better soft-tissue healing at 7 days (p = 0.013) (DOI). A split-mouth pilot study involving 27 patients following aesthetic crown lengthening found no benefit from 660 nm PBM at 30 J, neither in terms of healing nor pain (DOI). A three-arm trial involving 90 patients following single-visit endodontic treatment found no difference between 940-nm PBM and intracanal cryotherapy compared to saline irrigation, with all groups achieving zero pain by day 7 (DOI). Finally, a split-mouth pilot study involving 6 periodontal patients found no change in plaque microbiota after six months of monthly PBM, which seriously limits claims regarding its antibacterial effects (DOI).

A rare comparison is worth noting: In 87 patients with cleft lip and palate, representing 104 graft sites, local PBM at 880 nm yielded 80% favorable Chelsea classes compared with 45% for the control group, whereas vascular PBM applied to the radial artery at 660 nm peaked at 37.5% and was indistinguishable from the control (DOI). Local irradiation remains a step ahead of systemic irradiation.

In orthodontics, an umbrella review of 20 systematic reviews concluded that there is evidence of low certainty regarding the acceleration of tooth movement, a slight reduction in root resorption, and short-term pain relief, with no recommendation for routine use (DOI). A review focused on aligners reports average treatment durations of 528 days with PBM versus 719 days in the control group—a 26.6% reduction—using wavelengths ranging from 780 to 830 nm, with no difference in root volume on CBCT scans (DOI). A split-mouth trial involving 96 patients shows that at a constant energy of 60 J, a pulsed setting at 15 Hz provides the best analgesia, and that frequency and analgesic effect are not linearly correlated (DOI). A systematic review of 5 trials and 178 mini-implants found favorable evidence regarding stability in 3 out of 5 studies, with wave lengths ranging from 618 to 940 nm (DOI).

It is also worth noting a four-arm trial involving 72 patients that compared PBM alone, PRF, a combination of the two, and a control group for alveolar preservation, using precisely reported doses of 2 and 6 J/cm², making this a reproducible protocol (DOI).

A randomized, sham-controlled trial compared 660 nm at 17.26 J/cm² and 808 nm at 33.16 J/cm² on the S100A8/A9 inflammatory marker in symptomatic irreversible pulpitis. The increases observed with photobiomodulation were numerically higher than those with sham treatment, particularly at 660 nm in older patients, but did not reach statistical significance. With 14, 13, and 8 patients per arm, the trial lacked the necessary statistical power anyway. Zhu M et al., Lasers in Medical Science (DOI 10.1007/s10103-026-05006-z)

In gingival and periodontal fibroblasts from patients with poorly controlled diabetes (HbA1c greater than 8), a 940-nm diode laser at 0.1 W exhibits a counterintuitive dose-response profile: viability is significantly higher after three exposures at 4 J, but only in gingival fibroblasts, whereas proliferation is better at 2 J in both cell types. In vitro wound healing is accelerated at 12 and 24 hours in all irradiated groups. Bakshi PV et al., Journal of the Indian Society of Periodontology (DOI 10.4103/jisp.jisp_18_25)

In a study using stem cells from shed deciduous teeth, a comparison between 660 nm at 25 mW and 940 nm at 100 mW, at 1 and 2 J/cm², showed an advantage for near-infrared light: the 940 nm treatment increased proliferation at 24 and 72 hours and remained the only treatment significantly superior to the control at 72 hours. At 24 hours, all irradiated groups showed improved viability except for the 660 nm group at 2 J/cm². Rahimpour S et al., Frontiers in Dentistry (DOI 10.18502/fid.v23i7.21236)

Finally, a study on root dentin conditioning shows that all tested wavelengths increase the release of TGF-beta 1 compared to the negative control, with a maximum observed for the pulsed Nd:YAG laser at 60 J/cm², and a significantly increased alkaline phosphatase activity at 7 days, without cytotoxicity. This study lies at the intersection of photobiomodulation and surface conditioning. Mokhtari H et al., Lasers in Medical Science (DOI 10.1007/s10103-026-04971-9)

Wound Healing and Chronic Wounds

In early August, the British Journal of Nursing published a three-part series on evidence-based practice in wound care: an article on parameters and safety (DOI), a mechanistic review on the modulation of reactive oxygen species and the displacement of nitric oxide from cytochrome c oxidase (DOI), and a series of four case reports covering hard-to-heal leg ulcers and radiation-induced fibrosis, with follow-up periods of up to 19 months (DOI). A disclosure: the author of the first article is the scientific director of a PBM device manufacturer.

Regarding diabetic foot ulcers, a prospective observational study conducted at a public hospital in Rio de Janeiro followed 11 patients and 15 ulcers. In the LLLT group, 5 out of 9 ulcers healed completely and 4 improved without worsening, compared with 1 complete healing out of 6 in the conventional treatment group. The observational design and sample size preclude any causal inference, but real-world data remain scarce for this indication (DOI). A randomized trial involving 40 patients is also testing hyperbaric oxygen therapy followed by polarized light therapy for neuropathic foot ulcers (DOI), and a Brazilian protocol will evaluate the combination of a Terminalia fagifolia extract and 904 nm GaAs PBM at 10 J/cm² in 102 patients (DOI).

In bone regeneration, a calvarial defect model in 30 rats showed a clear additive effect: at 42 days, bone formation reached 26.64% with the biomaterial, fibrin, and 830-nm PBM, compared to 20.05% without PBM and 14.85% with the biomaterial alone, with a transition to a mature lamellar architecture (DOI).

On the cornea, 830-nm PBM administered every 12 hours following an alkaline burn in rats accelerates epithelial closure, reduces corneal opacity at one week (p = 0.029), causes a drop in IL-1β, IL-6, and TNF-α at 48 hours, and increases the expression of the Rho-GTPases RhoA and RhoC in the early phase (DOI).

Two separate studies. A vascular coating that releases nitric oxide under red light reduces intimal hyperplasia after balloon angioplasty more effectively than PBM alone (DOI). And a veterinary trial with intra-wound controls in 15 dogs and cats found no significant difference in the effects of fluorescence biomodulation on lesion size reduction, histology, or angiogenesis: a reminder that not all light-based technologies are created equal and that they must be distinguished from one another (DOI).

Finally, a clinical practice article describes the use of red and near-infrared PBM for nipple trauma and inflammatory conditions of the lactating breast, featuring an innovation led by two lactation consultant nurses in Ireland (DOI). A Brazilian double-blind pilot trial involving 58 postpartum women confirms the feasibility of a larger-scale trial for this indication, though no efficacy results are available at this stage (DOI).

A critical integrative review on chronic wounds offers a range of parameters worth noting, because it is rarely stated so explicitly: 450 to 950 nm, 2 to 20 J/cm², 10 to 500 mW/cm², in continuous, pulsed, or superpulsed modes. Yadav D, Gupta A, Biochemistry (DOI 10.1016/j.biochi.2026.08.017)

A negative result was observed in plastic surgery. Thirty-one patients who underwent abdominoplasty, non-randomly assigned to the PBM group (n = 15) and the control group without sham treatment (n = 16), received a single session of 808-nm laser therapy at 100 mW and 3 J per point prior to discharge: neither TNF-alpha, nor IL-10, nor salivary nitrites, nor pain scores showed any change. The only observed variation—a decrease in TBARS at 48 hours—disappeared after adjustment. A single session following major surgery was likely too low a dose to expect any effect. Araujo CLK et al., Lasers in Medical Science (DOI 10.1007/s10103-026-05007-y)

Dermatology and Aesthetics

A three-round Latin American Delphi consensus, involving 22 dermatologists and covering 23 clinical scenarios involving keloids and hypertrophic scars, identifies low-level phototherapy as one of the first-line treatment options for early-stage and inflammatory scars in populations with high phototypes, and systematically favors combination therapies (DOI). This represents formal recognition within a treatment algorithm, even though no specific parameters are specified.

From a mechanistic perspective, red light at 650 nm applied after UVA exposure partially restores the viability of human dermal fibroblasts, increases the expression of type I collagen, and reduces apoptosis (DOI). In *Advanced Materials*, a flexible patch that converts ambient light into red light promotes fibroblast proliferation and wound healing without an external light source; a study on facial skin showed improved viscoelastic recovery after a single session (DOI).

A clinical case report describes improvement in androgenetic alopecia with fibrosis that was resistant to treatment with low-intensity phototherapy administered at home; the PubMed abstract does not provide any figures (DOI). A review of light-based devices for acne indicates that PBM offers moderate benefit in mild cases (DOI). A methodological framework linking laser physics to clinical criteria based on the Fitzpatrick phototype usefully complements practitioners’ toolkit (DOI).

Ophthalmology

The strongest health economic argument of the summer comes from a 24-month cost-effectiveness analysis of LIGHTSITE III, from the perspective of U.S. payers. The incremental cost-effectiveness ratio is $73,910 per QALY, below the $100,000 and $150,000 thresholds, driven by a 71.7% relative reduction in incident geographic atrophy (DOI).

In children, a meta-analysis of 18 articles and 2,438 participants confirms that repeated low-level red light reduces axial length by an average of 0.26 mm (95% CI -0.34 to -0.18) and slows refractive progression by 0.60 D (95% CI 0.42 to 0.78), with very high heterogeneity (I² > 97%) (DOI). A retrospective study of 158 children compares it to posterior scleral reinforcement in high and very high myopia (DOI), and a systematic review identifies 45 pediatric studies ranging from 400 to 1,100 nm, primarily focused on myopia control (DOI).

These figures should be interpreted in light of the accompanying safety warnings. JAMA Ophthalmology reports the occurrence of subretinal fluid following repeated red light exposure (DOI). A review of efficacy and safety notes transient foveal hyperreflectivity, cystoid abnormalities on OCT, and changes on the multifocal electroretinogram, with no irreversible damage reported to date, and calls for long-term follow-up (DOI). A narrative review on pre-myopia explicitly recommends caution in children until the safety profile is better established (DOI). We see no reason to soften this message.

In a double-blind, randomized trial involving 58 patients, LLLT combined with intense pulsed light was shown to produce a sustained increase in lipid film thickness—an additional 10.3 nm at 24 weeks—without providing any greater symptomatic benefit (DOI). A measurable structural effect does not always translate into a perceived improvement.

Le résultat le plus net de la période en ophtalmologie vient de Chine. Il ne s'agit pas d'un essai randomisé, mais d'une étude comparative avec appariement par score de propension. Une équipe y a inclus 216 enfants de 7 à 12 ans non encore myopes, dont 192 ont terminé les douze mois de suivi, répartis entre lumière rouge répétée de faible intensité et atropine à 0,01 %. Les pourcentages qui suivent portent sur ces 192 enfants. Les deux bras reçoivent donc un traitement destiné à empêcher l'apparition de la myopie, l'atropine à faible dose étant aujourd'hui la référence. À un an, 13,3 % des enfants sous lumière rouge ont déclaré une myopie, contre 30,7 % sous atropine, soit 17,4 points de moins (IC95% 5,2 à 28,1 ; p = 0,028) en faveur de la lumière rouge. Après appariement de 69 paires, l'écart reste identique (11,6 % contre 29,0 % ; p = 0,038). L'équivalent sphérique progresse de +0,08 D contre -0,49 D (différence -0,57 D ; p < 0,001) et la longueur axiale de 0,02 mm contre 0,29 mm (p < 0,001). Aucun effet indésirable n'a été rapporté sous lumière rouge, contre 19,7 % de photophobie sous atropine. Ma X et al., Photodiagnosis and Photodynamic Therapy (DOI 10.1016/j.pdpdt.2026.105624)

This is not a randomized trial, and propensity score matching is not a substitute for randomization. The reservation regarding long-term retinal safety in children, as noted above, remains valid.

Côté surface oculaire, une cohorte rétrospective de 20 femmes ménopausées atteintes de sécheresse oculaire modérée a utilisé un masque LED du commerce, 20 minutes un jour sur deux pendant trois semaines. L'osmolarité lacrymale (p < 0,001), le temps de rupture du film lacrymal (p = 0,001) et le score OSDI (p < 0,001) s'améliorent ; le test de Schirmer, lui, ne bouge pas (p = 0,29). Vingt patientes sans groupe témoin, cela reste un signal, pas une preuve. Scuderi L et al., International Ophthalmology (DOI 10.1007/s10792-026-04219-z)

A narrative review on photoreceptor preservation also highlights the only definitive regulatory development in this field: the De Novo authorization granted by the FDA in 2024 for the Valeda system for dry AMD. Toro MD et al., Antioxidants (DOI 10.3390/antiox15081034) Conversely, a review of pachychoroidal pathologies concludes that current evidence does not support the routine use of photobiomodulation in this spectrum. Kayabasi M et al. (DOI 10.51329/mehdiophthal1544)

Sports, Recovery, and Cellular Mechanisms

Two studies cast doubt on the promises of performance gains. A meta-analysis of 11 randomized trials concludes that PBM added to resistance training in older adults does not significantly improve maximum strength (SMD 0.26, not significant), while leaving open the question of recovery and fatigue in frail populations (DOI). A placebo-controlled trial involving 30 healthy adults, using 830 nm and 300 J per limb, found no overall effect on ankle proprioception after fatigue; only an exploratory interaction suggested a benefit in subjects with high perceived instability (DOI).

A letter commenting on the trial by Costa and colleagues on hard-to-control asthma sums up the situation well: the combination of resistance training and PBM improves peripheral strength and exercise capacity, but not lung function or asthma control, and the trial did not include a PBM-only arm (DOI).

In preclinical studies, a controlled trial in 16 rabbits with bupivacaine-induced myonecrosis showed lower dystrophy scores in the 810-nm laser group (p = 0.039), reduced inflammatory infiltration on Day 6 (p = 0.011), and significantly lower serum creatine kinase levels on Day 3 (1,560 vs. 4,500 IU/L) and Day 6 (1,090 vs. 3,043 IU/L), with the appearance of central myonuclei observed only in the treated group (DOI).

Two in-depth reviews provide context for the mechanistic discourse. A review in the *Journal of Photochemistry and Photobiology B* discusses the absorption of photons between 600 and 1,100 nm by cytochrome c oxidase, the increase in ATP, and the regulation of the PI3K/Akt, MAPK, and NF-κB pathways, emphasizing the bidirectional, dose-dependent nature of these effects and the need for standardization (DOI). A cross-disciplinary review in *Annals of Translational Medicine* explicitly distinguishes between validated clinical applications, exploratory findings, and preclinical research, and presents mitochondrial activation as a proposed mechanism whose centrality likely depends on the modality and context (DOI). We believe this nuance is important: mitochondria explain a great deal, but they do not explain everything.

Chow and Armati offer the most comprehensive explanation of the direct analgesic effect, identifying the initial segment of the axon—the site where the action potential originates—as the likely target of PBM on neurons in the spinal ganglia and the trigeminal ganglion (DOI). In human endothelial cells, 660 nm PBM increases proliferative activity, with a maximal effect at 7.5 J/cm² and viability greater than 95% (DOI). In stimulated macrophages, the combination of 780 nm PBM and 2 µM dexamethasone further reduces TNF-α and IL-6 compared to dexamethasone alone, while the 4 µM dose proves less effective: a potential strategy for reducing corticosteroid use that warrants further investigation (DOI).

Le résultat le plus dérangeant de la période vient des Pays-Bas. Douze sujets sains de 25 ans en moyenne ont reçu sur une jambe une séance unique de photobiomodulation, soit trois cycles de 5 minutes 16 secondes délivrant 5,6 kJ chacun, l'autre jambe servant de sham chez le même participant. La température cutanée monte bien dans la jambe traitée, de 8,0 ± 1,4 °C (p < 0,001) : la lumière a donc été délivrée. Mais la respiration mitochondriale maximale couplée aux complexes I et II ne diffère ni dans la peau (2,7 ± 0,8 contre 2,6 ± 0,7 pmol/s/mg de poids humide ; p = 0,66) ni dans le muscle (474 ± 114 contre 467 ± 81 pmol/s/mg de poids sec ; p = 0,71). La sensibilité mitochondriale à l'ADP ne bouge pas non plus (p = 0,14), et sur 91 gènes analysés, 3 seulement diffèrent entre les deux jambes. Aussieker T et al., Medicine and Science in Sports and Exercise (DOI 10.1249/MSS.0000000000004120)

Three limitations should be kept in mind when interpreting this result. The authors themselves note the first two in their conclusion: this was a single session, whereas a chamber is typically used for repeated sessions, and the measurement was performed ex vivo on permeabilized muscle fibers and ground skin, which by design eliminates any effects mediated by circulation or a systemic response. The third limitation relates to the interpretation: the participants were young and healthy, and thus had little room for mitochondrial improvement. Furthermore, the abstract provides neither wavelength nor irradiance, only the total energy, which makes it impossible to verify that the protocol fell within the therapeutic window.

What the study establishes is therefore precise and limited: a single exposure does not produce an acute increase in mitochondrial respiration in healthy young subjects, based on tissue samples. It says nothing about adaptation following several weeks of training sessions. Nevertheless, this is enough to undermine the reflexive use of cytochrome c oxidase as a universal explanation: just because a mechanism is cited everywhere does not mean it has been demonstrated everywhere.

From a dosimetric standpoint, a finite-element simulation using an anatomically realistic head model with millimeter-scale resolution yields a figure that puts things into perspective: approximately 0.05% of the incident optical power reaches the cortical gray matter. As power density increases, scalp temperature rises to 5.22 °C and brain temperature to 0.49 °C, with a halo diffusion effect in the cerebrospinal fluid. Skin thermal stress therefore occurs well before cerebral thermal stress, which mechanically limits the doses that can be delivered transcranially. Liu X et al., Sheng Wu Yi Xue Gong Cheng Xue Za Zhi (DOI 10.7507/1001-5515.202512019)

From an immunological perspective, an 808-nm laser applied in vitro to human NK cells and in vivo in mice at 10 J/cm² for 60 seconds, every other day for two weeks, increases intracellular ROS and ATP, enhances NK cytotoxicity with NKG2D overexpression, and lowers serum CXCL1 and IL-12p40 levels. No p-values are provided. Huyan T et al., Lasers in Surgery and Medicine (DOI 10.1002/lsm.70176)

Emerging Findings and Tools

A three-arm randomized trial in postmenopausal women compared PBM combined with pelvic floor muscle training to sham PBM and pelvic floor muscle training alone, over 16 sessions. Manometry did not show a significant difference between the groups, but the total score on the Female Sexual Function Index was significantly higher with active PBM compared to sham PBM (mean difference 4.55, 95% CI 0.57 to 8.52), with a clinically significant improvement of 3.06 points on the ICIQ-SF (DOI).

In diabetic rats, 808-nm PBM applied to the renal region three times a week for six weeks improves inulin clearance, reduces albuminuria and serum creatinine, increases renal blood flow, and lowers mean arterial pressure, with no significant histological differences (DOI). Two girls with Hinman syndrome treated with 630 nm red LED light in the suprapubic region saw their post-void residual urine volumes decrease by 93.6% and 59.6%, respectively; these two cases, for which no dose was reported, should be treated as an exploratory finding (DOI).

A meta-analysis of 6 trials and 386 participants found a reduction in anxiety symptoms with laser auriculotherapy (SMD -0.65, 95% CI -1.17 to -0.13), but the effect disappears when studies at high risk of bias are excluded (SMD -0.35, 95% CI -0.94 to 0.25), and the certainty of the evidence is very low to low (DOI). Interpret these findings with caution.

Finally, two tools. In PNAS, a digital twin built from real human CT scans models pulmonary light dosimetry using 12 tissue types and shows significant variations in energy deposition depending on the condition of the lung: a case for individualized dosimetry rather than fixed protocols (DOI). And a validated self-assessment battery for transcranial PBM identifies response moderators, ranging from skin phototype to capillary properties, sleep, and nicotine; its authors are affiliated with a headset manufacturer, which is important to know before using it (DOI).

A prospective, single-arm study of patients with type 2 diabetes taking metformin reports, following vascular photobiomodulation of the radial artery, acute decreases in capillary blood glucose levels after each session (from over 180 to 220 mg/dL to 119 to 129 mg/dL; p ≤ 0.0019) and a decrease in fasting blood glucose levels over six weeks, from 161.40 to 130.40 mg/dL (p = 0.0339). HbA1c, however, remained unchanged (7.61% vs. 7.65%), and this is the key measure. Without a control group, these results remain exploratory. Almeida LA et al., Lasers in Surgery and Medicine (DOI 10.1002/lsm.70192)

La médecine vétérinaire a livré deux essais contrôlés peu concluants. Sur 16 chiens militaires randomisés en photobiomodulation contre sham pour des plaies caudales, la surface de plaie n'évolue significativement dans aucun des deux groupes (PBM 0,6 ± 0,4 à 0,7 ± 0,4 cm² ; sham 1,3 ± 1,0 à 1,1 ± 0,7 cm²). La zone glabre péri-lésionnelle diminue dans les deux bras, sans différence entre eux (p = 0,077). L'imagerie thermique montrait par ailleurs un lit de plaie plus chaud que le tissu voisin (delta 2,8 ± 0,7 °C ; p < 0,001), signe d'une perfusion conservée, et non un contrôle de la dose délivrée. Fishelson Y et al., The Veterinary Journal (DOI 10.1016/j.tvjl.2026.106838) Un essai de terrain sur 129 vaches laitières en mastite subclinique ne trouve d'avantage au laser froid que chez les vaches à mastite aiguë contagieuse, sans effet significatif sur la récupération, la production laitière ni la survie. Shrestha B et al., Frontiers in Veterinary Science (DOI 10.3389/fvets.2026.1856042)

A prospective, multicenter pilot study involving 22 dogs and 38 ears with otitis externa reported, after five sessions of dual-wavelength infrared photobiomodulation, a median pruritus score decreasing from 5.5 to 2 cm on a visual scale and a prevalence of foul odor decreasing from 94% to 54%. Cytology showed a decrease in yeast and keratinocyte scores, while microbiological cultures did not vary significantly. No p-values are provided, there is no control group, and the authors conclude that there is an association rather than efficacy. Gesuete F et al., Animals (DOI 10.3390/ani16152372)

For the record, a bibliometric analysis of 4,907 publications between 2006 and 2025 estimates the field’s annual growth rate at 14.67 percent, ranks Michael R. Hamblin as the top author, and places Brazil at the top among publishing countries with 32.2 percent of the total (DOI).

Frequently Asked Questions

Does a higher dose of photobiomodulation produce better results?

No, and the studies conducted in July and August 2026 demonstrate this in several ways. In humans, moderate irradiance increases the BOLD signal in the brain, whereas low irradiance decreases it. In cell culture, 9 J provides protection, 30 J provides partial protection, and 60 J exacerbates oxidative stress. Photobiomodulation operates within a therapeutic window, not according to a logic of increasing dose.

Which indications for PBM are best established today?

The prevention of oral mucositis in patients undergoing cancer treatment remains the most well-established application, as confirmed this summer by the POMFITT trial, which showed a 0% rate of severe mucositis compared to 26.6% with standard care. Next come postoperative pain in implantology and mucogingival surgery, musculoskeletal rehabilitation, and the healing of chronic wounds.

Is red light safe for children's eyes?

Its effectiveness in controlling myopia has been documented, with an average reduction in axial length of 0.26 mm. However, several studies published this summer report transient retinal abnormalities and one case of subretinal fluid. No irreversible damage has been reported to date, and the authors recommend caution and regular ophthalmologic follow-up for children.

How does photobiomodulation affect cells?

The most commonly cited explanation is mitochondrial: red and near-infrared light is thought to be absorbed by cytochrome c oxidase, which boosts ATP production. A recent study casts doubt on this theory. In 12 young, healthy subjects, with one leg treated and the other receiving a sham treatment, mitochondrial respiration measured ex vivo on muscle and skin biopsies did not differ between the two legs, even though light was indeed delivered. However, the limitations of this study should be noted: it involved a single session and an acute measurement, not a protocol repeated over several weeks. The clinical effects observed elsewhere do not disappear, but the mechanism requires further clarification.

Does photobiomodulation improve muscle strength?

Summer data suggests that PBM does not increase maximum strength. A meta-analysis of 11 trials involving older adults found no significant improvement in 1RM when PBM was added to resistance training. PBM remains of interest for recovery and fatigue, but not for strength gains.

Key Takeaways

Three publications have raised the level of evidence over these two months: the network meta-analysis showing that PBM is superior to rTMS in Alzheimer’s disease, the randomized trial involving 272 patients in implantology, and the POMFITT trial on oral mucositis. The cost-effectiveness analysis from LIGHTSITE III adds another, economic, argument to the mix, which will carry weight in treatment decisions.

The rest of the period tells a more sober and practical story. There are numerous negative studies, many of which are well-conducted: myofascial pain in the trapezius, coronary elongation, periodontal microbiota, ankle proprioception, and maximum strength in older adults. Far from weakening the field, they help define its boundaries. A technology that fails in one area is a technology that can be taken seriously in another.

And the common thread can be summed up in one sentence: what distinguishes an effective protocol from a useless one is not the power of the device, but the settings—wavelength, irradiance, energy per spot, and number of sessions. As long as these parameters remain so inconsistent from one study to another, meta-analyses will continue to conclude that there is insufficient evidence for indications where PBM is, in fact, effective.

Two studies stand out from the rest, pointing in opposite directions. The prevention of childhood myopia through repeated red light exposure has become the best-documented indication in the field, with broad and consistent differences across all criteria—incidence, refraction, and axial length. Meanwhile, the mitochondrial hypothesis has just suffered a serious setback in human muscle.

One final point is worth noting, because it changes the way we interpret the older literature. A dosimetric reanalysis shows that some of the studies used to document the dangers of this method in oncology actually described exposures at 55 or even 71 degrees, resulting in necrosis. These were burns, therefore, and not photobiomodulation at clinical parameters. The question of safety in oncology remains open, but it must be reexamined on a sound foundation.

To learn more about our devices and our approach to photobiomodulation, visit bioledtherapy.com.

Sources: PubMed / NCBI. The DOI links lead to the original publications. The abstracts are indicative summaries; please refer to the full text before any clinical application or dissemination. Photobiomodulation is not a substitute for prescribed treatment; consult a healthcare professional.