Photobiomodulation: Studies from September 2026

A busy September, with trials pitting active treatments against one another

September 2026 was a busy month for research on photobiomodulation (PBM).

Between September 1 and October 4, 101 references were retrieved from PubMed for the search term “photobiomodulation.” After excluding articles that actually dealt with ablative, vascular, or hair removal lasers, as well as those on IPL, an errata, and a few reviews in which PBM was only mentioned in passing, 85 studies are cited here, each with its DOI link.

Profile of the Month: 18 systematic reviews or meta-analyses, 12 randomized trials, 7 non-randomized clinical trials, 3 protocols, and a body of basic research (11 animal studies, 8 in vitro studies). Neurology, dentistry, and mechanistic research account for more than half of the articles.

A common thread runs through this period: several studies no longer compare light therapy to a placebo but to an active treatment. Celecoxib before knee replacement surgery, ultrasound for knee osteoarthritis, mirror therapy after a stroke, and selenium and vitamin D for autoimmune thyroiditis. This is the question practitioners are asking, and it’s good news that the literature is beginning to provide answers.

Four negative or neutral studies are grouped together in a dedicated section. We see no reason to hide them: they define the scope of the research just as much as the positive results do.

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

Table of Contents

• Pain and the Musculoskeletal System
• Oral Health
• Oncology and supportive care
• Neurology and Mental Health
• Ophthalmology
• Sports, Recovery, and Performance
• Wound Healing and Dermatology
• Emerging Indications
• Mechanisms and Basic Research
• Negative or neutral results
• Frequently Asked Questions
• Key Takeaways

Pain and the Musculoskeletal System

The most notable finding of the month comes from the field of orthopedic surgery. A double-blind, double-placebo non-inferiority trial published in *Frontiers in Cell and Developmental Biology* compared, in 80 patients who underwent total knee replacement surgery, a preoperative session of 810-nm laser PBM with celecoxib as preemptive analgesia. Resting pain at 24 hours was 3.9 ± 1.1 with PBM versus 3.7 ± 1.0 with the anti-inflammatory drug, a difference of 0.20 points (95% CI -0.27 to 0.67), with the upper bound remaining below the non-inferiority margin set at 1 point. The WOMAC score at 48 hours did not differ (42.4 vs. 41.8; p = 0.655). The PBM group, however, had less thigh swelling on days 3 and 7, less occult blood loss, and less gastrointestinal discomfort (DOI).

Dans la gonarthrose, un essai randomisé monocentrique en aveugle de l'évaluateur a opposé chez 66 adultes la laserthérapie de haute intensité (HILT) aux ultrasons, deux fois par semaine pendant 6 semaines, en complément d'exercices. En intention de traiter, la réduction du WOMAC total à 12 semaines après traitement atteignait 40,0 points avec la HILT contre 8,2 avec les ultrasons (différence ajustée -27,7 ; IC 95 % -39,0 à -16,5 ; p < 0,001), avec un maintien des effets jusqu'à 12 semaines alors que le groupe ultrasons perdait progressivement ses gains (DOI). Une méta-analyse de 105 études (2 710 patients traités, 2 925 contrôles) consacrée à la HILT, lasers de classe IV entre 0,5 et 80 W, rapporte des réductions durables de la douleur (SMD -0,98 en fin de traitement, -1,18 avant 3 mois, -1,01 au-delà) et une supériorité sur la LLLT dans les 13 essais comparatifs disponibles, sans événement indésirable grave. L'un des auteurs est affilié à un fabricant de lasers, ce qui invite à lire ces conclusions avec prudence (DOI).

Pour les lésions méniscales confirmées par IRM, un essai randomisé en double aveugle contre placebo chez 40 adultes montre que la LLLT ajoutée à 6 semaines de rééducation standardisée améliore davantage la douleur, le score de Lysholm, la mobilité et les amplitudes articulaires que le placebo (p < 0,01 pour tous les critères), en dépassant les seuils cliniquement significatifs ; les valeurs absolues ne sont pas données dans le résumé (DOI). Dans le syndrome douloureux régional complexe de type I après AVC, un essai randomisé (47 inclus, 44 analysés) a comparé LLLT et thérapie par miroir, chacune ajoutée à la kinésithérapie. Les deux groupes progressent à tous les suivis (p < 0,001) ; la LLLT fait mieux à 4 semaines sur la douleur (p = 0,039) et la récupération sensorimotrice (p = 0,022), sans différence à 8 et 12 semaines (DOI).

Regarding the shoulder, a meta-analysis of 21 randomized trials (1 , 118 patients) on subacromial impingement found a modest reduction in pain (MD -0.54; 95% CI -1.05 to -0.02; p = 0.04) and gains of a few degrees in flexion (+4.35°), abduction (+3.72°), and external rotation (+1.96°), with no effect on extension, internal rotation, or functional disability. The quality of evidence is rated as low to very low, and the authors suggest reassessing the value of continuing treatment beyond 12 sessions (DOI). A scoping review on auricular PBM, or laser auriculotherapy, identified 7 trials: positive trends were observed for chronic low back pain and temporomandibular disorders, with no significant differences for acute postoperative pain or knee osteoarthritis. The protocols used wavelengths of 808 to 904 nm or 650 to 660 nm, energy densities of 0.54 to 4 J/cm², and 8 to 10 sessions; the Shen Men point was stimulated in 85.7% of the studies (DOI). A commentary also discusses the meta-analysis by Alayat et al. on patellofemoral syndrome (DOI).

En douleur postopératoire ORL, un essai contrôlé chez 128 patients opérés d'une tympanomastoïdectomie a ajouté au traitement médicamenteux dix séances quotidiennes de laser 980 nm (50 mW, 8 J/cm², 8 points rétro-auriculaires). Les scores EVA étaient significativement plus bas dans le groupe PBM à tous les temps de mesure, avec une très grande taille d'effet à la cinquième séance, à 1 mois et à 3 mois, et des scores d'incapacité liés aux céphalées également inférieurs (p < 0,001) ; en revanche, aucun effet immédiat n'a été observé après la première séance (DOI). Une mini-revue dans Frontiers in Pain Research rappelle enfin que la longueur d'onde ne fait pas tout : la lumière verte perçue par la rétine est antinociceptive, la lumière rouge perçue visuellement est plutôt associée à une douleur accrue, alors que la LED rouge ou proche infrarouge appliquée localement réduit la douleur via la signalisation opioïde périphérique et le NO. La voie d'exposition, la dose et le moment comptent autant que la couleur (DOI).

En préclinique, une étude chez 12 lapins avec lésion partielle du tendon d'Achille a associé une LLLT 830 nm (15 mW, 3 J/cm²) à des exosomes de cellules souches adipeuses. À J21, la force de flexion et de dorsiflexion ainsi que la déformation du tendon et du muscle étaient significativement meilleures dans le groupe combiné (p < 0,05), avec des fibres de collagène compactes et parallèles à l'histologie (DOI). Ces résultats intéressent directement les kinésithérapeutes et centres de rééducation équipés en photobiomodulation corps entier.

Oral Health

L'implantologie bénéficie d'une méta-analyse de 32 essais randomisés (829 patients, 1 278 implants) publiée dans Dentistry Journal. La PBM réduit la douleur postopératoire (DM -0,27 ; IC 95 % -0,35 à -0,19), améliore la stabilité précoce mesurée au Periotest (DM -0,55) et en analyse de fréquence de résonance (ISQ +1,26 ; IC 95 % 0,61 à 1,91 ; p < 0,001) et limite légèrement la perte osseuse marginale (DM -0,09 mm ; IC 95 % -0,16 à -0,01). La densité osseuse initiale en CBCT était supérieure (DM 114,07 HU ; p = 0,01). La certitude GRADE reste faible à très faible (DOI).

Après extraction de troisième molaire mandibulaire incluse, deux travaux convergent. Un essai randomisé chez 70 patients (âge moyen 22 ans) montre qu'une seule séance extra-orale bi-longueur d'onde (650 + 904 nm, 10 min) abaisse la douleur EVA à J2 (20,3 ± 24,4 contre 41,4 ± 25,2 ; p < 0,001) et améliore la qualité de vie (69,8 contre 50,5 ; p = 0,002), sans effet sur l'œdème ni le trismus ; à J7 la différence persiste mais devient cliniquement négligeable (2,6 mm) (DOI). Une revue systématique de 8 essais, avec méta-analyse sur 2, confirme la réduction de la douleur à 24 h (SMD -0,64 ; IC 95 % -0,90 à -0,38), 48 h (SMD -0,82) et 72 h (SMD -1,11), sur un nombre limité d'études aux protocoles hétérogènes (DOI).

Dans le syndrome de la bouche brûlante, une méta-analyse de 18 essais randomisés rapporte une baisse de la douleur (DM -1,09 ; IC 95 % -1,60 à -0,57 ; I² = 89 %) et une amélioration de la qualité de vie orale OHIP-14 (DM -3,82 ; IC 95 % -4,79 à -2,86), sans effet net sur la xérostomie ni la dépression ; les analyses par paramètres d'irradiation restent exploratoires et ne permettent pas de définir un protocole optimal (DOI). Pour l'hypersensibilité dentinaire, une méta-analyse de 31 essais randomisés (25 en synthèse quantitative) place les thérapies laser en tête des modalités avancées, devant la nano-hydroxyapatite et le verre bioactif, avec un SMD poolé toutes modalités de -1,02 (IC 95 % -1,32 à -0,73 ; p < 0,001) (DOI). Une revue de cadrage sur 25 études (2010-2025) complète le tableau : diodes basse puissance de 630 à 980 nm, Er:Cr:YSGG et Nd:YAG sont efficaces, et l'association à un agent désensibilisant donne l'effet le plus rapide et le plus stable (DOI).

Un essai randomisé chez 24 patients avec dysfonction du nerf facial après chirurgie de l'articulation temporo-mandibulaire a comparé deux systèmes de PBM sur 15 séances et 60 jours. Les deux groupes s'améliorent sur les scores Sunnybrook et FaCE (p < 0,001) sans différence des grades House-Brackmann ; les variations J5-J60 favorisaient l'un des appareils pour Sunnybrook (17,67 contre 13,75 ; p = 0,036) et FaCE (22,92 contre 18,64 ; p = 0,040), mais le modèle mixte ne montrait pas de différence de trajectoire (DOI).

Several reviews call for caution. For temporomandibular disorders, a methodological review of 14 trials (620 patients) comparing PBM and TENS notes numerically greater improvements with PBM in terms of pain and mouth opening, but 12 of the 14 studies are Level III, and the heterogeneity precludes any conclusion of superiority (DOI). Regarding the prevention of cold sore recurrences, only 3 randomized trials exist: two report fewer recurrences after PBM, one finds no difference, and the certainty is low (DOI). In children with molar-incisor hypomineralization, a review of 8 trials on pain management during treatment found the results of PBM to be inconsistent across studies, with a high risk of bias in most trials (DOI).

Six publications round out this area. A review of the literature from the past ten years on neurosensory recovery of the inferior alveolar nerve following iatrogenic trauma (orthognathic surgery, implants, extractions) concludes that PBM accelerates nerve recovery and improves oral quality of life, using standard parameters of 630 to 1064 nm and 3 to 12 J/cm², but laments the lack of standardization (DOI). A systematic review of 8 studies on the combination of PBM and photodynamic therapy in dentistry (mucositis, orthodontics, endodontics, oral lesions) reports superior antimicrobial activity and wound healing compared to each modality alone, across heterogeneous protocols (DOI). A series of 5 cases of osteonecrosis of the jaws (radiation-induced, spontaneous, or drug-induced, with lesions smaller than 1 cm) treated with PBM (1 to 3 J, red or infrared) and photodynamic therapy using methylene blue describes favorable clinical responses, either alone or as an adjunct to minimal surgery; five cases do not allow for any generalizations (DOI). A narrative review of non-pharmacological treatments for the continuum from oral lichen planus to oral squamous cell carcinoma concludes that the strongest and most consistent evidence supports PBM for lichen planus and as supportive care for the toxicities of anticancer treatments (DOI). A scoping review on mesenchymal stem cells in regenerative dentistry describes how PBM increases proliferation, migration, and osteogenic, chondrogenic, and angiogenic differentiation depending on wavelength and dose, via cytochrome c oxidase, ATP, and the regulation of RUNX2, Sox9, and PPARγ (DOI). A case report describes the excision of a labial mucocele using an 810/980 nm superpulsed diode laser followed by postoperative PBM (0.3 W, 2 J per spot), resulting in healing without pain, edema, or recurrence at 90 days; the primary treatment remains surgical (DOI). Finally, a two-phase randomized trial protocol in children aged 10 to 13 aims to validate an extraoral condyle-localization device to guide LLLT in the orthopedic treatment of skeletal Class II malocclusions; Phase 2 is scheduled to begin in December 2026 (DOI).

Oncology and supportive care

Let’s review what remains unchanged: in this field, photobiomodulation is used as a supportive treatment for the side effects of cancer treatments, never as a treatment for cancer itself.

A meta-analysis of 13 randomized trials (1,049 participants) published inthe International Journal of Nursing Studies evaluated nonpharmacological interventions for chemotherapy-induced taste disturbances. Overall, these interventions reduce the incidence of taste disturbances (RR 0.72; 95% CI 0.61 to 0.86). In a subgroup analysis, PBM significantly improved the perception of salty (SMD 0.90; 95% CI 0.60 to 1.20), sour (SMD 0.69; 95% CI 0.09 to 1.29), and sweet (SMD 0.66; 95% CI 0.14 to 1.18) (DOI).

In radiation-induced xerostomia associated with head and neck cancers, a meta-analysis of 7 randomized trials found a reduction in oral pain (MD -0.76; 95% CI -1.33 to -0.20; moderate certainty); for both stimulated and unstimulated salivary flow, the estimates favor PBM but do not reach statistical significance, with heterogeneity exceeding 90% (DOI). A structured review of 42 publications on the same indication distinguishes between prevention, mitigation, and treatment, and cites a meta-analysis of 2,026 studies reporting an improvement in salivary flow (SMD 0.75; 95% CI 0.03 to 1.46) without an improvement in subjective xerostomia (SMD −0.07), and concludesthat no salivary biomarker or artificial intelligence model currently allows for the prediction of response (DOI).

In pediatric oncology, acceptability is just as important as efficacy. As part of a randomized crossover trial, caregivers of 32 children undergoing chemotherapy were surveyed about extraoral and intraoral PBM for the prevention of mucositis: 65.6% preferred the extraoral method; discomfort was reported in 43.8% of cases with the intraoral method compared to 6.3% with the extraoral method (p = 0.001), and intraoral care was more often perceived as providing better pain control (34.4% vs. 12.5%), although these perceptions did not correspond to differences in the incidence or severity of mucositis (DOI).

Chez le rat, dans un modèle d'ostéoradionécrose (35 Gy puis extraction dentaire, 29 animaux), une PBM infrarouge 940 nm et une PBM bi-longueur d'onde (632-650 nm + 904-940 nm) pendant 14 jours ont toutes deux augmenté l'expression d'ALP, BMP-2 et ostéonectine et réduit TRAP par rapport au groupe irradié non traité (p < 0,05), l'ALP étant plus élevée avec la bi-longueur d'onde (DOI). L'étude sur le lymphœdème après cancer du sein, négative sur ses critères principaux, est détaillée dans la section des résultats négatifs.

Neurology and Mental Health

The most significant work of the month is a translational study published in *Molecular Psychiatry* on transcranial near-infrared light (NIRL) and sleep. In mice, near-infrared stimulation significantly increases slow-wave sleep and delta power during and after stimulation, accompanied by elevated adenosine levels in the frontal cortex; in vitro, ATP production increases without cytotoxicity. In humans, a randomized, double-blind trial involving 40 subjects reported significant reductions in the severity of insomnia, sleep disturbances, and sleep onset latency, although the specific values were not detailed in the abstract (DOI).

In Alzheimer’s disease, a network meta-analysis of 36 randomized trials (1,445 patients) compared eight neuromodulation techniques. Transcranial pulse stimulation yielded the greatest improvements on the MMSE (MD 3.92; 95% CI 1.57 to 6.35) and the MoCA, while rTMS showed the greatest improvement on the ADAS-Cog (MD -11.10). PBM was among the interventions compared, but no specific results for it are provided in the abstract, and no single modality was universally superior (DOI). A study of EEG markers in 88 participants (Alzheimer’s disease, frontotemporal dementia, controls) includes an exploratory analysis of a single case undergoing PBM, showing increased alpha power and a shift in the EEG profile toward that of healthy subjects; PBM is peripheral to the main topic in this study (DOI).

The rest of the month consists mainly of reviews of mechanisms, all of which emphasize that clinical data continue to lag behind preclinical data. A review in *Clinical Science* describes the activation of cytochrome c oxidase, the regulation of neuronal oscillations and glial functions, and calls for a database of parameters organized by pathology (DOI). Others cover adult neurogenesis (DOI), the excitation-inhibition balance in neurological and psychiatric disorders (DOI), and migraine, where preclinical models show a reduction in hyperalgesia and oxidative stress but where clinical evidence remains limited (DOI). Three broader reviews place PBM among other modalities: noninvasive neuromodulation in Alzheimer’s disease with brain-heart coupling as a biomarker framework (DOI), neurostimulation in treatment-resistant depression (DOI), and a review of the engineering of electrical, magnetic, ultrasonic, and optical modalities (DOI). A bibliometric analysis of 191 publications on PBM in peripheral nervous system disorders shows a growing body of research since 2010, focused on carpal tunnel syndrome and centered on three areas: pain modulation, nerve regeneration, and mechanisms (DOI).

Two case reports are worth reading for what they are. A retrospective series of two adolescents with PANS/PANDAS that had persisted for more than ten years, treated with at-home 1070 nm transcranial PBM and neurofeedback, reports a 73% reduction in severity on the PANS-31 scale in one patient and a 50% reduction in obsessive-compulsive symptoms in the other. The authors themselves emphasize thatno conclusions regarding efficacy can be drawn (retrospective design, n = 2, concomitant interventions), and one of them is affiliated with a device manufacturer (DOI). A single-case report of a 6-year-old child with autism spectrum disorder and chronic constipation, treated for 90 days with abdominal and transcranial PBM (LED 1064 nm, 54 mW/cm², 10 min per site), describes a restructuring of the fecal microbiota as shown by 16S sequencing and a reported improvement in bowel movements and behavior, with no sham control (DOI). We addressed this topic in our article on photobiomodulation and autism.

In preclinical studies in diabetic mice, PBM alone or in combination with metformin or insulin improved neuropathy and cognitive impairments, with the combination treatments producing the most marked recovery (DOI). In a mouse model of hypoxic-ischemic brain injury, the combination of PBM and hydrogen inhalation better preserves locomotor activity and reduces neuronal loss, glial activation, and apoptosis than either treatment alone (DOI). For all these indications, PBM is not a substitute for medical follow-up or prescribed treatments. The negative meta-analysis on motor symptoms of Parkinson’s disease is discussed in the section on negative results.

Ophthalmology

Le contrôle de la myopie par lumière rouge de faible intensité répétée (RLRL) continue d'alimenter la littérature. Une étude rétrospective sur 3 ans chez 86 enfants compare la RLRL (2 séances par jour, n = 40) à l'orthokératologie (n = 46). La variation moyenne de longueur axiale était de 0,00 ± 0,28 mm avec la RLRL contre 0,45 ± 0,20 mm avec l'orthokératologie (p < 0,001) ; un raccourcissement axial d'au moins 0,05 mm était observé chez 40,0 % contre 2,17 % des enfants, et un contrôle complet (moins de 0,10 mm par an) chez 82,5 % contre 37,0 %. Un cas d'hyperréflectivité rétinienne réversible en OCT a été observé dans le groupe RLRL, sans perte visuelle (DOI).

In contrast, an exploratory, double-blind, sham-controlled, randomized trial involving 40 children aged 8 to 12 years tested low-intensity incoherent LED twice daily for 3 months. Axial elongation was lower in the treatment group, but significant only for the left eye (-0.056 mm; p = 0.036); at the participant level, the differences were no longer significant after adjustment. No serious adverse events (SAE) were reported.

Two letters round out this section. One discusses the structural retinal changes observed on OCT with repeated RLRL and their potential mechanisms (DOI), while the other comments on the cost-effectiveness analysis of PBM in intermediate dry AMD based on the 24-month LIGHTSITE III trial (DOI). The question of long-term retinal safety in children remains open, and in our view, this is the key point to monitor in this field.

Sports, Recovery, and Performance

A meta-analysis of 23 randomized trials in healthy subjects concluded that PBM has small effects on muscular endurance (p = 0.02) and strength (p = 0.04), which were more pronounced in athletes (p = 0.05) than in simply active subjects (p = 0.07). The parameters associated with endurance gains were a power output of 100 mW or less per diode, a total of 31 to 100 J, application 1 to 3 minutes before exercise, and a maximum of 4 treatment sites; strength tended to improve with 151 to 300 J and an application time of more than 3 minutes. These subgroup analyses remain exploratory (DOI).

A systematic review on muscle soreness (1,183 articles screened) reexamines the neurophysiological mechanisms according to exercise type and recommends PBM, along with compression, for recovery after resistance training, though the abstract does not provide specific quantified effects for PBM (DOI). An uncontrolled pilot study of 28 young tennis players (mean age 14.4 years) reports acute improvements in jumping performance after 15 minutes of using a wearable device; several of these improvements remained significant after Benjamini-Hochberg correction but none after Holm-Bonferroni correction (DOI).

A review in *Frontiers in Bioengineering and Biotechnology* provides an overview of skeletal muscle regeneration: modulation of cytochrome c oxidase, NO dissociation, increased ATP, and controlled ROS signaling that activates satellite cells, according to a biphasic dose-response relationship. The authors advocate for standardized dosimetry, radiometric calibration, and customized optical simulations (DOI). A randomized, placebo-controlled trial protocol in men aged 18 to 35 will compare PBM to ischemic preconditioning prior to eccentric elbow flexor exercise, with maximum isometric strength at 24, 48, and 72 hours as the primary endpoint (DOI).

Wound Healing and Dermatology

A Phase I dose-escalation trial involving 22 patients with chronic wounds established the tolerability of high-fluence 405-nm antimicrobial blue light (20, 60, or 100 J/cm², three times a week for 2 weeks). All but one patient experienced Grade 1 skin reactions (one Grade 2 phlycten), the 28 adverse events were deemed unrelated, pain was absent or mild with no difference between dose groups, and no worsening of wound healing was observed (DOI). The same team published a systematic review of 44 in vitro studies (7,508 references screened) on keratinocytes exposed to blue light: responses range from adaptive redox signaling to oxidative stress and apoptosis, with shorter wavelengths having a narrower margin between adaptive effects and cytotoxicity, and all studies present a moderate or high risk of bias (DOI).

In rats, a randomized study involving 18 animals applied PBM to the inflammatory phase of chronic wounds. On Day 3, serum ROS levels were 1.24 times higher, IL-4 was reduced by a factor of 1.58, and IL-6 was reduced by a factor of 2, with no difference observed for IL-1β, IL-10, TNF-α, bFGF, or TGF-β1; histology revealed fewer macrophages and polymorphonuclear cells and more fibroblasts (DOI). In facial plastic surgery, a narrative review on perioperative “biohacking” lists PBM among recovery strategies, alongside hyperbaric oxygen therapy and pulsed electromagnetic fields, without providing specific data (DOI).

Emerging Indications

Deux essais exploratoires sortent du cadre habituel. Chez 50 femmes euthyroïdiennes naïves de traitement atteintes de thyroïdite auto-immune chronique, un essai prospectif en ouvert et non randomisé a comparé une PBM transdermique dirigée sur la thyroïde (n = 25) à une supplémentation en sélénium et vitamine D (n = 25), avec 3 mois de suivi. L'interaction temps × groupe était significative en faveur de la PBM pour le glutathion sérique (F = 19,10 ; p < 0,0001), les anti-TPO (p = 0,001), les anti-Tg (p = 0,002) et le volume thyroïdien (p < 0,0001). Aucune patiente du groupe PBM n'a eu besoin de lévothyroxine, contre 24 % dans le groupe supplémentation. L'absence de randomisation et d'insu impose de confirmer ces résultats (DOI). Chez 7 diabétiques de type 2, une étude pilote de faisabilité a appliqué une irradiation LED multi-longueurs d'onde (660, 850 et 940 nm ; 5 mW/cm² ; 4,5 J/cm²) sur le crâne trois fois par semaine pendant 4 semaines. La glycémie à jeun (p = 0,026) et la glycémie moyenne (p = 0,044) ont diminué, avec une baisse limite de l'HbA1c (p = 0,051) ; insuline, HOMA-IR, lipides et CRP n'ont pas varié. Aucun événement indésirable, mais aucun groupe contrôle (DOI).

A randomized, double-blind, sham-controlled trial protocol will evaluate a single session of PBM (808 nm laser, 100 mW) administered within 12 hours of vaginal delivery with first- or second-degree perineal trauma, assessing pain, vulvar edema, maternal functioning, and sexual function up to 3 months (DOI). A structured review of electrotherapy in pediatric rehabilitation (2000–2026) considers the evidence for PBM and HILT to be promising but specific to certain indications, with favorable short-term tolerability and a lack of long-term safety data (DOI). Finally, the recommendations from the Fifth International Consultation on Sexual Medicine (ICSM 2024) review regenerative interventions for sexual dysfunction; the strongest evidence pertains to low-intensity shock waves for erectile dysfunction, and PBM is cited among the techniques for which studies remain methodologically limited (DOI).

In terms of devices, a Korean team describes in *ACS Applied Materials & Interfaces* a self-supporting, stretchable OLED patch designed for disposable skin phototherapy, encapsulated in Parylene-C/Al₂O₃-TiO₂ nanolaminates. The encapsulation increases the component’s operational lifespan by a factor of 19 and is resistant to immersion, bending, and biological fluids. This is a materials engineering study; no clinical efficacy data are provided (DOI).

Mechanisms and Basic Research

Three studies by the same Brazilian research team on zymosan-induced arthritis in mice (830 nm laser, 10 mW, 3 and 30 J/cm², assessments at 24, 48, and 72 h) show that PBM alters the expression of base-excision DNA repair genes, with a reduction in APE1, FEN1, and LIG1 at 24 h (DOI), as well as that of telomere maintenance genes— which were under-expressed at 24 and 48 h and then over-expressed at 72 h at high fluence (DOI)—and directs macrophages toward an anti-inflammatory M2 profile, 3 J/cm² reducing M1 cells at 24 h and 30 J/cm² promoting M2 polarization at 48 and 72 h (DOI).

In a cellular model of osteoarthritis (IL-1β-stimulated SW1353 cells), a screening of conditions at 660 nm identified 5 mW/cm² and 18 J/cm² as the most effective combination for reducing IL-6 and MMP-13 in a biphasic manner; RNA-seq revealed suppression of the TNF, NF-κB, IL-17, and JAK-STAT pathways, as well as 157 genes that were upregulated compared to the osteoarthritic profile (DOI). In an Alzheimer’s model, 808 nm PBM (30 J/cm²) restores the integrity of the mitochondrial network in hippocampal neurons exposed to amyloid-β, normalizes ROS, ATP, and membrane potential, and loses all effect when mitochondrial dynamics are blocked by Mdivi-1 (DOI). In HT22 neurons damaged by corticosterone, 808 nm PBM improves viability and restores the phosphorylation of AMPK and ULK1, effects that are largely abolished by pharmacological inhibition of AMPK (DOI).

Deux études in vitro sur des cellules souches de dents déciduales cultivées sur acide polylactique montrent qu'une irradiation unique à 660 nm module l'activité métabolique et le cycle cellulaire de façon dose-dépendante, 4 J/cm² donnant une activité supérieure au contrôle à 24, 48 et 72 h (p < 0,05) et une fraction G2/M plus élevée à 72 h (DOI), et que 1,0 J/cm² sur scaffolds électrofilés accroît la colonisation sans augmenter les cellules mortes (DOI). Sur des macrophages RAW264.7 soumis à un stress hyperglycémique et inflammatoire, la PBM 720 nm (0,3 mW/cm²) et les champs électromagnétiques pulsés atténuent chacun les marqueurs inflammatoires, et leur combinaison ramène la production de NO vers la valeur normoglycémique, sans interaction sur les cytokines (DOI). Des îlots pancréatiques murins isolés traités quotidiennement pendant 7 jours sécrètent environ deux fois plus d'insuline après 3 jours, un résultat qui intéresse la transplantation (DOI).

Deux modèles animaux élargissent le champ. Chez 24 rats soumis à une torsion-détorsion testiculaire, un laser 810 nm (100 mW, 2 J/cm², six jours) a restauré la mobilité et la viabilité des spermatozoïdes, l'architecture des tubes séminifères et l'équilibre redox testiculaire, avec hausse des enzymes antioxydantes et baisse de la peroxydation lipidique (p < 0,001) (DOI). Dans un modèle de lésion pulmonaire aiguë au LPS sur 288 rats, trois sources ont été comparées : seul le laser rouge 660 nm a réduit à la fois la mécanique ventilatoire, l'activité myéloperoxydase et les cytokines inflammatoires, la LED 430 nm n'agissant que sur certaines cytokines et le laser 808 nm réduisant TNF-α et IL-6 sans effet sur la mécanique (DOI).

Trois résultats intéressent directement la sécurité et la dosimétrie. Sur des microsphères 3D de cancer colorectal HT-29, une fluence de 80 J/cm² augmente la libération de LDH et la production de NO et réduit la densité cellulaire (p < 0,05), alors que 2 J/cm² montre un profil cytoprotecteur modeste ; la réponse des gènes Wnt est mixte et n'établit pas d'activation de la voie (DOI). Une modélisation par ray-tracing voxel de l'irradiation à 635 nm montre que l'absorption maximale se situe à 0,02-0,04 mm de profondeur et que la forte pigmentation concentre l'absorption dans l'épiderme superficiel, ce qui plaide pour adapter les doses au phototype (DOI). Enfin, chez le rat en douleur neuropathique par constriction du nerf sciatique, dix séances de PBM infrarouge augmentent les seuils de retrait et réduisent l'allodynie dans les deux sexes, avec une récupération relative plus importante chez les femelles et une sensibilité réduite en métœstrus (DOI).

Negative or neutral results

Four studies published this month do not support the expected findings, and they carry just as much weight as the others.

In chronic nonspecific neck pain, a single-blind, randomized superiority trial involving 62 patients compared an 8-week multimodal program with and without infrared laser PBM. Contrary to expectations, the significant differences favored the group without PBM in terms of disability (NDI 4.06; 95% CI 2.83 to 5.28 post-intervention; 3.23 at 1 month) and pain at rest (0.54; 95% CI 0.14 to 0.95). At the doses tested, PBM provided no additional benefit (DOI).

In Parkinson’s disease, a systematic review of 8 trials (279 patients)—which were highly heterogeneous in terms of wavelength and dosimetry—including a meta-analysis of 4 randomized trials, showed no significant effect on motor symptoms (MDS-UPDRS-III: MD -1.37 points; 95% CI -5.55 to 2.80) or on the Timed Up and Go test (MD -0.52 s), despite good tolerability. Individual effect sizes ranged from d = 0.03 to 0.41 (DOI).

In breast cancer-related lymphedema, a three-arm randomized trial involving 46 patients compared 904-nm LLLT, 650-nm LLLT, and a sham treatment as an adjunct to decongestive therapy. No between-group differences were observed in indocyanine green lymphography, bioimpedance, or tissue dielectric constant; only the variation in the superolateral shear wave velocity ratio differed (p = 0.029), a result the authors describe as exploratory (DOI). Finally, the exploratory trial on myopia using LEDs described above, in which the differences were no longer significant after adjustment (DOI).

Frequently Asked Questions

Can photobiomodulation replace an anti-inflammatory medication before surgery?

A randomized trial from September 2026 shows that a single preoperative PBM session at 810 nm is non-inferior to celecoxib in terms of pain 24 hours after total knee replacement, with less swelling and fewer gastrointestinal side effects. This is a single trial involving 80 patients, for a specific indication. It does not justify changing an analgesic protocol without consulting the surgical team.

Which dental indications for PBM are best documented?

Pain following third molar extraction, early implant stability, and burning mouth syndrome each have a meta-analysis of randomized trials as of September 2026, showing significant effects but with a certainty of evidence rated as low to very low. Temporomandibular disorders and cold sores are still awaiting higher-quality trials.

Is red light therapy safe for children with myopia?

The September data point in two directions. A 3-year study confirms that axial length control is significantly better than with orthokeratology, with one case of reversible retinal hyperreflectivity. A letter draws attention to structural retinal changes observed on OCT. The issue of long-term safety remains unresolved and requires ophthalmologic follow-up.

Does photobiomodulation work for Parkinson's disease?

Not on motor symptoms, according to a meta-analysis of four randomized trials published this month: no significant effect on the MDS-UPDRS-III, despite good tolerability. The protocols are highly heterogeneous and the sample sizes are small, which leaves the door open for trials with more carefully controlled dosing; however, as things stand, PBM has not demonstrated any motor benefit in this disease.

Does a higher dose of light produce better results?

No. In colorectal cancer cells, 80 J/cm² is cytotoxic, whereas 2 J/cm² is cytoprotective; in an osteoarthritis model, the response is biphasic, with an optimum at 18 J/cm²; in arthritis in mice, 3 and 30 J/cm² do not direct macrophages in the same way. Photobiomodulation operates within a therapeutic window, not according to a logic of increasing dose.

Key Takeaways

Three publications raise the level of evidence this month: the non-inferiority trial comparing celecoxib to knee replacement, the meta-analysis of 32 randomized trials in implantology, and the meta-analysis on taste disturbances following chemotherapy. The comparison of HILT versus ultrasound in knee osteoarthritis adds a clear clinical result, though this should be viewed in light of the conflict of interest reported in the meta-analysis on the same topic.

The rest of the month tells a more subdued story. The negative trials are well-conducted: chronic neck pain, motor symptoms of Parkinson’s disease, lymphedema following breast cancer. They do not undermine the field; they define its boundaries. A technology that fails in one area is a technology that can be taken seriously in another.

The most useful trend is that of trials comparing light to active treatments. Comparing light to a placebo answers a laboratory question; comparing it to an anti-inflammatory drug, ultrasound, or mirror therapy answers the question that practitioners are asking. As of September 2026, there are four such trials.

The areas of uncertainty remain the same: dosimetry varies from one study to another, sample sizes are often small, and several meta-analyses themselves rate the certainty of their evidence as low or very low. As long as wavelength, irradiance, energy per point, and number of sessions remain so widely varied, reviews will continue to conclude that there is insufficient evidence for indications where PBM is, in fact, effective.

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

Sources: PubMed / NCBI, publications indexed between September 1 and October 4, 2026. The DOI links lead to the original publications. The abstracts are indicative summaries; please refer to the full text before any clinical application or communication. Photobiomodulation is not a substitute for prescribed treatment; consult a healthcare professional.