Red Light Therapy (Photobiomodulation) for Multiple Sclerosis: Wavelengths, Mechanisms, and Clinical Outcomes

Introduction

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system, marked by inflammatory demyelination and neurodegeneration. Current disease-modifying therapies (e.g. interferon-β, ocrelizumab) primarily target immune activity to reduce relapses, but many patients still experience progressive disability and symptoms like fatigue, mobility impairment, pain, and cognitive decline. Photobiomodulation (PBM) – also known as low-level laser or red light therapy – has emerged as a non-invasive treatment that uses red to near-infrared light to modulate cellular function and promote healingpmc.ncbi.nlm.nih.gov. PBM has gained attention for its neuroprotective potential in neurological disorders, and recent medical literature suggests it may benefit MS patients when used alongside standard therapiespmc.ncbi.nlm.nih.gov. This report reviews the evidence from human clinical studies (and supporting preclinical findings) on PBM in MS, focusing on effective wavelengths (590–1080 nm range), mechanisms of action, and observed benefits on MS symptoms and disease markers.

Mechanisms of Action in MS

Mitochondrial Modulation: A central mechanism of PBM is the absorption of photons by mitochondrial cytochrome c oxidase, which enhances electron transport and ATP productionpmc.ncbi.nlm.nih.gov. In toxin-inactivated neurons, red/NIR light can restore mitochondrial function and increase cellular energy availabilitypmc.ncbi.nlm.nih.gov. This boost in mitochondrial output is critical in MS, where chronic oxidative/nitrosative stress and energy failure contribute to neurodegeneration. Indeed, PBM has been shown to reduce markers of oxidative stress (e.g. nitric oxide and nitrite levels) in MS modelspmc.ncbi.nlm.nih.gov. By improving mitochondrial redox signaling and ATP synthesis, PBM may counteract MS-related fatigue and support the energy demands of demyelinated neurons.

Anti-Inflammatory and Immune Effects: MS pathology is driven by pro-inflammatory immune responses against myelin. PBM has demonstrated significant immunomodulatory effects. Clinical studies show that repeated PBM sessions can increase anti-inflammatory cytokines like interleukin-10 (IL-10) in MS patientspmc.ncbi.nlm.nih.gov. In a 14-patient trial (808 nm, 24 sessions), PBM led to a 3-4 fold rise in IL-10 levels in peripheral blood, indicating an enhanced anti-inflammatory profilejournals.plos.org. At the same time, PBM tends to decrease pro-inflammatory mediators: ex vivo experiments with MS patient immune cells showed 830 nm light reduced interferon-γ (IFN-γ) production while increasing IL-10pubmed.ncbi.nlm.nih.gov. Animal MS models similarly confirm that PBM suppresses Th1/Th17 cytokines (e.g. IFN-γ, TNF-α, IL-17) and reduces inflammatory cell infiltration in the CNSpmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. Notably, PBM’s upregulation of IL-10 is therapeutically meaningful, as MS patients normally have deficient IL-10 levels regulating their immune cellspmc.ncbi.nlm.nih.gov. By shifting the immune milieu toward an anti-inflammatory state, PBM can help dampen the neuroinflammatory cascade thought to drive lesion formation and tissue damage in MS.

Neuroprotection and Remyelination: Beyond immunomodulation, photobiomodulation may directly support neural tissue integrity. Studies in MS models have found PBM raises expression of anti-apoptotic proteins (e.g. Bcl-2) and lowers pro-apoptotic signals, thereby protecting neurons and oligodendrocytes from programmed cell deathpmc.ncbi.nlm.nih.gov. In demyelinated rodent brains, PBM also attenuated astrogliosis and microglial activation, indicating a calmer glial environment more conducive to repairpmc.ncbi.nlm.nih.gov. Intriguingly, PBM has been reported to increase oligodendrocyte precursor cells and spur remyelination in some preclinical modelspmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. There is also evidence that PBM triggers release of neural growth factors and neurotrophic signals, which could foster synaptic plasticity and axonal survivalpmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. These neuroprotective actions suggest PBM might slow MS progression by safeguarding neurons and encouraging myelin repair. Although these mechanisms are still being elucidated, the cumulative effect – reduced oxidative stress, tempered inflammation, and enhanced cell survival – aligns with a multifaceted therapeutic benefit in MSpmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov.

Wavelengths and Treatment Parameters in Studies

Photobiomodulation encompasses light in the red to near-infrared spectrum (~600–1100 nm). Within this range, specific wavelengths have been explored in MS trials for their tissue penetration and cellular effects:

• Visible Red Light (630–670 nm): Red wavelengths have shorter penetration depths (on the order of millimeters to 1–2 cm in tissue), suitable for superficial targets or circulating immune cells. A Polish trial by Kubsik et al. used a 650 nm low-level laser on MS patients, reporting significant functional improvements (discussed below)pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. LED arrays at 670 nm have shown efficacy in EAE (an MS animal model) by reducing disease severitypmc.ncbi.nlm.nih.gov, suggesting this band can modulate inflammation even if direct CNS penetration is limited. Red-light (640 nm) was also part of a multi-wavelength regimen in a recent MS studypmc.ncbi.nlm.nih.gov. While red light mainly affects peripheral or blood-mediated pathways due to limited depth, it can still trigger systemic anti-inflammatory effects via circulating cells.

• Near-Infrared Light (808–850 nm): NIR wavelengths around 800 nm are widely used in PBM for neurological targets because they penetrate deeper into tissue (several centimeters)kamj.journals.ekb.eg. An Iranian trial applied 808 nm laser PBM in MS patients, finding a pronounced increase in IL-10 cytokine levels after 24 sessionspmc.ncbi.nlm.nih.gov. Similarly, an Egyptian RCT on MS spasticity used an 850 nm low-intensity laser, which significantly reduced spinal H-reflex latency (indicating decreased spasticity) when added to standard therapykamj.journals.ekb.egkamj.journals.ekb.eg. Wavelengths in the ~800–850 nm range have a strong track record in PBM research for activating mitochondrial pathways in neurons and are thought to reach CNS structures when applied transcranially or along the spine. The evidence to date suggests 808–850 nm light can effectively engage anti-inflammatory and neuroprotective mechanisms in MS patients.

• Deeper Penetrating NIR (904–1064 nm): Some studies have employed longer NIR wavelengths, often in pulsed laser devices. For instance, 904–905 nm light (often pulsed) was combined with red/blue light in a 2024 trial on MS exercise performancepmc.ncbi.nlm.nih.gov. That study delivered 640 nm, 875 nm, and 905 nm light together, illustrating a multi-wavelength strategy to stimulate muscle and nerve tissues at different depths; it reported improved muscle strength (details below). Wavelengths around 905 nm are known for good tissue penetration and are commonly used in laser therapy for deep tissues. Additionally, transcranial PBM at 1064 nm (just beyond 1000 nm) has shown cognitive benefits in other conditions (e.g. improving memory and EEG activity in older adults)pmc.ncbi.nlm.nih.gov, and has been proposed for MS to reach deeper brain regions. While no published MS trial has yet isolated 1060+ nm light, its successful use in neuropsychiatric PBMpmc.ncbi.nlm.nih.gov suggests it could be explored for MS cognitive impairment or chronic lesions.

Treatment Parameters: PBM doses in MS studies have varied, but a common approach is multiple sessions over weeks, targeting either systemic points or specific lesion areas. Power outputs are typically in the low to mid-range (e.g. 50–150 mW lasers or high-intensity LEDs), with exposure times from a few seconds up to minutes per point. For example, Kubsik et al. used 50 mW at 650 nm on 20 points per sessionpmc.ncbi.nlm.nih.gov, whereas Silva et al. used 100 mW at 808 nm for 6 minutes per session (giving ~36 J per session) delivered to the sublingual tissue or radial arteryjournals.plos.orgjournals.plos.org. Some protocols apply PBM transcranially or over the spinal column, while others aim at blood-rich areas (sublingual, radial artery) to induce systemic immune modulationjournals.plos.org. The optimal PBM regimen for MS is not yet established – ongoing research is refining parameters like wavelength, dose, pulse mode, and treatment duration. Notably, across studies no serious adverse effects have been reported, underscoring PBM’s safety profile even at higher wavelengths and energiespmc.ncbi.nlm.nih.gov. Patients generally tolerate the light therapy well, which supports its feasibility as a long-term adjunct treatment.

Clinical Evidence: Trials and Outcomes in MS

Though large-scale trials are still lacking, a number of small clinical studies (including randomized controlled trials and pilot studies) have examined PBM in people with MS. These provide proof-of-concept for benefits in various domains:

• Motor Function and Mobility: Improvements in mobility and disability scores have been noted with PBM. Kubsik et al. (2016) treated 20 MS patients with a 650 nm laser (along with magnetostimulation) over 21 sessions. They observed significant improvement in patients’ functional status, as quantified by a one-point reduction in the Expanded Disability Status Scale (EDSS) and better scores on the Barthel Index of daily activitiespmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. This suggests PBM helped restore some neurological function or endurance. In Egypt, Essa et al. (2016) conducted an RCT where one group received 850 nm laser therapy in addition to standard methylprednisolone. After 12 sessions, that PBM group showed shortened H-reflex latencies (reflecting reduced lower-limb spasticity) and maintained gains at 3-month follow-upkamj.journals.ekb.egkamj.journals.ekb.eg. Another group in the same study received ultraviolet B light (280–320 nm) and had a modest EDSS improvementkamj.journals.ekb.eg, but interestingly the laser (PBM) was superior for immediate spasticity reliefkamj.journals.ekb.eg. Collectively, these trials indicate that PBM can improve motor outcomes – likely by easing spasticity and enhancing neuromuscular function – which translates to better mobility and ADLs for MS patients.

• Muscle Strength and Fatigue: Muscle weakness and exercise-induced fatigue are common MS symptoms that limit activity. Photobiomodulation may counteract these by boosting muscular energy metabolism. A 2024 randomized trial by Rouhani et al. targeted limb muscles in people with relapsing-remitting MS using a combination of red and infrared light (640 nm, 875 nm, 905 nm, pulsed). After just 4 PBM sessions, the treatment group showed improved muscle force recovery and increased strength compared to baselinepmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. The investigators noted better performance on muscle contraction tests, suggesting PBM enhanced muscle endurance or reduced inflammatory muscle fatigue. In the study’s extended phase (after additional sessions over weeks), trends toward improved exercise tolerance were observed (as reported in abstract) – aligning with PBM’s known effects in healthy athletes. Mechanistically, irradiating muscle tissue can ramp up mitochondrial ATP production and cut down local oxidative stress, thereby delaying fatigue onsetpbmfoundation.orgpbmfoundation.org. Although clinical data are still preliminary, these results support PBM as a potential therapy for MS-related muscle fatigue, helping patients sustain activity with less exhaustion.

• Pain and Sensory Symptoms: MS often involves neuropathic pain (e.g. trigeminal neuralgia, limb dysesthesia) and other sensory issues. PBM may offer relief by reducing neuroinflammation and promoting nerve repair. In a 2013 study, Seada et al. applied transcranial low-level laser therapy (830 nm) to MS patients suffering from trigeminal neuralgia, a severe facial pain linked to demyelination. After 24 laser sessions (3× weekly), patients had markedly reduced trigeminal pain and improved jaw function (increased mouth opening, stronger masseter/temporalis muscle function)pmc.ncbi.nlm.nih.gov. This was a head-to-head comparison against transcranial electromagnetic stimulation, and the laser therapy showed comparable or superior pain reductionpmc.ncbi.nlm.nih.gov. The analgesic effect of PBM likely stems from its anti-inflammatory action on cranial nerve roots and perhaps direct modulation of pain-signaling pathways. Separately, PBM’s impact on spasticity (as noted above) also contributes to pain relief, since muscle spasticity can cause discomfort and cramps. Patients in PBM groups often report less spasmodic pain and rigidity. While more research is needed on neuropathic pain syndromes, these findings hint that PBM can alleviate certain MS-related pain conditions and improve sensory nerve function.

• Cognitive and Other Neurological Outcomes: Cognitive impairment (memory loss, slowed processing) can affect people with MS, and there is interest in PBM’s neuromodulatory effects on the brain. No large trials have specifically examined cognition in MS with PBM, but some studies incidentally noted improvements in mental or sensory function. The systematic review by Oliveira et al. (2024) found that across the reported cases, PBM was associated with improved cognitive and sensorial function in MS patientspmc.ncbi.nlm.nih.gov. For example, patients often describe clearer thinking and better mood after weeks of light therapy (though subjective, this aligns with PBM trials in depression and Alzheimer’s disease). PBM can increase cerebral blood flow and brain metabolism via nitric oxide release and mitochondrial activation, which could underlie cognitive benefits. Additionally, by reducing fatigue and improving sleep (as suggested in other PBM research), it may secondarily sharpen cognitive function in MS. While concrete evidence in MS is limited, ongoing studies are examining transcranial NIR light for cognitive rehab. Given that 1060–1070 nm PBM has enhanced memory and EEG rhythms in non-MS older adultspmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov, a similar approach might be fruitful in addressing MS-related cognitive decline. Future trials will clarify this potential, but current theoretical and anecdotal data support PBM’s role in overall neurological improvement beyond just motor symptoms.

Summary of Notable PBM Studies in MS (Wavelengths and Outcomes)

To highlight the range of approaches, the table below summarizes key human studies of PBM in MS and their findings:

• Kubsik et al., 2016: 650 nm laser (50 mW, 21 sessions) on 20 points per session. Outcome: Improved disability scores (EDSS improved by ~1.0; better daily living function)pmc.ncbi.nlm.nih.gov. No adverse effects noted.

• Seada et al., 2013: 830 nm transcranial laser (15 mW, 24 sessions). Outcome: Reduced trigeminal neuralgia pain and increased jaw range-of-motion in MS patientspmc.ncbi.nlm.nih.gov. Showed PBM can alleviate focal neuropathic pain.

• Silva et al., 2020: 808 nm intraoral PBM (100 mW, 6 min, 24 sessions) applied to sublingual or radial artery (14 RRMS patients, no sham control). Outcome: IL-10 levels tripled on average (from ~2.8 to 8–12 pg/mL) indicating an anti-inflammatory shift; nitrite levels were unchangedjournals.plos.orgjournals.plos.org. Proposed PBM as immune-modulating adjunct therapyjournals.plos.org.

• Rouhani et al., 2024: Multi-wavelength PBM (640 nm + 875 nm + 905 nm, pulsed, 4 sessions) targeting leg muscles (randomized trial). Outcome: Muscle strength and recovery improved, with treated MS patients showing greater post-exercise force vs. baselinepmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. Suggests benefit for MS-related weakness/fatigue.

• Essa et al., 2016: 850 nm low-level laser (12 sessions) added to IV steroid in RRMS (RCT with 24 patients). Outcome: Reduced spasticity acutely – PBM group had significant decrease in H-reflex latency, correlating with muscle relaxant effectkamj.journals.ekb.eg. EDSS disability scores improved more with UVB in this study, but PBM excelled in spasticity reliefkamj.journals.ekb.eg. Demonstrated PBM’s short-term neuromuscular benefits.

(Note: In all studies above, PBM was well-tolerated with no serious side effects reported. Session counts ranged from 4 to 24, generally over 2–8 weeks.)

PBM as an Adjunct to Standard MS Therapies

An important consideration is how photobiomodulation might integrate with existing MS treatments. All clinical studies to date have used PBM alongside standard care – patients continued their disease-modifying drugs (e.g. interferons, glatiramer, natalizumab) or received concurrent corticosteroids during relapseskamj.journals.ekb.egkamj.journals.ekb.eg. No interactions or safety issues have been reported; PBM’s mechanism is distinct from pharmacological immune suppression, so it does not interfere with drug action. Instead, PBM addresses complementary pathways – for example, nitrosative stress and mitochondrial dysfunction are largely unaddressed by MS drugs, but PBM can reduce nitric oxide-related radicals and improve mitochondria as shown in lab studiespubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov. This suggests PBM could fill a therapeutic gap by protecting tissues and mitigating damage even as immunotherapies work to prevent new lesions. Researchers have noted that “PBM can be a promising non-pharmacological intervention for MS” to augment standard treatments, given its modulation of inflammation, oxidative stress and apoptosis markerspmc.ncbi.nlm.nih.gov. The absence of adverse events in PBM trials is also encouragingpmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov, pointing to its feasibility for long-term use (unlike some drugs that have cumulative toxicities).

It’s worth noting that in one combined-modality trial (Essa 2016), UVB phototherapy plus standard steroid improved EDSS, while adding 850 nm laser PBM to UVB did not confer additional EDSS benefitkamj.journals.ekb.eg. The authors speculated there might be an unexpected interaction or simply diminishing returns when two light therapies were used togetherkamj.journals.ekb.eg. However, this was a small study and doesn’t detract from the individual efficacy of PBM. Overall, current evidence supports using PBM as an adjunct – not replacing first-line drugs, but rather complementing them by promoting tissue repair and symptom relief. Ongoing clinical trials (e.g. NCT03360487 in Brazil) are explicitly evaluating PBM plus standard medications vs. meds alone, which will clarify any synergistic effectscenterwatch.com. If PBM consistently shows additive benefits (improved quality of life, less fatigue, slower progression) on top of conventional therapies, it could become part of comprehensive MS management in the future.

Conclusion

Emerging clinical research indicates that photobiomodulation – using red to near-infrared light in the 600–1000+ nm range – offers a promising supportive therapy for multiple sclerosis. Human trials, though mostly small, have demonstrated that PBM can modulate key pathological mechanisms of MS: reducing inflammatory cytokines (while boosting anti-inflammatory IL-10)pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov, diminishing oxidative and nitrosative stresspmc.ncbi.nlm.nih.gov, and protecting neurons and oligodendrocytes from apoptosispmc.ncbi.nlm.nih.gov. These effects translate into tangible clinical improvements – patients treated with PBM have shown better motor function (lower disability scores, enhanced muscle strength)pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov, relief of certain symptoms like neuropathic pain and spasticitypmc.ncbi.nlm.nih.govkamj.journals.ekb.eg, and indications of cognitive/sensory benefitspmc.ncbi.nlm.nih.gov. Importantly, no adverse effects have been reported in the published studies, highlighting PBM’s safety and tolerability even with repeated sessionspmc.ncbi.nlm.nih.gov.

Specific light wavelengths used in MS studies span from the orange-red end (around 632–670 nm) to the near-IR (808, 830, 850, 904 nm), and even multi-wavelength combinations have been successfulpmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. While no single “best” wavelength has been identified, deeper-penetrating NIR light (≈800–900 nm) appears particularly effective for targeting CNS inflammation and is commonly employedkamj.journals.ekb.egpmc.ncbi.nlm.nih.gov. The depth of effect increases with wavelength, enabling transcranial or trans-spinal PBM to influence the brain and spinal cord in MS. At the same time, peripheral treatment (e.g. via blood or lymphatic routes) with red/NIR light can induce systemic immune modulation, which is a clever strategy in MS as shown by increased IL-10 after sublingual PBMjournals.plos.orgjournals.plos.org.

In summary, red light therapy/photobiomodulation is carving out a role as a multifaceted therapy that supports neurological function, reduces inflammation, and potentially aids tissue repair in MS. It is not a stand-alone cure – but when combined with conventional MS medications, PBM may improve patient outcomes by addressing aspects of the disease that drugs do not fully control (mitochondrial dysfunction, residual symptoms, etc.). As of 2025, the field is still in early stages: larger randomized trials are needed to confirm efficacy, optimize treatment parameters, and determine which MS subtypes or stages respond best. Researchers are also working to standardize PBM protocols for consistencypmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov. Despite these open questions, the evidence to date is encouraging. PBM has shown measurable benefits like better EDSS scores, higher anti-inflammatory cytokines, and stronger muscles in MS patients – all achieved with a low-risk, non-invasive intervention. For individuals grappling with fatigue, spasticity or slow recovery in MS, photobiomodulation could soon become an attractive adjunct therapy to “shine light” on improving their quality of life.

Sources: Recent medical journal publications and clinical trial data on photobiomodulation in MS have been used to prepare this review. Key references include: Oliveira et al., 2024 (Frontiers in Neurology)pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov; Vafaei-Nezhad et al., 2022 (J. Lasers Med. Sci)pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov; Silva et al., 2020 (PLOS ONE)journals.plos.orgjournals.plos.org; Kubsik et al., 2016 (NeuroRehabilitation)pmc.ncbi.nlm.nih.gov; Rouhani et al., 2024 (Mult Scler Relat Disord)pmc.ncbi.nlm.nih.gov; Seada et al., 2013 (J. Phys. Ther. Sci)pmc.ncbi.nlm.nih.gov; Essa et al., 2016 (Kasr Al Ainy Med J)kamj.journals.ekb.egkamj.journals.ekb.eg; and Tolentino et al., 2022 (Photobiomodul. Photomed. Laser Surg.)pubmed.ncbi.nlm.nih.gov, among others. These studies collectively underpin the conclusions drawn about red light therapy’s mechanisms and benefits in multiple sclerosis.