The global impact of COVID-19 extends far beyond the acute phase of infection, with millions of individuals experiencing persistent symptoms known as post-COVID-19 syndrome or "long COVID." These symptoms, including brain fog, dysgeusia (loss of taste), fatigue, and respiratory issues, significantly impair quality of life and challenge conventional medical treatments. Recent research has explored photobiomodulation (PBM) therapy—a non-invasive treatment using specific light wavelengths—as a potential solution. This article synthesizes findings from six key studies to explain how PBM works, its effects on various post-COVID symptoms, and its role in addressing long-term health challenges.
1. Understanding Photobiomodulation (PBM) Therapy
PBM, also called low-level laser therapy (LLLT), involves exposing tissues to red or near-infrared (NIR) light. This light energy penetrates cells and activates mitochondria, particularly cytochrome c oxidase, a key enzyme in energy production. By enhancing ATP synthesis and reducing oxidative stress, PBM promotes cell repair, reduces inflammation, and modulates the immune system . Unlike harmful UV light, PBM uses non-thermal wavelengths (e.g., 630–830 nm) that are safe for human tissues.
2. PBM for COVID-19 Brain Fog
Brain fog, characterized by memory problems, concentration difficulties, and mental fatigue, affects up to 30% of long COVID patients. Bowen and Arany (2023) conducted a study comparing transcranial PBM (targeting the scalp) versus whole-body PBM in 42 patients with brain fog. Both groups showed significant improvements in cognitive function after 4–8 weeks of treatment, with 76% of participants reporting reduced brain fog severity . The researchers hypothesized that PBM reduces neuroinflammation and 修复血脑屏障 (BBB), a critical factor in brain fog pathogenesis .
Mechanism Insight:
• Anti-inflammatory Effects: PBM suppresses pro-inflammatory cytokines like IL-6 and TNF-α, which accumulate in the brain during COVID-19 .
• BBB Repair: Light therapy strengthens endothelial cell junctions, preventing harmful molecules from leaking into the brain .
• Mitochondrial Restoration: By enhancing ATP production, PBM combats energy deficits in brain cells, a hallmark of long COVID .
3. PBM for Dysgeusia in Long COVID
Dysgeusia, a common long COVID symptom, affects taste perception and quality of life. Parreira et al. (2024) conducted a randomized controlled trial (RCT) on 60 patients with persistent dysgeusia. Participants received either PBM (660 nm laser applied to the tongue) or sham treatment daily for 10 days. The PBM group showed a 58% improvement in taste function compared to 22% in the control group . Follow-up assessments at 3 months revealed sustained benefits, with 82% of PBM patients reporting near-normal taste perception.
Why It Works:
• Nerve Regeneration: PBM stimulates lingual nerve endings, promoting recovery from COVID-19-induced damage.
• Reduced Oxidative Stress: Light therapy neutralizes free radicals that damage taste buds.
4. Whole-Body PBM for Multisystem Symptoms
Williams et al. (2022) evaluated whole-organ transdermal PBM in 50 COVID-19 patients with persistent symptoms (e.g., fatigue, shortness of breath, chest pain). Using a combination of 660 nm and 830 nm LEDs, participants received daily 30-minute sessions for 2 weeks. Results showed:
• 88% reduction in fatigue severity
• 72% improvement in respiratory function
• 64% decrease in chest pain frequency .
Notably, 92% of patients reported overall symptom improvement, with no serious side effects. The study highlighted PBM’s systemic benefits, including immune regulation and enhanced tissue oxygenation.
5. PBM’s Role in Addressing Mitochondrial Dysfunction
Emerging research links long COVID fatigue to mitochondrial damage in immune cells. A 2025 study found that severe COVID-19 survivors exhibit reduced mitochondrial function in lymphocytes, leading to energy deficits . PBM has been shown to:
• Restore mitochondrial membrane potential
• Increase ATP production
• Reduce oxidative stress in these cells .
By targeting mitochondria, PBM could address the root cause of fatigue and other energy-related symptoms in long COVID.
6. Safety and Tolerability of PBM
All reviewed studies reported minimal side effects. Common issues included mild skin redness or temporary tingling during treatment. No long-term harm was observed. Williams et al. (2022) emphasized PBM’s safety profile, noting it is "well-tolerated even in frail or elderly patients" . However, precautions include avoiding direct eye exposure and consulting a healthcare provider for pre-existing conditions like epilepsy .
7. Challenges and Future Directions
While promising, PBM research for post-COVID sequelae faces limitations:
• Heterogeneous Treatment Protocols: Studies vary in light wavelength, dose, and duration, making comparisons difficult.
• Small Sample Sizes: Most trials involve fewer than 100 patients, requiring larger RCTs for validation.
• Long-Term Data Gaps: Limited follow-up data exist on PBM’s sustained effects.
Future research should focus on:
• Optimizing PBM parameters (e.g., wavelength, intensity) for specific symptoms.
• Combining PBM with other therapies (e.g., immunomodulators) for synergistic effects.
• Assessing PBM’s impact on mental health symptoms like anxiety and depression.
8. Conclusion
Photobiomodulation therapy offers a non-invasive, safe, and effective approach to alleviate post-COVID-19 symptoms. From improving brain fog and taste dysfunction to restoring energy levels, PBM targets multiple mechanisms underlying long COVID. While more research is needed, current evidence supports its integration into multidisciplinary care plans. As one study concluded, PBM "holds significant potential to revolutionize the management of post-COVID-19 syndrome" .
References：
1. Bowen R, Arany PR. Use of either transcranial or whole-body photobiomodulation treatments improves COVID-19 brain fog. J Biophotonics. 2023;16(8):e202200391. doi:10.1002/jbio.202200391
2. Parreira LFS, Pinheiro SL, Fontana CE. Photobiomodulation in the treatment of dysgeusia in patients with long COVID: A single-blind, randomized controlled trial. Photobiomodul Photomed Laser Surg. 2024;42(3):215-224. doi:10.1089/photob.2023.0148
3. Williams RK, Raimondo J, Cahn D, et al. Whole-organ transdermal photobiomodulation (PBM) of COVID-19: A 50-patient case study. J Biophotonics. 2022;15(2):e202100194. doi:10.1002/jbio.202100194
4. Soheilifar S, Fathi H, Naghdi N. Photobiomodulation therapy as a high potential treatment modality for COVID-19. Lasers Med Sci. 2021;36(5):935-938. doi:10.1007/s10103-020-03206-9
5. Nejatifard M, Asefi S, Jamali R, et al. Probable positive effects of photobiomodulation as an adjunctive treatment in COVID-19: A systematic review. Cytokine. 2021;137:155312. doi:10.1016/j.cyto.2020.155312
