THE CURE INDEX
Helio Cure's evidence score based on human clinical trials for red light therapy.
Taste disorders are conditions in which a person's sense of taste is reduced, altered, or lost.
Most of the taste research followed two triggers: taste loss after COVID-19 and taste blunting during cancer chemotherapy. Across 8 human studies and 494 participants, red light therapy was associated with faster recovery of taste in both settings, enough for a verdict of effective. The CURE Index placed the condition at 84 out of 100, indicating strong confidence.
Of the 8 studies, 6 were randomized controlled trials, and 2 were clinical trials. 7 reported effective outcomes, and 1 found no significant benefit.
Treatment favored 660 nm, within a 620 to 1400 nm range, in sessions of 30 seconds to 10 minutes given 1 to 10 times per week, over 1 to 63 days.
EVIDENCE AT A GLANCE
The numbers behind the verdict.
MOST CITED WAVELENGTH
The wavelength appearing most often in studies that showed benefit for taste disorders.
660 nmTREATMENT PROTOCOL RANGES
The lowest and highest values used across taste disorders studies.
| PARAMETER | RANGE |
|---|---|
| Wavelength | 620-1400 nm |
| Session Duration | 30 seconds-10 minutes |
| Session Frequency | 1-10 per week |
| Therapy Duration | 1-63 days |
Note: We have excluded meta-analyses and reviews from scoring, but the list of human studies below contains them for your reference.
9 Human Studies on Red Light Therapy for Taste Disorders
Single Case Reported Taste Recovery With Red and Infrared Light
2026 brought a single-patient case report of red and near-infrared light therapy for loss of taste in Brazil. The patient received 660 and 808 nm light at 25 J/cm², given about 3 to 4 times a week. According to the report, the treatment was linked to improved taste in this one case, though a single case cannot show how well it works in general.
- Study Type
- Clinical Trial
- Participants
- 1
- Treated Area
- Mouth
- Wavelength(s)
- 660, 808 nm
- Session Frequency
- 3.5 per week
Study Title: Talquetamab-Induced Dysgeusia Successfully Treated With Photobiomodulation Therapy.
Tongue Light Therapy Lowered Taste Changes During Stem-Cell Transplant
A 2024 randomized trial evaluated photobiomodulation (PBM) for taste changes in people undergoing a stem-cell transplant in Brazil. Among 85 participants, 42 in the transplant group had 660 nm light applied to the top of the tongue at 100 mW and 8.8 J/cm². The protocol reduced taste changes and helped prevent wasting of the small bumps on the tongue, the researchers reported.
- Study Type
- Randomized Controlled Trial
- Participants
- 85
- Treated Area
- Tongue
- Wavelength(s)
- 660 nm
- Study Scope
- Dysgeusia
Study Title: Photobiomodulation minimizes taste changes during hematopoietic cell transplantation: A randomized clinical trial.
Whole-Body Light Therapy Outperformed Sham for Long-COVID Taste Loss
Comparing active photobiomodulation (PBM) against a sham, a 2024 randomized controlled trial in Brazil treated 70 people with altered taste after long COVID. 34 received 660 nm red light at 18 spots on the sides of the tongue, over the glands that make saliva, and along the main artery in the neck, while 36 received a sham, and all also had weekly smell training for 8 weeks. Researchers found that taste improved in both groups, but significantly more with PBM by the seventh and eighth weeks.
- Study Type
- Randomized Controlled Trial
- Participants
- 70
- Treated Area
- Head And Neck
- Wavelength(s)
- 660 nm
- Session Duration
- 30 seconds, 10 minutes
- Session Frequency
- 8 per week
- Therapy Duration
- 56 days
Study Title: Photobiomodulation in the Treatment of Dysgeusia in Patients with Long COVID: A Single-Blind, Randomized Controlled Trial.
No Clear Winner Among Light Therapies for COVID Taste Loss
No clear difference emerged between treatments in a 2023 double-blind randomized trial of long-term taste loss after COVID-19. Patients whose taste had not returned for at least 2 months were split across 6 groups, including photobiomodulation (PBM) to the tongue at 660 or 808 nm, laser aimed at the blood through the underside of the tongue, vitamin B supplements, and a sham laser, each over 8 sessions. Light-based treatments appeared to do somewhat better than the others, but none brought a full return of taste.
- Study Type
- Randomized Controlled Trial
- Treated Area
- Tongue
- Wavelength(s)
- 660, 808 nm
- Therapy Duration
- 28, 56 days
Study Title: Photobiomodulation, Transmucosal Laser Irradiation of Blood, or B complex as alternatives to treat Covid-19 Related Long-Term Taste Impairment: double-blind randomized clinical trial.
94% of Laser Patients Regained Full Taste After COVID
17 of 18 patients regained their full sense of taste after low-level laser therapy (LLLT), compared with partial recovery in 7 of 18 given a placebo, in a 2023 randomized controlled trial in Egypt. The 36 patients had lost their sense of taste after COVID-19 and received an 810 and 940 nm diode laser, or a placebo light, at 4 J/cm² over 6-minute sessions. Complete taste recovery reached 94% in the laser group versus 39% in the placebo group, suggesting the treatment appeared to speed recovery.
- Study Type
- Randomized Controlled Trial
- Participants
- 36
- Treated Area
- Mouth
- Wavelength(s)
- 810, 940 nm
- Session Duration
- 6 minutes
- Session Frequency
- 1 per week
- Therapy Duration
- 1 days
- Study Scope
- Ageusia, Loss Of Taste
Study Title: Diode laser in management of loss of taste sensation in patients with post-COVID syndrome: a randomized clinical trial.
Breast Cancer Patients Retained Higher Taste Sense With Light Therapy
Among 112 breast cancer patients receiving chemotherapy, a 2022 triple-blind randomized trial in Brazil tested photobiomodulation therapy (PBMT) to protect the sense of taste. The treatment group had red light at 650 to 670 nm and infrared light at 798 to 818 nm applied to 21 points on the tongue on the first day of each of 4 chemotherapy cycles, while the others received a sham. Patients given PBMT kept significantly more of their sense of taste, reported better quality of life, and had less weight loss and fewer mouth sores than the sham group.
- Study Type
- Randomized Controlled Trial
- Participants
- 112
- Treated Area
- Tongue
- Wavelength(s)
- 650-670, 798-818 nm
- Distance
- Contact
- Session Frequency
- 4 per week
- Therapy Duration
- 63 days
Study Title: Photobiomodulation therapy prevents dysgeusia chemotherapy induced in breast cancer women treated with doxorubicin plus cyclophosphamide: a triple-blinded, randomized, placebo-controlled clinical trial.
COVID-Related Loss of Taste Recovered With Light Therapy on Tongue
10 patients who lost some or all of their sense of taste after COVID-19 took part in a 2022 clinical trial of photobiomodulation therapy (PBMT) in Brazil. The 8 women and 2 men, averaging around 40 and 31 years of age, received 660 nm light at 100 mW and 2 J per point across the top and sides of the tongue, in one of 3 session schedules. The trial found that taste improved in all 10 patients, whatever the schedule used.
- Study Type
- Clinical Trial
- Participants
- 10
- Treated Area
- Mouth
- Wavelength(s)
- 660 nm
- Distance
- Contact
- Session Frequency
- 5, 10 per week
- Therapy Duration
- 14, 35, 70 days
Study Title: A Brazilian multicenter pilot case series on the efficacy of photobiomodulation therapy for COVID-19-related taste dysfunction.
Review Found Light Therapy Partly Helped COVID Taste Loss
Across 1275 people in 25 studies, a 2023 review from Japan weighed treatments for taste loss and dry mouth after COVID-19, including light therapy. It described photobiomodulation (PBM) protocols using red and near-infrared light from 660 to 810 nm applied to the tongue, cheek, and the glands that make saliva. The authors concluded that light therapy showed partial promise for these COVID-related taste and saliva problems, though the underlying mechanisms remained unclear.
- Study Type
- Review
- Participants
- 1275
- Treated Area
- Mouth
- Wavelength(s)
- 660, 680, 808, 810 nm
- Session Duration
- 10 seconds, 72 seconds, 2 minutes, 2.4 minutes
- Session Frequency
- 6, 10, 12, 24 per week
Study Title: Treatments of COVID-19-Associated Taste and Saliva Secretory Disorders.
Two Wavelengths Together Protected Taste Better Than Either Alone
Red-only, infrared-only, and combined red-plus-infrared laser therapy were compared in a 2025 triple-blind randomized trial of chemotherapy-related taste loss in 180 breast cancer patients in Brazil. Each group of 60 received 2 J of red or 3 J of infrared light, or both, at 23 points on the tongue during chemotherapy. The trial found that red or infrared light on its own was less effective than the combined red-plus-infrared protocol, which better protected taste and saliva. Using a single wavelength alone did not prevent taste loss as well as the two together.
- Study Type
- Randomized Controlled Trial
- Participants
- 180
- Treated Area
- Mouth
- Wavelength(s)
- 620-780, 780-1400 nm
Study Title: Influence of different photobiomodulation protocols on the prevention of chemotherapy-induced dysgeusia in breast cancer patients treated with Doxorubicin-Cyclophosphamide: a phase III, randomized, triple-blinded non-inferiority clinical trial.
The CURE Index (Clinical Understanding of Red-light Evidence) by Helio Cure is a 0-100 evidence score based on published human clinical trials. Higher scores mean stronger evidence. Read full methodology →
Data is powered by AI and reviewed by the Helio Cure team.
This page is for educational purposes only. Not medical advice. Consult a healthcare provider before starting red light therapy. Helio Cure does not diagnose, treat, or cure any medical condition.
Last updated: Jul 28, 2026