THE CURE INDEX
Helio Cure's evidence score based on human clinical trials for red light therapy.
Voice disorders are conditions that affect the quality, pitch, volume, or ease of speaking when the voice system does not work normally.
The evidence for voice disorders is thin and points both ways, so red light therapy earns only a verdict of mixed evidence. The CURE Index scored the condition 36 out of 100, indicating limited confidence, drawn from just 5 human studies and 129 participants.
Where signals appeared, red light therapy was associated with small, short-term gains in voice quality and voice fatigue measures. The 5 studies were 2 randomized controlled trials, 1 clinical trial, and 2 observational studies, of which 2 reported an effective outcome and 3 reported partially effective outcomes.
The most cited wavelengths were 640 and 940 nm, within a 628 to 1100 nm range, in sessions of 30 seconds to 20 minutes, 1 to 12 times per week, over a single day of treatment.
EVIDENCE AT A GLANCE
The numbers behind the verdict.
MOST CITED WAVELENGTHS
The wavelengths appearing most often in studies that showed benefit for voice disorders.
640 nm · 940 nmTREATMENT PROTOCOL RANGES
The lowest and highest values used across voice disorders studies.
| PARAMETER | RANGE |
|---|---|
| Wavelength | 628-1100 nm |
| Session Duration | 30 seconds-20 minutes |
| Session Frequency | 1-12 per week |
Note: We have excluded meta-analyses and reviews from scoring, but the list of human studies below contains them for your reference.
6 Human Studies on Red Light Therapy for Voice Disorders
Teachers' Voice Quality Rose Right After a Single LED Session
Among 41 female schoolteachers with tired voices, a 2025 single-group trial tested one 5-minute session of LED light therapy on the voice box. The 640- and 940-nm light at 1 W was applied once, and computer-based measures of voice quality and breathing were taken just before and just after. Researchers found that voice quality and breathing improved immediately in the more affected teachers, while those with mild symptoms changed little. The authors cautioned that the study was small, lacked a comparison group, and examined only immediate effects.
- Study Type
- Clinical Trial
- Participants
- 41
- Treated Area
- Throat
- Wavelength(s)
- 640, 940 nm
- Session Duration
- 5 minutes
- Session Frequency
- 1 per week
- Therapy Duration
- 1 days
- Study Scope
- Vocal Fatigue
Study Title: A single photobiomodulation session selectively improves vocal stability and respiratory capacity in teachers with severe vocal fatigue.
Voice Experts Reached Consensus on Using Light Therapy
A 2025 study used a structured expert-consensus method to gather the views of 7 experienced voice therapists on using photobiomodulation (PBM) in voice care, rather than treating patients. The experts rated a 55-item list of statements about 660 nm light therapy, and their level of agreement was measured on an agreement scale. According to the study, the panel reached strong consensus on 34 of the items, supporting clearer rules for when and how to prescribe PBM in voice therapy.
- Study Type
- Observational Study
- Participants
- 7
- Treated Area
- Throat, Arm
- Wavelength(s)
- 660 nm
- Distance
- Contact
Study Title: Photobiomodulation on vocal training and rehabilitation: Delphi consensus based on experts.
Only the Highest Laser Dose Improved Voice Quality Measures
Three infrared laser doses, 3, 6, and 9 J per point, were tested against a placebo in a 2025 randomized trial of low-level laser therapy (LLLT) for voice quality in 36 vocally healthy women aged 18 to 45. Each dose was paired with a tongue-trill voice exercise, and computer measures of voice quality were recorded before and right after. Only the 9 J group showed a modest improvement in voice-quality measures, while the lower doses and placebo showed no change. No worsening or extra discomfort appeared, so the researchers described the approach as safe.
- Study Type
- Randomized Controlled Trial
- Participants
- 36
- Treated Area
- Throat
- Wavelength(s)
- 798-818 nm
- Distance
- Contact
- Session Duration
- 30 seconds, 60 seconds, 90 seconds
- Session Frequency
- 1 per week
- Therapy Duration
- 1 days
Study Title: Immediate effects of photobiomodulation with low-level laser in women with no laryngeal or voice changes: preliminary results.
Survey Found Voice Therapists Widely Use Light Therapy
A 2023 survey asked 29 voice therapists in Brazil how they use photobiomodulation (PBM) in their practice, rather than testing it on patients. Almost all had trained in it, and most owned a device and used it routinely, most often at 808 to 830 nm or a combined 660 and 808 nm, with 3 to 5 J per point for inflamed vocal cords and 6 to 9 J for building up the voice. The survey found that these therapists viewed PBM as a useful aid for sung and spoken performance and for vocal cord inflammation, though it measured their opinions and habits, not voice outcomes.
- Study Type
- Observational Study
- Participants
- 29
- Treated Area
- Throat
- Wavelength(s)
- 650-660, 660, 808-830, 808, 904-907 nm
- Distance
- Contact
Study Title: Opinion of speech-language pathologist on the use of photobiomodulation in the vocal clinic.
Review Called Light Therapy a Promising but Unproven Voice Aid
A 2022 review from Brazil surveyed methods for treating voice disorders, placing photobiomodulation (PBM) alongside traditional voice therapy and electrical stimulation. It noted that PBM uses red and near-infrared light from about 635 to 1100 nm applied to the voice box and vocal cords. The authors concluded that evidence for PBM in voice treatment is still limited, though it looks promising as an add-on to established therapies.
- Study Type
- Review
- Treated Area
- Throat
- Wavelength(s)
- 635-700, 808-1100 nm
- Session Frequency
- 12 per week
- Study Scope
- Vocal Disorders
Study Title: Reducing the gap between science and clinic: lessons from academia and professional practice - part B: traditional vocal therapy techniques and modern electrostimulation and photobiomodulation techniques applied to vocal rehabilitation.
Red Laser Normalized Voice-Fatigue Measures After Heavy Voice Use
Comparing red laser, infrared laser, heat, and no treatment, a 2017 randomized study tested low-level laser therapy (LLLT) for voice fatigue in 16 vocally healthy adults. After an hour of heavy voice use, each person had 628 nm red light, 828 nm infrared light, heat, or nothing applied to the front of the neck over the voice box for 20 minutes. Red LLLT at 628 nm appeared to bring the tiring measures of voice, such as the effort needed to make sound, back toward normal more than the other conditions did.
- Study Type
- Randomized Controlled Trial
- Participants
- 16
- Treated Area
- Neck
- Wavelength(s)
- 628, 828 nm
- Session Duration
- 20 minutes
- Therapy Duration
- 1 days
- Study Scope
- Dysphonia
Study Title: The Effectiveness of Low-Level Light Therapy in Attenuating Vocal Fatigue.
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