THE CURE INDEX
Helio Cure's evidence score based on human clinical trials for red light therapy.
Hair loss, also called alopecia, is the loss of scalp hair that leads to thinning or bald patches.
Red light therapy was found effective for hair loss across 4 human studies covering 125 participants. This condition earned a CURE Index score of 64 out of 100, indicating moderate confidence.
Studies reported that red light therapy led to increased hair density in hair loss, though the size of the benefit varied by trial.
Of the 4 studies, 3 were clinical trials, and 1 was an observational study. Effective outcomes were reported in 2 studies, partially effective outcomes in 1, and no significant benefit in 1.
Among the wavelengths tested, 650 nm was most often reported as effective, within a wider range of 630 to 14000 nm. Protocols varied from 30 seconds to 20 minutes per session, 2 to 15 sessions per week, and 90 to 270 days of therapy.
EVIDENCE AT A GLANCE
The numbers behind the verdict.
MOST CITED WAVELENGTH
The wavelength appearing most often in studies that showed benefit for hair loss.
650 nmTREATMENT PROTOCOL RANGES
The lowest and highest values used across hair loss studies.
| PARAMETER | RANGE |
|---|---|
| Wavelength | 630-14000 nm |
| Session Duration | 30 seconds-20 minutes |
| Session Frequency | 2-15 per week |
| Therapy Duration | 90-270 days |
Note: We have excluded meta-analyses and reviews from scoring, but the list of human studies below contains them for your reference.
5 Human Studies on Red Light Therapy for Hair Loss
Red and Infrared Light Outpaced Far-Infrared for Hair Loss
3 separate wavelengths of photobiomodulation, red light at 650 nm, infrared light at 1550 nm, and far-infrared light at 14000 nm, were tested against a control group in a 2025 clinical trial for hair loss. 68 participants aged 18 to 60 were assigned to 1 of the 3 light arms or a control group, receiving sessions of 30 to 60 seconds, 10 to 15 times per week, at irradiances of 1000 to 2500 mW/cm² and doses of 3 to 5 J/cm², with maintenance treatment every 4 to 6 weeks for up to 9 months. Hair density, the number of hairs in a set patch of scalp, appeared to rise in all 3 treated groups after 9 months, from about 100 to 114 hairs/cm² in the 650 nm group, 99 to 115 hairs/cm² in the 1550 nm group, and 101 to 107 hairs/cm² in the 14000 nm group, while the control group's density fell from about 100 to 98 hairs/cm². Among the 42 participants who started with an oily scalp, that condition improved in every treatment group, with oily-scalp cases nearly cut in half.
- Study Type
- Clinical Trial
- Participants
- 68
- Treated Area
- Head
- Wavelength(s)
- 650, 1550, 14000 nm
- Session Duration
- 30 seconds, 45 seconds, 60 seconds
- Session Frequency
- 10, 12, 15 per week
- Therapy Duration
- 90-270 days
Study Title: Clinical Trial Comparing Three Wavelengths in Photobiomodulation Therapy for Hair Loss.
Hair Density Improved After Helmet-Style Light Therapy for Hair Loss
50 participants used a helmet-shaped low-level light device for hair loss and scalp condition in a 2023 clinical trial. The device emitted 630 to 690 nm red light along with 820 to 880 nm and 910 to 970 nm near-infrared light to the crown of the head for 20 minutes daily over 24 weeks, at an irradiance of 1.3 mW/cm², while researchers tracked hair density, hair thickness, scalp redness, and oil production at baseline, 12 weeks, and 24 weeks. Researchers found that hair density and thickness increased significantly after 24 weeks, alongside a reduction in scalp oil production, indicating the device improved both hair appearance and scalp condition.
- Study Type
- Clinical Trial
- Participants
- 50
- Treated Area
- Head
- Wavelength(s)
- 630-690, 820-880, 910-970 nm
- Session Duration
- 20 minutes
- Session Frequency
- 7 per week
- Therapy Duration
- 168 days
Study Title: Assessment of Effects of Low-Level Light Therapy on Scalp Condition and Hair Growth.
Review Called Light Therapy Safe and Effective for Hair Loss
This 2021 review examined photobiomodulation, also called low-level laser or light therapy, as a treatment for hair loss. The devices covered included wearable caps, helmets, and combs using wavelengths from about 401 to 2400 nm, spanning blue through infrared, in sessions of roughly 5 to 30 minutes over treatment courses of 54 to 540 days, at irradiances of about 2.5 to 41 mW/cm², an energy of 3 J, and doses around 4 J/cm². According to the review, 1 cited trial reported a significant increase in mean terminal hair density of 43.2 hairs/cm² compared with a sham-treated group, and the review concluded overall that this therapy is safe and potentially effective, whether used alone or alongside standard treatments.
- Study Type
- Review
- Treated Area
- Hair
- Wavelength(s)
- 401-411, 450, 600-2400, 620, 630, 630-660, 640-660, 650-670, 650, 655, 660 nm
- Session Duration
- 8-15 minutes, 5-7 minutes, 5 minutes, 6 minutes, 7 minutes, 10 minutes, 15 minutes, 18 minutes, 20 minutes, 25 minutes, 30 minutes
- Therapy Duration
- 54-540 days
Study Title: Photobiomodulation for the management of hair loss.
Consumer Interest in Light Therapy for Hair Loss Kept Rising
Comparing worldwide Google search trends against physician prescribing surveys, an observational study published in 2021 tracked interest in nonsurgical hair loss treatments, including low-level laser therapy at 650 nm. Researchers compared search trends for hair loss products from 2004 to 2020 against prescribing surveys of hair restoration physicians from 2004 to 2019. Interest in low-level laser therapy appeared to grow over the period, with prescriptions and searches rising further after government regulation announcements, though minoxidil and finasteride remained the most prescribed and most searched treatments.
- Study Type
- Observational Study
- Treated Area
- Head
- Wavelength(s)
- 650 nm
Study Title: The shifting preferences of patients and physicians in nonsurgical hair loss treatment.
Low-Level Laser Device Showed No Clear Benefit for Hair Loss
A clinical trial published in 2009 tested whether low-level laser therapy could enhance hair growth in people with hair loss. 7 participants received light at 650 nm and a broader 650 to 900 nm range, 2 times per week for 20 minutes per session, over 3 to 6 months, at a power of 5 mW, with hair counts and shaft thickness measured through a magnified examination of the scalp at baseline, 3 months, and 6 months. The trial found average increases in terminal hair count and shaft thickness alongside a drop in fine, colorless hair, but none of these changes reached statistical significance, and blinded review of the photographs did not show an improvement in hair density or thickness. The authors suggested this therapy might still help patients who do not respond to standard treatments, though larger controlled studies are needed to confirm any benefit.
- Study Type
- Clinical Trial
- Participants
- 7
- Treated Area
- Head
- Wavelength(s)
- 650, 650-900 nm
- Session Duration
- 20 minutes
- Session Frequency
- 2 per week
- Therapy Duration
- 90-180 days
Study Title: The use of low-level light for hair growth: part I.
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: Aug 10, 2026