THE CURE INDEX
Helio Cure's evidence score based on human clinical trials for red light therapy.
Hyperpigmentation is a condition in which patches of skin turn darker than the skin around them.
The CURE Index scored this condition 98 out of 100, indicating strong confidence. That score is based on a review of 6 human studies covering 229 participants, which found red light therapy effective for hyperpigmentation.
Red light therapy may reduce the depth of color in affected patches and make the surrounding skin tone look more uniform.
The evidence leans observational, with 4 observational studies alongside 1 randomized controlled trial and 1 clinical trial. 5 studies reported effective outcomes and 1 reported a partially effective outcome.
830 nm was the most cited wavelength within a tested range of 308 nm to 905 nm. Sessions ran from 1 minute to 120 minutes, 2 to 12 times per week, across courses of 9 to 42 days.
EVIDENCE AT A GLANCE
The numbers behind the verdict.
MOST CITED WAVELENGTH
The wavelength appearing most often in studies that showed benefit for hyperpigmentation.
830 nmTREATMENT PROTOCOL RANGES
The lowest and highest values used across hyperpigmentation studies.
| PARAMETER | RANGE |
|---|---|
| Wavelength | 308-905 nm |
| Session Duration | 60 seconds-120 minutes |
| Session Frequency | 2-12 per week |
| Therapy Duration | 9-42 days |
Note: We have excluded meta-analyses and reviews from scoring, but the list of human studies below contains them for your reference.
7 Human Studies on Red Light Therapy for Hyperpigmentation
Freckles and Age Spots Lightened After 660 nm Laser Sessions
Among 2 Syrian women aged 34 and 49 with lighter skin tones, a 2025 observational study tested low-level laser therapy (LLLT) for facial pigmentation. 1 had freckles, and the other had age spots, and both received 12 sessions of continuous 660 nm red diode laser light at 15.6 mW/cm², 5.6 J/cm², and 500 mW, in 6-minute sessions over 42 days. Pigmentation appeared to lighten from the fourth session onwards, with the skin looking clearer and the wrinkles finer by the eighth, and improvement appeared to continue to the twelfth. No negative effects were reported, and the pigmentation did not return over a year of monthly follow-up.
- Study Type
- Observational Study
- Participants
- 2
- Treated Area
- Face
- Wavelength(s)
- 660 nm
- Session Duration
- 6 minutes
- Session Frequency
- 12 per week
- Therapy Duration
- 42 days
- Study Scope
- Ephelides
Study Title: Low-Level Laser Therapy as an Effective Intervention for Facial Pigmentation: A Case Report of Ephelides and Lentigines in Syrian Women.
Pilot Study Found 830 nm LED Reduced Redness and Pigmentation
10 healthy volunteers took part in a 2025 observational study of LED treatment for the redness and darkening left behind after inflammation. Redness and pigmentation were first triggered on the thigh with 308 nm ultraviolet light at 225 or 270 mJ/cm², and each volunteer then received both a treatment course and a prevention course, using 830 nm LED at 60 J/cm² and 590 nm LED at 20 J/cm² on 5 days across the study. Researchers found that when used as treatment, 830 nm light produced a smaller rise in both redness and pigment than the untreated control, while 590 nm did not differ from control on either measure. Used beforehand as prevention, both wavelengths produced a smaller rise in redness than the control, at 9.85 and 12.50 against 19.90, and did not differ from each other.
- Study Type
- Observational Study
- Participants
- 10
- Treated Area
- Leg
- Wavelength(s)
- 308, 590, 830 nm
- Session Frequency
- 5 per week
- Therapy Duration
- 9 days
Study Title: The Therapeutic and Preventive Effects of Light-Emitting Diode (LED) for Post-Inflammatory Erythema and Hyperpigmentation: A Pilot Study.
More Skin Pigment Meant Less Red and Infrared Light Passed
Whether the amount of pigment in the skin changes how far light travels was tested in a 2024 observational study of 660- and 830 nm laser light. 30 young adults of both sexes in Brazil were split into 2 groups by a standard measure of skin pigment, and light was passed through the back of the elbow and through the heel tendon, with a set of 5 sensors recording how much came out the other side. Light at 830 nm appeared to pass through skin more readily than light at 660 nm, and more pigment was associated with less light getting through at both wavelengths. Light spread about 14 mm at 660 nm in the higher-pigment group versus 21 mm in the lower-pigment group, and about 20 mm versus 26 mm at 830 nm.
- Study Type
- Observational Study
- Participants
- 30
- Treated Area
- Elbow, Heel/Ankle
- Wavelength(s)
- 660, 830 nm
Study Title: In vivo attenuation profile of 660 nm and 830 nm wavelengths on human elbow skin and calcaneus tendon of different phototypes.
81% Responded Well to Laser Therapy for Dark Under-Eye Circles
Across 10 clinical trials published between 1990 and 2018, a 2021 systematic review examined laser treatment for dark circles under the eyes. The reviewed trials each enrolled between 8 and 30 patients, with a mean age of 36.6 years and only 4 men among them, and used a range of high-power lasers including carbon dioxide, Q-switched Alexandrite, Er:YAG, and long-pulse Nd:YAG at 694.3, 1064, and 10600 nm. According to the review, 45.3% of patients showed a good response and a further 35.9% an excellent one, while 2.76% responded poorly. 76.4% of patients said they were satisfied with the result.
- Study Type
- Review
- Treated Area
- Skin
- Wavelength(s)
- 694.3, 1064, 10600 nm
- Session Frequency
- 1, 6 per week
- Therapy Duration
- 120-180 days
- Study Scope
- Periorbital Hyperpigmentation, Infraorbital Hyperpigmentation
Study Title: Effects of laser therapy on periorbital hyperpigmentation: a systematic review on current studies.
Darker Skin Tolerated Less Red Light and Showed More Pigmentation
A dose-escalation design raised the light dose group by group until side effects appeared, across 2 single-blind randomized controlled trials reported in 2020. 115 healthy adults received either 633 nm LED red light or a matched mock device on the inner forearm, 3 times a week for 21 days at 87.2 mW/cm², with doses running from 160 to 640 J/cm² and sessions from 30 to 120 minutes. The highest dose that could be given safely was 320 J/cm² for people with darker skin and 480 J/cm² for non-Hispanic Caucasian participants, with blistering and lasting redness setting the ceiling in each case. Darkening of the treated skin was significantly more common after red light than after the mock device in both trials, and was more pronounced in darker skin, the researchers reported. No serious side effects occurred, and all reactions had settled within 3 months.
- Study Type
- Randomized Controlled Trial
- Participants
- 115
- Treated Area
- Arm
- Wavelength(s)
- 627-639 nm
- Distance
- 0.197 inches
- Session Duration
- 30 minutes, 120 minutes
- Session Frequency
- 3 per week
- Therapy Duration
- 21 days
Study Title: Safety of light emitting diode-red light on human skin: Two randomized controlled trials.
Phototherapy Did Not Heat Skin at Any Pigmentation Level
No rise in skin temperature followed treatment at any skin color, in a 2015 observational study of combined super-pulsed laser and LED phototherapy. 42 healthy adults in Brazil, grouped by skin color on a standard scale, received light from a cluster holding four 905 nm super-pulsed laser diodes pulsed at 250 Hz, four 875 nm infrared diodes and four 640 nm LEDs, at doses of 0, 10, 30 and 50 J delivered over 60 seconds, 76 seconds, 3.8 minutes and 6.33 minutes. Surface temperature was tracked with a camera that measures heat during the last 5 seconds of each dose and for 1 minute afterward. The authors concluded that these doses can be used at any level of skin pigmentation without concern about excessive tissue heating.
- Study Type
- Observational Study
- Participants
- 42
- Treated Area
- Skin
- Wavelength(s)
- 640, 875, 905 nm
- Session Duration
- 60 seconds, 76 seconds, 3.8 minutes, 6.33 minutes
Study Title: The thermal impact of phototherapy with concurrent super-pulsed lasers and red and infrared LEDs on human skin.
No Pigmentation Change From Laser Therapy in a 3-Way Comparison
Comparing low-level laser therapy (LLLT) against electroacupuncture and radiofrequency, a 2016 clinical trial examined facial pigmentation and skin tone in adult women. 30 women aged 30 to 55 in South Korea were split evenly into 3 groups of 10 and given 2 sessions a week for 42 days, with the light group receiving 635 nm at 10 mW in 15-minute sessions. The trial found no significant change in pigmentation in the light group, while the electroacupuncture and radiofrequency groups each showed significant reductions around the eyes and on 1 cheek. Skin tone in the light group did improve significantly on the forehead and around both eyes.
- Study Type
- Clinical Trial
- Participants
- 30
- Treated Area
- Face
- Wavelength(s)
- 635 nm
- Session Duration
- 15 minutes
- Session Frequency
- 2 per week
- Therapy Duration
- 42 days
Study Title: Effects of low-level laser therapy, electroacupuncture, and radiofrequency on the pigmentation and skin tone of adult women.
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: Oct 17, 2026