Protocol · Light
Red light therapy (photobiomodulation)
B-
Headline grade
Increases hair density in androgenetic alopecia
Evidence type: Randomized trials
The graded dose: Red and near-infrared light (about 630 to 670 nm red, 810 to 850 nm near-infrared) applied to the target area; the skin trial behind the headline outcome used polychromatic 570 to 850 nm light, 2 sessions per week for 30 sessions. Frequency in the evidence: 3 sessions per week. Program length in the evidence: 8 to 15 weeks in the trials behind the graded outcomes. The grade attaches to this dose; below it, the grade does not apply.
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Time cost
70 minutes / week
3 sessions x 20 minutes session time = 60, counted 70 with setup overhead at home; the skin trial pattern (2 per week) counts about 50.
Dollar cost
About $25 / month
Home panel $300 to $1,500 one-time (about $10 to $45 a month amortized over three years); clinic or studio sessions $25 to $75 each (basis: device-amortized)
Every claim, graded
Each outcome this protocol is claimed to deliver carries its own grade and its own kind of evidence. A strong secondary outcome never launders a weak popular claim: the popular claim prints at its own grade, next to the headline.
Outcomes at a glance
Improves skin appearance and collagen density (the popular anti-aging claim)
Popular claim, graded on its own evidenceIncreases hair density in androgenetic alopecia
Improves exercise performance and speeds muscle recovery
Slows aging or extends healthspan systemically
Bar length is the outcome's evidence grade on the house scale: A is 4.0 points, B is 3.0, C is 2.0, D is 1.0. The table below carries the evidence type and what the data show for each row.
| Claim | Grade | Evidence | What the data show |
|---|---|---|---|
| Improves skin appearance and collagen density (the popular anti-aging claim)Popular claim, graded on its own evidence | C+ | rctRandomized trials | In the largest controlled trial (Wunsch and Matuschka 2014, n=136, 30 sessions over about 15 weeks), treated groups showed significantly improved skin complexion and reduced roughness on blinded photo evaluation and increased intradermal collagen density on ultrasound versus controls. Effects were measurable, not dramatic, and smaller supportive trials agree in direction.Wunsch A, Matuschka K. A controlled trial to determine the efficacy of red and near-infrared light treatment in patient satisfaction, reduction of fine lines, wrinkles, skin roughness, and intradermal collagen density increase. Photomedicine and Laser Surgery, 2014. |
| Increases hair density in androgenetic alopecia | B- | rctRandomized trials | A meta-analysis of 11 double-blind randomized sham-controlled trials (Liu et al., Lasers in Medical Science, 2019) found a significant increase in hair density versus sham (SMD 1.316, 95% CI 0.993 to 1.639), across comb and helmet devices and both sexes; the review notes heterogeneity between trials and much of the trial base is device-maker run.Liu KH et al. Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a systematic review and meta-analysis of randomized controlled trials. Lasers in Medical Science, 2019 (PMID 30706177). |
| Improves exercise performance and speeds muscle recovery | C+ | mixedMixed evidence | A systematic review and meta-analysis of randomized trials (Leal-Junior et al., 2015) found photobiomodulation applied before exercise improved repetition counts and time to exhaustion and lowered some muscle-damage markers. Most trials used lasers or LED arrays applied directly to the muscle at measured doses; full-body panels used at a distance may deliver a different dose, so the transfer to consumer panels is unproven.Leal-Junior ECP et al. Effect of phototherapy (low-level laser therapy and light-emitting diode therapy) on exercise performance and markers of exercise recovery: a systematic review with meta-analysis. Lasers in Medical Science, 2015. |
| Slows aging or extends healthspan systemically | D | mechanisticMechanism only | No human trial measures an aging or healthspan outcome for red light therapy. The claim rests on mitochondrial mechanism work and animal data; under the protocol rubric, mechanism alone caps at D+ and an unmeasured popular claim grades below it.Protocol grading rubric section 1.3 (mechanism cap); absence of any human outcome trial as of 2026-10-28. |
Dose and response
Only the studied patterns carry outcome data: skin at 2 sessions per week over about 15 weeks, hair devices at low weekly frequency (the meta-analysis found low-frequency treatment at least as effective as high-frequency). Daily full-body panel use at consumer distances is the marketed pattern, not the studied one, and does not inherit these grades.
Equipment that can deliver this dose: Home device.
Harms and cautions
Harms live in this ledger, not inside the grade: the grade is evidence for the claimed outcomes in the studied population.
Medication interactions
No medication classes are flagged in this graded record.
Photosensitivity: light can interact with photosensitizing medications and conditions; people on photosensitizers (certain antibiotics, isotretinoin, some diuretics) should clear use with their prescriber first. caution
users on photosensitizing medication
Source: Protocol rubric List B pattern (bright light with photosensitizing medication); named here as a harm entry only, no interaction is presented in the builder until it is sourced into the interaction data.
Goal conflicts and timing
No goal conflicts in this record.
The studied patterns are the dose: skin at 2 sessions a week over about 15 weeks, hair devices at low weekly frequency. Daily full-body panel use at consumer distances is the marketed pattern, not the studied one.
Population exclusions and other cautions
Eye exposure: bright red and near-infrared arrays should not be stared into; use the eye protection devices ship with, especially at close range. caution
all users
Source: Device safety guidance across the trial literature; standard photobiomodulation practice.
Active malignancy at the treatment site: photobiomodulation is used in oncology support care under supervision, but self-treating over a known or suspected skin lesion is outside the evidence; suspicious lesions belong to a dermatologist. caution
users with skin lesions
Source: Glass GE. Photobiomodulation: a systematic review of the oncologic safety of low-level light therapy for aesthetic skin rejuvenation, 2023 (no clinical evidence of new or recurrent cancer from skin PBM; supervision framing retained as caution).
Can you measure it yourself?
No self-experiment is offered for this record's headline outcomes. Graded under research/protocol-grading-rubric.md. Distinct from the graded bright-light-therapy record (10,000 lux white light for mood and circadian indications); the two interventions share the light class and nothing else.
Goals served
None at the serving floor
Derived from outcomes grading B- or better, never hand-assigned.
Experience gate
beginner and up (gated for safety)
Applicability
targeted
Applies to a specific goal or population, not broadly.
Grades are research summaries, not medical advice. Decisions about your own stack belong with your clinician.
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Frequently asked questions
What grade does Red light therapy (photobiomodulation) get?
At the studied dose (Red and near-infrared light (about 630 to 670 nm red, 810 to 850 nm near-infrared) applied to the target area; the skin trial behind the headline outcome used polychromatic 570 to 850 nm light, 2 sessions per week for 30 sessions), Red light therapy (photobiomodulation) grades B- for increases hair density in androgenetic alopecia, on randomized trials. The grade attaches to that dose; below it, the grade does not apply.
How much time does Red light therapy (photobiomodulation) take each week?
At the graded dose, 70 minutes per week, counted as session time plus standard overhead, travel excluded. Dollar cost: Home panel $300 to $1,500 one-time (about $10 to $45 a month amortized over three years); clinic or studio sessions $25 to $75 each.
Does Red light therapy (photobiomodulation) deliver its most popular claim?
The popular claim (Improves skin appearance and collagen density) grades C+. In the largest controlled trial (Wunsch and Matuschka 2014, n=136, 30 sessions over about 15 weeks), treated groups showed significantly improved skin complexion and reduced roughness on blinded photo evaluation and increased intradermal collagen density on ultrasound versus controls. Effects were measurable, not dramatic, and smaller supportive trials agree in direction.
Sources
- Wunsch A, Matuschka K. Photomedicine and Laser Surgery, 2014 (skin RCT, n=136). (2014)
- Liu KH et al. Lasers in Medical Science, 2019 (alopecia meta-analysis, 11 double-blind RCTs). (2019)
- Leal-Junior ECP et al. Lasers in Medical Science, 2015 (exercise performance and recovery meta-analysis). (2015)
Changelog
Last reviewed October 29, 2026
- 2026-10-28|Initial grading (Research draft): headline B- on hair density; skin C+; performance and recovery C+; systemic longevity claim D. Draft pending Growth integration.
- 2026-10-29|Integrated into the live library by Growth (2026-10-29): the draft status is resolved to live, and the two builder fields the draft did not carry were completed from the record itself (levelGate safety/beginner, the house pattern for self-administered light protocols; scheduling restating the doseSpec and doseResponse patterns verbatim in substance). Flagged to Research for verification the same hour. No graded field changed.