How Long Red Light Therapy Studies Lasted

A common question about red light therapy is how long it takes to see a change. Published research cannot answer that for any individual — results in trials vary from person to person and depend on the device, the settings, and the condition studied. What the research can show is how long clinical trials lasted, how many sessions participants received, and when researchers measured outcomes. This article summarizes that information. It is not a prediction of results and is not a recommended treatment schedule.

Why study timelines are not personal timelines

When a trial reports a change "after 4 weeks," that describes the average or measured outcome for that study's participants, using that study's device and protocol, at that time point. Several factors limit how far this can be generalized:

• Protocols vary. Trials differ in wavelength, dose, number of sessions, and session frequency, and reviewers have found it difficult to identify an optimal protocol.¹
• Measurement points are chosen by researchers. A trial that measured outcomes at four weeks does not show whether changes started earlier, continued later, or faded afterward.
• Participants differ. Trials typically enroll specific groups (for example, a defined age range or severity level) that may not reflect the general population.²

Study durations in skin aging research

In trials of red and near-infrared light on wrinkles, roughness, elasticity, and collagen:

• A randomized, sham-controlled split-face study treated participants twice weekly for four weeks and then followed them for three months.³
• A randomized controlled trial of 136 volunteers delivered twice-weekly treatments and measured outcomes after 30 sessions.⁴
• A split-face trial of 137 women measured periocular wrinkle volume after 10 sessions over four weeks.⁵

A 2018 systematic review of LED trials summarized the skin rejuvenation evidence by noting that daily treatment with combined red and near-infrared LED light for 8 to 10 weeks showed the best efficacy for wrinkles among the studies it reviewed.¹ That conclusion describes the protocols used in published studies, which the review graded as a lower level of evidence (grade C).¹

Study durations in acne research

• A 2025 meta-analysis of six randomized trials of at-home LED devices for acne reported that study durations ranged from 2 days to 12 weeks, and that improvement was typically observed after 4 to 12 weeks in those studies.²
• A 2016 Cochrane review of 71 trials of light therapies for acne found that fewer than half assessed outcomes more than eight weeks after the final treatment, leaving long-term effects largely unknown.⁶

What is known about durability

How long any measured changes last after treatment stops is one of the least-studied questions in this field. The Cochrane review noted that long-term effects of light therapy for acne are largely unknown because of short follow-up periods.⁶ In January 2026, Santé.fr, the French government's public health information service, stated that reported effects of LED masks on skin take time to appear and that their durability and long-term side effects are unknown.⁷

Summary

Published trials of red light therapy for skin aging and acne have generally lasted from a few weeks to about three months, with outcomes typically measured after several weeks of repeated sessions. Follow-up after treatment ends is often short or not reported, so the durability of changes remains an open question. These study timelines describe research conditions and should not be read as a forecast of any individual's experience.

Disclaimer

This article is for general informational purposes only and does not constitute medical, legal, or professional advice. It summarizes published research and is not intended to diagnose, treat, cure, or prevent any condition, to recommend a treatment schedule, or to suggest that any device will produce a particular result within any timeframe. Study findings may not apply to any individual. Regulatory clearance of a device does not guarantee its effectiveness. Redlight Ratings is not a medical provider. Anyone with health questions should consult a qualified healthcare professional.

References

1. Jagdeo J, Austin E, Mamalis A, Wong C, Ho D, Siegel DM. Light-emitting diodes in dermatology: A systematic review of randomized controlled trials. Lasers in Surgery and Medicine. 2018;50(6):613-628. https://pmc.ncbi.nlm.nih.gov/articles/PMC6099480/
2. Ershadi S, Barbieri JS. At-home LED devices for the treatment of acne vulgaris: A systematic review and meta-analysis. JAMA Dermatology. 2025;161(5):552-555. https://doi.org/10.1001/jamadermatol.2025.0019
3. Lee SY, Park KH, Choi JW, et al. A prospective, randomized, placebo-controlled, double-blinded, and split-face clinical study on LED phototherapy for skin rejuvenation. Journal of Photochemistry and Photobiology B. 2007;88(1):51-67. https://pubmed.ncbi.nlm.nih.gov/17566756/
4. 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;32(2):93-100. https://pubmed.ncbi.nlm.nih.gov/24286286/
5. Mota LR, Duarte IS, Galache TR, et al. Photobiomodulation reduces periocular wrinkle volume by 30%: A randomized controlled trial. Photobiomodulation, Photomedicine, and Laser Surgery. 2023;41(2):48-56. https://pubmed.ncbi.nlm.nih.gov/36780572/
6. Barbaric J, Abbott R, Posadzki P, et al. Light therapies for acne. Cochrane Database of Systematic Reviews. 2016;9(9):CD007917. https://pubmed.ncbi.nlm.nih.gov/27670126/
7. Santé.fr (Service Public d'Information en Santé, France). Les masques à LED sont-ils efficaces et sûrs ? January 12, 2026. https://www.sante.fr/node/8069061