LLLT and LED Therapy Across Alopecia Types: Perez 2024 Research Summary
This is a plain-language summary of the original published research. We do not add conclusions or opinions of our own. This is not medical advice — consult a certified healthcare practitioner before making any decision.
Original research published in Dermatologic Surgery, 2024
Low-Level Laser and LED Therapy in Alopecia: A Systematic Review and Meta-Analysis
Study conclusion
This study combined results from 38 studies covering 3,098 patients across multiple types of hair loss. For people with pattern hair loss caused by genetics and hormones, red light therapy significantly increased hair density compared to placebo. Results were stronger in longer treatment periods. Evidence for other hair loss types was too limited to analyse statistically.
Strength of evidence
This was a systematic review and meta-analysis combining 38 studies — the largest review of its kind for this treatment. The score is not higher because the included studies showed very high variability in results (I² above 80%), and most patients in the review had only one type of hair loss, limiting conclusions for other types.
Who it applies to
Who was studied
Adults with pattern hair loss caused by genetics and hormones (2,930 of the 3,098 patients). Smaller numbers of patients with other hair loss types were included: immune-related patchy hair loss (50 patients), hair loss from temporary shedding known as telogen effluvium (17 patients), chemotherapy-related hair loss (32 patients), and scarring hair loss (49 patients).
Who was NOT studied
Children and teenagers. People using red light therapy alongside other treatments — all included studies compared red light therapy against placebo only.
What to look for when shopping
All devices in this study were used for 4 to 26 weeks. Studies running longer than 20 weeks showed stronger results than shorter studies. Both laser and LED devices were included.
What research cannot help you decide
Whether it works for immune-related patchy hair loss, temporary shedding, chemotherapy hair loss, or scarring hair loss. The study could not statistically analyse these groups due to limited data. Which specific device or brand works best.
Key findings
- People with pattern hair loss grew significantly more hair with red light therapy than with placebo across all included studies
- Studies running longer than 20 weeks showed a stronger result (effect size 1.44) than studies under 20 weeks (effect size 1.14)
- Both laser and LED devices were included and both showed significant results
- For hair loss types other than pattern hair loss, the data was too limited to draw conclusions
- 94.5% of the 3,098 patients in this review had pattern hair loss — findings apply most reliably to this group
What they did
Researchers searched three major medical databases for all studies testing red light therapy (laser or LED) against a placebo in patients diagnosed with any type of hair loss. They found 38 qualifying studies covering 3,098 patients. The primary outcome was the change in hair density before and after treatment compared to placebo. Results from pattern hair loss studies were combined statistically. Results from other hair loss types were reported individually because there were too few studies to pool.
What they found
| Comparison | Result | Significant? |
|---|---|---|
| Red light therapy vs placebo — pattern hair loss, under 20 weeks | People grew more hair than the placebo group. The result was large (effect size 1.14). | Yes |
| Red light therapy vs placebo — pattern hair loss, over 20 weeks | People grew more hair than the placebo group. The result was larger than the under-20-week group (effect size 1.44). | Yes |
| Red light therapy — immune-related patchy hair loss (5 studies) | Individual studies reported positive results but there were too few to combine into one overall number. | No |
| Red light therapy — other hair loss types | Individual studies reported positive results but there were too few to combine into one overall number. | No |
What this study does not show
- 1.Whether results last after stopping. The review did not track what happened after treatment ended.
- 2.Whether it works for immune-related patchy hair loss, chemotherapy hair loss, or temporary shedding. Too few studies existed to draw conclusions for these groups.
- 3.Which device type, wavelength, or session schedule is most effective. The review did not compare these variables.
- 4.Whether laser and LED devices perform differently. Both were included but not compared head to head.
- 5.Whether results differ by age, sex, or severity of hair loss within the pattern hair loss group.
Limitations
- 1.Very high variability across the pattern hair loss studies (I² above 80%), meaning the included studies differed substantially in how they were designed and what they found.
- 2.Only 5 to 7 studies were available for non-pattern hair loss types — too few for reliable statistical conclusions.
- 3.The review did not separate results by device type, wavelength, or treatment protocol.
- 4.Full text was behind a paywall — only the abstract was accessible for this summary.
- 5.Some included studies may have used different definitions of hair density, making direct comparison harder.
Who funded it
No funding source was declared for this review. The authors are affiliated with the University of Miami Miller School of Medicine. No conflicts of interest were reported.
Used in these articles
Links added as fact-checks and articles citing this study are published.