LLLT Frequency and Device Type for Hair Loss: Liu 2019 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 Lasers in Medical Science, 2019
Comparative effectiveness of low-level laser therapy for adult androgenic alopecia: a system review and meta-analysis of randomized controlled trials
Study conclusion
This study combined results from 11 controlled trials. People with pattern hair loss who used red light therapy devices grew significantly more hair than people using fake devices. Devices used for less than 60 minutes total per week produced stronger results than devices used for more than 60 minutes per week.
Strength of evidence
This was a systematic review combining 11 controlled trials. The score is not higher because the trials used different devices and schedules, and the longest ran only 26 weeks. The core finding is well established. The exact size and duration of benefit are less certain.
Who it applies to
Who was studied
Adults with pattern hair loss caused by genetics and hormones. Both men and women. Hair loss rated between stages II and V on standard medical grading scales.
Who was NOT studied
People with patchy hair loss caused by the immune system. People with scarring on the scalp. People whose hair loss is caused by medication or illness.
What to look for when shopping
All devices in this study were used for at least 16 weeks. Devices used for less than 60 minutes per week produced stronger results. Both comb style and cap or helmet style devices worked.
What research cannot help you decide
Which specific product to buy. Whether your skin tone affects results. What happens after stopping use.
Key findings
- Real devices grew more hair than fake devices across all 11 trials
- People using devices under 60 minutes per week grew about 64% more hair than people using them over 60 minutes per week (both groups still grew more hair than the fake device group)
- Comb style and cap or helmet style devices produced similar results
- Both men and women responded
- Results at 16 weeks and 26 weeks were similar
What they did
Researchers searched three major medical databases for every double-blind controlled trial testing red light therapy against a fake device for pattern hair loss in adults. They found 11 qualifying trials from 8 studies and combined their results. In each trial one group used a real red light therapy device at home. The other group used a fake device that looked identical but produced no light. Neither group knew which device they had. Hair density (the number of hairs per square centimetre) was measured at the start and end of each trial.
What they found
| Comparison | Result | Significant? |
|---|---|---|
| Real device vs fake device | Real devices grew more hair (effect size 1.316, considered large) | Yes |
| Under 60 min/week vs over 60 min/week | Both groups grew more hair than fake. Under 60 min group result was about 64% stronger (1.555 vs 0.949). | Yes |
| Comb type vs helmet or cap type | No meaningful difference | No |
| 16 weeks vs 26 weeks of use | No meaningful difference | No |
| Men and women vs fake device | Both showed significant improvement. No separate numbers reported. | Yes |
What this study does not show
- 1.Whether results last after stopping. The longest trial ran 26 weeks and no trial tracked what happened after people stopped.
- 2.Whether any specific brand works better. No trial compared one product directly against another.
- 3.Which wavelength works best. Devices used wavelengths from 630 to 808nm and the study did not compare them.
- 4.Whether FDA cleared devices are more effective. This review included both cleared and non-cleared devices.
- 5.Whether results differ across skin tones. Skin type was not consistently reported across trials.
Limitations
- 1.The 11 trials used different devices, wavelengths, and schedules. The combined result reflects a wide range of approaches.
- 2.The longest trial ran 26 weeks. What happens after that is unknown.
- 3.The review included both FDA cleared and non-cleared devices.
- 4.The session frequency finding came from a subgroup analysis, which carries less weight than the main result.
- 5.Individual trial sample sizes were small.
- 6.Funding status of the included trials was not reported by the review authors.
Who funded it
No funding source was declared for this review. The authors reported no conflicts of interest.
Used in these articles
Links added as fact-checks and articles citing this study are published.