What These Trials Looked At
Androgenetic alopecia — pattern hair loss in both men and women — affects most adults at some point in life. Standard treatment options have remained narrow for decades: topical minoxidil, oral finasteride for men, and surgical hair transplantation for those willing and able. Each works for some patients, none works for all, and many people seek non-pharmacological approaches that fit a daily home routine. In 2013 and 2014 a research team led by Raymond Lanzafame published two carefully matched randomised, double-blind, sham-controlled trials in Lasers in Surgery and Medicine — one in men, one in women — testing whether visible red-light therapy at 655 nm could meaningfully shift hair counts in pattern hair loss.
Both trials used the same intervention and analytic approach. Participants in the active arm received 655 nm red-light therapy via a home-use device, applied at scheduled intervals over a 16-week treatment period. The sham arm used an identical device delivering visually equivalent but biologically inactive light. The primary endpoint was the change in terminal hair count in a tattooed transition-zone region of the scalp, measured by blinded macroscopic and digital image analysis between baseline and 16 weeks.
What They Found
The 2013 trial in 41 men with mild-to-moderate androgenetic alopecia found a 39 percent increase in hair counts in the active group compared with sham at 16 weeks (p < 0.0001). The 2014 trial in 47 women with female-pattern hair loss found a 37 percent increase in hair counts compared with sham at the same time point (p < 0.0001). Across both trials, the active groups showed significant gains while the sham groups remained essentially unchanged.
The closely matched effect sizes in two separate sex cohorts strengthen the result. Independent confirmation across cohorts is one of the cleaner forms of evidence in clinical research, and the consistency between the men’s and women’s trials supports the case that the underlying mechanism — photobiomodulation of dormant or miniaturised hair follicles — is acting independently of sex-specific hormonal background.
What This Means in Context
These two trials sit among the strongest pieces of evidence supporting low-level light therapy for androgenetic alopecia. The design — sham-controlled, blinded outcome assessment, validated tattooed-region measurement — addresses the main biases that have limited earlier hair-regrowth research. The 16-week duration is long enough to capture meaningful follicle response, and the effect sizes are clinically visible rather than statistical curiosities.
What the trials do not establish is durability beyond 16 weeks, head-to-head comparison with minoxidil or finasteride, or the optimal long-term maintenance protocol. Subsequent meta-analyses of FDA-cleared home-use LLLT devices have largely confirmed the direction of the Lanzafame findings, and the field continues to mature.
What It Means for You
If you are dealing with pattern hair loss and are looking for a non-pharmacological option you can use consistently at home, these two trials are part of the clearest body of evidence available that 16 weeks of consistent red-light therapy can produce a measurable, near-40-percent increase in hair counts in the treated region. Photobiomodulation is best understood as one option alongside the standard approaches your dermatologist or trichologist may recommend — and a conversation with the clinician helping you manage hair loss is the right starting point before introducing any new approach.
Citations:
Lanzafame, R.J., Blanche, R.R., Bodian, A.B., Chiacchierini, R.P., Fernandez-Obregon, A., & Kazmirek, E.R. (2013). The growth of human scalp hair mediated by visible red light laser and LED sources in males. Lasers in Surgery and Medicine, 45(8), 487-495. PubMed
Lanzafame, R.J., Blanche, R.R., Chiacchierini, R.P., Kazmirek, E.R., & Sklar, J.A. (2014). The growth of human scalp hair in females using visible red light laser and LED sources. Lasers in Surgery and Medicine, 46(8), 601-607. PubMed
