The growth of human scalp hair mediated by visible red light laser and LED sources in males (2013) and in females (2014). Lanzafame RJ et al. Lasers in Surgery and Medicine.
Why this pair matters
They are randomized, double-blind, sham-device-controlled trials, the strongest common design in consumer phototherapy, run separately in men and women with the same home-use technology, and they measured hair by counting it in a fixed scalp area rather than by asking anyone's opinion.
Design
- Participants: 41 men aged 18–48 (2013 trial); 42 women aged 18–60 (2014 trial), all with pattern hair loss.
- Device: a helmet-form unit combining 655nm laser diodes with LEDs; sham units looked and behaved identically without the therapeutic output.
- Protocol: roughly 25-minute sessions every other day for 16 weeks, at home.
- Endpoint: change in hair counts within a tattooed target area, evaluated blind.
Findings
The male trial reported approximately a 35% increase in hair counts versus sham; the female trial approximately 37%, with the authors reporting no adverse events in either. The agreement between two independently run trials, across sexes, is the result's real strength, single positive trials are common in this field, replicated ones are not.
Limits worth stating
- Both trials were industry-associated, as most device trials are; the sham control and blinding are the defenses against that, not a reason to ignore it.
- Percentage gains in counted density within a small target area are visually subtler than marketing photography implies.
- Findings concern androgenetic (pattern) hair loss specifically, at these parameters, in this device format.
Sources: Lasers Surg Med 2013 (males), DOI: 10.1002/lsm.22173 · Lasers Surg Med 2014 (females), PMID: 25124964