What Is Low-Level Laser Therapy (LLLT) for Hair?

Low-level laser therapy (LLLT) is the medical name for the red-light treatment used by at-home hair devices like iRestore, Capillus, Kiierr, HairMax and Theradome. "Low-level" means the light is far too weak to heat, cut or damage tissue. You feel nothing during a session except, sometimes, mild warmth from the device itself.

What it treats

Home LLLT devices are FDA-cleared for androgenetic alopecia — the common, genetic form of thinning that shows up as a receding hairline or thinning crown in men and a widening part in women. They are not cleared for, and are not expected to help, hair loss from thyroid disease, iron deficiency, alopecia areata or scarring conditions.

The three ingredients

1. Wavelength. Home devices use red light between roughly 630 and 680 nm. See wavelengths explained.
2. Light source. Lasers, LEDs or both. See lasers vs LEDs.
3. Dose. How long and how often you treat. Each device's schedule is set to deliver a studied dose; skipping sessions lowers it.

What results look like

Clinical trials against inactive "sham" devices have shown modest increases in hair density over 16–26 weeks for people with pattern hair loss. ADD CITATION Real-world results vary from person to person, take 4–6 months to become visible, and fade gradually if treatment stops.

Is it safe?

LLLT has a strong safety record in trials; the most common complaints are mild scalp dryness or itching. People with light-sensitive conditions or on light-sensitising medication should talk to a doctor first.

Where to start

Our rankings hub compares the five best-known FDA-cleared devices. For the full mechanism, read how laser hair therapy works.