Mahidol University trial: 3% minoxidil raised facial hair density 15–17% in 69 transgender men

Researchers at Mahidol University in Bangkok, Thailand, report that topical 3% minoxidil increased facial hair density in transgender men receiving gender-affirming hormone therapy, according to sciencealert.com. sciencealert.comsciencealert.comsciencealert.comOpen source ↗ The randomized, double-blind, placebo-controlled trial included 69 participants and is published in The Journal of Dermatological Treatment.

Thirty-four participants applied 3% minoxidil to the face twice daily for 12 weeks, while 35 used a placebo. The study was led by dermatologist Kantarat Wattanawinitchai.

Trial results and safety

At 8 weeks, the minoxidil group had denser and thicker facial hair than the placebo group. At 12 weeks, mustache density in this group had increased by roughly 17% and beard density by 15% from baseline. Many participants also reported higher quality of life and satisfaction scores.

Side effects such as itching, red skin and flakiness were minimal, and no serious adverse events were reported. sciencealert.comsciencealert.comsciencealert.comOpen source ↗ Participants' blood pressure remained stable throughout. Minoxidil is a blood vessel dilator, so if enough of it is absorbed it could in theory cause dizziness, low blood pressure or rapid heartbeat. The authors call the observed safety profile reassuring given these theoretical concerns.

Background and limits

Minoxidil was developed in the 1970s as an oral drug for high blood pressure, and it was found to stimulate hair growth. In 1988 the US Food and Drug Administration approved a topical version, marketed as Rogaine, for male-pattern hair loss; approval for female pattern hair loss followed. Topical minoxidil is not approved by the FDA for facial hair in any group.

A 2016 study in cisgender men was the first to show that 3% topical minoxidil improved beard growth compared with a placebo. A case report of identical twins describes greater beard and mustache hair count and density after 16 months in the twin who used 5% minoxidil for over a year.

The new results come from transgender men only, so it is unclear whether they apply to other groups. The authors note that ongoing testosterone therapy may act synergistically with minoxidil. sciencealert.comsciencealert.comsciencealert.comOpen source ↗ They argue that minoxidil should be considered a first-line adjunctive treatment for transgender men whose facial hair development remains incomplete despite adequate testosterone therapy. The American Academy of Dermatology advises consulting a dermatologist first, noting that raw, irritated skin is a common side effect on the face.