Can Minoxidil Cause Unwanted Body Hair Growth?
Yes, minoxidil can cause unwanted hair growth on the face and other parts of the body, though this side effect is relatively uncommon and reversible upon discontinuation.
Incidence and Clinical Evidence
Hypertrichosis (unwanted facial and body hair growth) affects approximately 15% of patients on low-dose oral minoxidil 1
The FDA drug label explicitly warns that unwanted facial hair growth can occur with topical minoxidil use, advising patients to stop use if this develops 2
This side effect is described as rare and reversible—if caused by minoxidil, the unwanted hair will gradually disappear after stopping treatment 2
Mechanism and Historical Context
Minoxidil was originally developed as an oral antihypertensive medication, and hypertrichosis (increased growth or darkening of fine body hairs) was discovered as a side effect, which led to the development of topical formulations for treating hair loss 3
The drug can promote hair growth in areas beyond the intended application site through systemic absorption or inadvertent transfer 3
Risk Mitigation Strategies
The FDA provides specific recommendations to minimize unwanted hair growth 2:
- Limit application strictly to the scalp and avoid contact with other body areas
- Wash hands thoroughly with soap and water immediately after application if using fingers to apply
- Allow adequate drying time (2-4 hours) before going to bed after nighttime application to prevent transfer to pillows and facial contact
Important Caveats
Women appear to be at higher risk for facial hair growth, which is one reason the 5% formulation is not recommended for women 2
The effect is dose-dependent and application-site dependent—proper technique significantly reduces risk 2
Any unwanted hair growth that develops should prompt discontinuation, with resolution expected over time 2