Minoxidil —
Longer Growth, Not A DHT Blocker

Minoxidil was first developed as an oral medicine for high blood pressure, and extra hair growth was noticed as a side effect. On the scalp, an enzyme inside the follicle turns it into minoxidil sulphate, the active form.

It is thought to open potassium channels, improve blood flow around the follicle, lengthen the growth phase and let shrunken follicles make a thicker hair. It does nothing to DHT, the hormone behind pattern thinning.

Placebo-controlled studies in men and women with androgenetic alopecia support it, and dermatology guidance lists it as a first-line option. Some regrow hair; many more see thinning slow and hold. Response varies, partly with how active that follicle enzyme is.

Evidence for other kinds of hair loss is thinner, so the cause is confirmed first: see male hair loss and sudden shedding.

The solution or foam goes onto the scalp every day. An early shed is common (see the questions below), and results take months.

The benefit lasts only while it is used: after stopping, the hair it was supporting is lost again over the following months. How the tablet compares with the scalp form, and how it is monitored, is set out under hair loss medications.

• Pregnancy and breastfeeding: not used.
• An irritated, sunburnt or broken scalp.
• Heart conditions or low blood pressure: check with a doctor first.

Itching, flaking or dermatitis can come from the propylene glycol in some solutions, and a foam may suit people who react. Product that runs onto the forehead can encourage fine facial hair, reported more often in women.

Topical minoxidil products are registered medicines, generally sold in pharmacies; the category can depend on strength. Cosmetic hair tonics may not contain it, yet the HSA has found undeclared minoxidil in some. Oral minoxidil is prescription-only.