MINOXIDIL

A medication primarily used to treat hair loss, not typically a cosmetic ingredient. Minoxidil is a potassium channel opener (K_ATP channels) that, when applied topically, stimulates hair growth by causing vasodilation, which improves blood flow to hair follicles. It is believed to prolong the anagen (growth) phase of the hair cycle and shorten the telogen (resting) phase, leading to thicker and longer hair. Its active metabolite, minoxidil sulfate, likely plays a key role, potentially by stimulating dermal papilla cells and increasing vascular endothelial growth factor (VEGF) expression.

Minoxidil is an FDA-approved OTC drug for androgenetic alopecia. Common side effects include local irritation, dryness, itching, and hypertrichosis (unwanted hair growth). Systemic absorption is minimal but can rarely lead to cardiovascular effects like hypotension or tachycardia. It is generally well-tolerated when used as directed.

Look for products with 2-5% (most formulas for men use 5% and for women use 2-5%) for clinical efficacy.