Regaine is an over‑the‑counter topical treatment containing minoxidil, available as a foam or solution (typically 2 % for women, 5 % for men). The exact mechanism isn’t fully known, but it’s believed to widen blood vessels and open potassium channels, increasing blood flow, oxygen, and nutrients to hair follicles, thereby stimulating regrowth.

Men: Extra strength 5 % foam and solution, indicated for hereditary hair loss in men 18–65.
Women: Regular strength 2 % solution or once‑a‑day 5 % foam.

Solution: Apply 1 mL twice daily directly to the scalp using the dropper, then massage gently. Don’t use more than 2 mL a day.
Foam: Apply to dry, healthy scalp. Leave it on—don’t blow‑dry, as it can reduce effectiveness.
You typically need at least 4 months (twice‑daily) or 16 weeks (women's once‑a‑day foam) to see regrowth.
Stopping treatment usually leads to relapse within 3–4 months.

Men: Up to 90 % reported retention or regrowth after 16 weeks using 5 % foam.

Women: Over 80 % had visible regrowth with once‑a‑day 5 % foam. 
Clinical evidence shows:

5 % solution can regrow hair in 3 of 5 men after 48 weeks, with results sometimes visible at 8 weeks.
2 % solution may show results in about 16 weeks.

Common side effects include:

Scalp irritation, itching, dry skin, flaking. 
Initial increased shedding (often temporary).
Rare but serious risks:
Systemic absorption may cause unwanted hair elsewhere.
There have been rare cases of excessive hair growth (hypertrichosis) in babies exposed to minoxidil through contact. 

Yes. Experts and users report improved experience when combining:

Regaine with Minoxidil
Supplements like biotin, caffeine, and kopexil for follicle support and scalp health.
Use of Nizoral shampoo to control dandruff and optimise the scalp environment.
Many dermatologists recommend starting with minoxidil as the first-line therapy.