Masks, bond repair and scalp serums condition damaged hair. For thinning, only minoxidil (and prescription options) has strong trial evidence.
This shelf mixes two different kinds of product. Hair-shaft treatments (masks, bond-repair treatments, leave-in serums and oils) aim at bleached, heat-damaged or dry hair. They are intensive conditioners: they coat and smooth, and bond-building products aim to re-link some broken bonds inside the shaft. They change how hair looks, feels and breaks, not how it grows.
Scalp and regrowth treatments aim at thinning. Here the evidence is narrow: topical minoxidil is the non-prescription first-line option for pattern hair loss in men and women, and oral finasteride is a prescription option for men. Most 'growth serums' use caffeine, biotin, peptides or plant extracts without controlled evidence; rosemary oil has one small trial. Name the type of hair loss first; the hair lesson covers how.
For regrowth, the evidence is strong but narrow: 5% topical minoxidil beat 2% and placebo in a 48-week trial of 393 men, and finasteride increased hair counts over two years in 1,553 men. The rosemary-oil claim rests on one small trial against 2% minoxidil with no placebo. For masks and bond repair, independent trials are largely absent; benefits are cosmetic and measured in the lab. A large cohort linked frequent chemical straightener use with higher uterine cancer rates, an observational finding.
393 men with pattern hair loss used 5% minoxidil, 2% minoxidil or placebo twice daily for 48 weeks. 5% was superior to both, with 45% more regrowth than 2% and an earlier response, but more itching and irritation.
In two one-year trials of 1,553 men, extended to a second year, finasteride 1 mg daily increased hair counts versus placebo (107 hairs at 1 year and 138 at 2 years in a 1-inch circle), while placebo users kept losing hair. The trials were run by the manufacturer.
100 people with pattern hair loss used rosemary oil or 2% minoxidil for six months. Both groups had more hairs at six months with no difference between them; scalp itching was more frequent with minoxidil.
Among 33,947 women followed for about 11 years, using hair straighteners in the prior year was associated with higher uterine cancer rates (HR 1.80), and frequent use more so (HR 2.55). Dyes and perms were not associated.