Caffeine

What it does

Caffeine shampoos and tonics are sold for thinning hair. The research behind them:

• Lab studies: caffeine counteracted the growth-slowing effect of testosterone on hair follicles grown in a dish (from biopsies).
• Absorption: in a small study, caffeine from a shampoo got into hair follicles within two minutes.
• People: an open-label trial of 210 men, funded by a caffeine-product maker, concluded a caffeine liquid was "not inferior" to 5% minoxidil — but participants knew which product they were using, and the outcome was the share of growing hairs rather than hair count. A 2025 review found few studies of caffeine on its own.

Cautions

• Caffeine products are cosmetics, not licensed treatments. If you're losing hair, find out why first — see a GP for sudden, patchy or worrying hair loss.

How strong is the evidence?

Evidence: Limited

Small or early studies only — promising at best.

Mostly laboratory work and a small number of company-funded trials. Rated limited.

UK rules and availability

A cosmetic ingredient in the UK.

Products on this site that list it

• The Ordinary Multi-Peptide Serum for Hair Density

Not medical advice. This guide is general information from the sources listed, not a diagnosis or a substitute for a pharmacist, GP or dermatologist. If you are worried, or symptoms are severe or not improving, get advice. Read our health information policy.

Sources

1. Fischer TW et al. Effect of caffeine and testosterone on the proliferation of human hair follicles in vitro. Int J Dermatol 2007 pubmed.ncbi.nlm.nih.gov
2. Otberg N et al. Follicular penetration of topically applied caffeine via a shampoo formulation. Skin Pharmacol Physiol 2007 pubmed.ncbi.nlm.nih.gov
3. Dhurat R et al. Caffeine-based topical liquid versus minoxidil 5% in male androgenetic alopecia. Skin Pharmacol Physiol 2017 pmc.ncbi.nlm.nih.gov
4. Gupta AK et al. Do non-prescription products help in managing androgenic alopecia? Skin Appendage Disord 2025 pmc.ncbi.nlm.nih.gov