Caffeine Shampoo and Hair Loss: the Evidence, Trial by Trial

Caffeine shampoo is the most heavily advertised idea in this aisle and one of the thinnest on evidence. There are two trials worth reading, a regulator that read them and was unconvinced, and a 2025 expert consensus that does not recommend caffeine at all. On this site's ten-point scale it scores four, which is the thin band.

The trial everybody quotes, and who paid for it

Dhurat and colleagues ran a randomised, open-label, multicentre non-inferiority study in 210 men with androgenetic alopecia, comparing a caffeine-based 0.2% topical liquid with 5% minoxidil solution over six months. The primary endpoint was the percentage change in the proportion of anagen hairs on a frontal and occipital trichogram. At six months the minoxidil group showed a mean anagen improvement of 11.68% and the caffeine group 10.59%, a difference of 1.09%, and the authors concluded the caffeine liquid should be considered not inferior to minoxidil (Skin Pharmacology and Physiology, 2017).

Two things in that paper are usually left out. The test product was manufactured by Dr. Kurt Wolff, the German company that sells Alpecin; the paper's own acknowledgements thank Dr. Kurt Wolff for funding the study, the randomisation was generated at Dr. Kurt Wolff, and one author is a company employee with another named as a consultant. And the product was a leave-on liquid applied to the scalp, not a shampoo — the trial does not test the thing on the supermarket shelf at all.

That is what a zero on our second question looks like. It is not an accusation of bad faith; company-funded trials can be well run, and this one reports its methods openly. It is a statement about who chose the question, the comparator and the endpoint.

The shampoo trial

Bussoletti, Tolaini and Celleno ran a single-centre, double-blind parallel trial in women with androgenetic alopecia, randomising them to a phyto-caffeine-containing shampoo or a control shampoo for six months. The primary endpoint was the change from baseline in the number of hairs removed by a hair pull test, and the caffeine group had significantly fewer hairs pulled at six months than the control group — a fall of 3.1 hairs against 0.5 (Giornale Italiano di Dermatologia e Venereologia, 2020).

This one does have a control shampoo, which earns the row its two points on the first question. Its weakness is the outcome: a hair pull test counts hairs that come away when a small bundle is tugged, which is a measure of shedding rather than of how much hair is on the head. It scores one out of two on what was counted, where a hair count from a phototrichogram would have scored two.

What the regulator made of the evidence

In 2018 the UK Advertising Standards Authority considered whether an advertisement could say Alpecin caffeine shampoo helps to reduce hair loss. Because the claim was about reducing hair loss rather than curing or preventing it, the bar was robust evidence rather than a medicines licence — the advertiser simply had to substantiate it.

The ASA looked at the studies submitted and found problems: one lacked a control group, one did not relate to the product being advertised, and others had methodological issues. Taking the body of evidence as a whole, it did not consider the claim substantiated, upheld the complaint against Dr Kurt Wolff GmbH on 28 March 2018, and told the company not to state or imply that the product could reduce hair loss unless it held adequate evidence.

The complaint was upheld, and the advertiser was told not to state or imply that their product could reduce hair loss unless they held adequate evidence to support the claim. — Advertising Standards Authority ruling on Dr Kurt Wolff GmbH, 28 March 2018

A regulator's view is not a scientific finding, and an ASA ruling applies to UK advertising rather than to the world. It is still the only time we found a regulator demanding the evidence behind a hair-loss claim on a product in this aisle, and getting an answer it would not accept.

And the expert panels

The 2025 Canadian consensus on androgenetic alopecia, built by eleven physicians assessing forty-five interventions, lists caffeine among the seventeen it does not recommend — and separately lists shampoo and lotion hair care products containing fermented papaya, fermented mangosteen and caffeine among them as well. Four of the paper's listed authors give L'Oréal Canada as their affiliation, which is worth knowing in both directions when reading a list of what is and is not recommended.

So is it worth buying?

If you like the shampoo, it is a shampoo and it will wash your hair. What it does not have is the kind of evidence that would justify paying a premium over a medicated shampoo with a proper hair count behind it. Two actives on this site score higher on the same scale and cost less; the whole ranking is in the best shampoo for hair loss, graded on published evidence.

For the same argument about a product whose evidence is even thinner, read peptide and Redensyl serums, read against their own studies.