Caffeine Shampoo: Ineffective for Combating Hair Loss

A watchdog in the UK ruled in 2018 that there is no evidence that Alpecin Caffeine shampoo can reduce hair loss. Since then, the makers of the product have been banned from claiming or implying that their product can stop hair loss.

In the Netherlands, the ban does not apply and the claim remains unchanged, despite a lack of evidence. In its defence, the manufacturer refers on its website to 12 studies that allegedly prove the effectiveness of caffeine shampoo. The majority of which are funded by the manufacturer and/or carried out by its own employees.

In this article we examine the validity of these studies. We analyse their results and compare them with those of similair research papers to see if their claims hold up.

Caffeine and DHT

Hereditary hair loss is caused by the male androgen DHT (dihydrotestosterone).¹ A hormone produced by the interaction of testosterone and the enzyme 5 alpha-reductase. Hair follicles that come into contact with DHT lose their ability to produce thick and long hair over time. This process takes several years, but eventually leads to what we call androgenetic alopecia, or male pattern hair loss.

Finasteride, a medicine, stops hair loss by reducing the amount of DHT by about 70%.² It does this by inhibiting the 5 alpha-reductase enzyme, causing less testosterone to be converted into DHT. This reduction in DHT is enough to stop hair loss completely in over 80% of the males who take this medicine.

Caffeine however does not and seems rather useless for reducing DHT. In fact, caffeine seems to actually increase DHT.³ Thereby accelerating the speed in which you lose your hair.

Caffeine and hair growth

Caffeine is also claimed to make hair grow better and faster. As proof, reference is made to a study from 2007.⁴ A laboratory study that showed that testosterone decreased the hair growth speed and that caffeine can restore this decrease. There are however some problems with this study.

First off, the study used hair that was cultivated in a lab. The cultured hair follicles were then exposed to very high concentrations of testosterone. The average testosterone value of an adult male is 9 ng/ml, whereas the study used 50 ng/ml, 500 ng/ml and 5000 ng/ml testosterone. A quantity that is 5 to 555 times higher then average.

In the study, they also state that they worked with 5 ng/ml and 10 ng/ml testosterone, but strangely enough, these results have been excluded. This comes as no surpise when we look at the results of different study. ⁵ They concluded: testosterone concentrations above 30 ng/ml reduced the growth of both cell types (hair); but lower doses had no effect.

So it seems that the results were not included in the article because they would show that 5 ng/ml and 10 ng/ml testosterone have no effect on the hair growth speed. The fact that caffeine could potentially restore the hair growth rate would no longer be relevant. Theoretically it may sound interesting, but clinically it has no relevance. After all, men have only 9 ng/ml testosterone, so there would be no delay in hair growth as a result of testosterone.

Moreover, the theoretical efficacy of caffeine also deserves more nuance. In the studies, hair that was exposed to 50 ng/ml testosterone produced a delay of 6.7%. Quantities of 0.001% and 0.005% caffeine restored the hair growth speed, but 0.15%, 0.05% and 0.01% caffeine produced an even greater decrease.

Noteworthy detail: the caffeine concentration in Alpecin caffeine shampoo is 1%.

Caffeine shampoo and caffeine absorption through the hair

Whether caffeine shampoo can be absorbed or not doesn’t actually seem to matter any more.

We nevertheless decided to review these studies as well. The previous studies proved to be unreliable and we were curious to know whether the same would be true in this case.

The main study of interest is the one published in 2007.⁶ The study showed that caffeine can be absorbed both through the skin and through the hair. When absorbed through the skin, caffeine was detectable in the blood after 20-30 minutes, but when absorbed through the hair, it took only 2 minutes. But this study, too, contains a number of problems.

Caffeine shampoo is clearly meant to be used for hair on your head, but in the study it was tested on chest hair that was cut to a length of 0.5 mm. As an argument, the authors state that the chest region was chosen for technical reasons.

We suspect that this was done because measuring caffeine intake through the hair on the head would be a lot more difficult. Namely, because there are a number of things that would drastically reduce the amount of caffeine that would be absorbed. Let us explain why.

For those who don’t know: hair is dead! The hair shaft (the visible part of your hair that protrudes above the skin) is in fact a vertical tower of dead cells bundled together. It does not absorb any substances and hence no caffeine either.

Caffeine was therefore not absorbed by the hair shaft, but by the cavity in the skin from which the hair grows - the hair follicle. Since hair on your head is thinner, so is the cafivity in the skin, thereby decrease the amount of caffeine that can pass through.

In addition, its density is greater and hair on your head is usually longer than 0.5mm. As a result, a larger amount of caffeine will remain on the hair shaft instead of reaching the hair follicle. Any caffeine that is on the hair shaft will simply be rinsed off when showering. In addition, residue from styling products will also hinder absorption.

However, the biggest limitation of the study is that the caffeine concentration was measured in the blood. Theoretically, caffeine would have to reach the hair bulb to have any effect.⁷ The fact that caffeine enters the bloodstream via the hair follicle is hardly relevant. A cup of Nespresso does the same thing.

Caffeine shampoo and unreliable study results

A large majority of the studies referred to by the manufacturer as "proof" of the effectiveness of their caffeine shampoo appear to have been financially supported by the manufacturer.⁴ ⁸ ⁹ ¹⁰ ¹¹ ¹²

This is unclear for a number of studies. We suspect that the studies from 2010, 2011, 2013 and 2018 were all conducted with financial support from the manufacturer. This is because all 4 studies were carried out by the same Italian scientists, in exactly the same way and for exactly the same company: Dr. Kurt Wolff GmbH.

The products investigated: Alpecin Caffeine shampoo, Alpecin Caffeine lotion, Plantur21 and Plantur39.¹³ ¹⁴ ¹⁵ ¹⁶ All owned by Dr. Kurt Wolff GmbH. Although the authors do not mention to have received financial support, they do thankDr.Kurt Wolff GmbH for the given product samples: "The authors thank Dr.Kurt Wolff GmbH Germany for the product samples given for the study."

We suspect that it was not just the product samples that they received. It is quite a coincidence that a couple of Italian scientists are conducting research on their own initiative into four different products for a company in Germany.

Moreover, the product samples that the researchers are talking about cost £ 2.50 in the supermarket, while the cost of carrying out research quickly adds up to £ 10,000. Why would you bear the costs of conducting research but would you not want to bear the cost for buying your own product samples?

Finally, in each of the four studies, hair loss was measured in a very peculiar way. They used a questionnaire and the "hair pull test". With the questionnaire, the efficacy of the product was determined by the participant. They were asked, for example, How effective do you think the product is? In science, such results are not done - research results that are unreliable.

The other measuring instrument, the hair-pull test, is a test in which the researcher literally pulls hairs from your head. This test is unreliable for various reasons: the researcher's pulling force varies with each pull, hair in the telogen (resting) phase is released more quickly with each pull, it is influenced by hair thickness, hair density, hair length etc.

If you really want to know whether your product works against hair loss, you have to measure its effect on DHT, cell profiling of the dermal papilla, the hair matrix, etc. The hair-pull is simply not suitable for this.

Final word

There is no evidence that caffeine shampoo stops hair loss or helps improve hair growth. The research results do not correspond to the claims made by the manufacturer and are also unreliable. Measuring instruments are not objective and the majority of studies are financially supported by the manufacturer.

It seems that studies have been produced on a continuous basis with the aim of providing positive results for a product that has not been shown to work at all. Fraud cannot be proven, but let us be honest: it definitely looks like it.