Method
The aim of the study was to investigate the penetration of caffeine from an Alpecin shampoo into the skin and hair follicles.
Using innovative measurement techniques, it was found that caffeine not only penetrates the skin but also specifically reaches the hair follicles, where it is detectable up to 24 hours after application with just a two-minute exposure time.
Following the successful studies at the University of Jena on the effectiveness of caffeine as a stimulant for hair growth in hereditary hair loss using the hair organ culture model, it was necessary to investigate the availability of caffeine after hair washing. The preferred route of caffeine penetration was of particular importance. Previously, it was assumed that the skin, due to its protective function, acts as a barrier against the external supply of substances. The same was thought to be true for the hair follicle (Image 1). Therefore, active ingredients in a shampoo were only attributed with superficial effects.
Using two special measurement methods, researchers at the Centre for Experimental and Applied Cutaneous Physiology at the Charité in Berlin were able to demonstrate that caffeine penetrates the hair follicle after a short exposure time and can still be detected there 24 hours later.
In an initial series of experiments, participants had the caffeine-containing test shampoo applied to their scalp and massaged in for 2 minutes. The excess was then rinsed off. To make the shampoo visible under the microscope, a fluorescent marker was added beforehand.
Using innovative laser scan microscopy, it was determined after the 2-minute exposure time and the final washing process that components of the shampoo had penetrated the hair follicle (Image 2). The hair follicle showed significant fluorescence in all participants. Over the course of 24 hours, the fluorescence gradually diminished but was still clearly visible.
In two further series of experiments, the caffeine-containing shampoo was examined using a special caffeine measurement probe. First, the hair follicles were sealed with a special varnish to investigate the penetration of caffeine through the skin. After 30 minutes, caffeine was detected in the blood vessels for the first time. Even after 24 hours, the caffeine applied from the shampoo was still detectable.
In the second series of experiments, the hair follicles remained open. Here, the penetration of caffeine was significantly accelerated, and caffeine could be detected after just 5 minutes (Graphic 1). The two experiments demonstrated that caffeine preferably penetrates through the hair follicle and can therefore be rapidly available at the hair root.
The studies conducted at the university clinics in Berlin and Jena suggest that caffeine shampoo could be a suitable means of preventing premature hair loss because the caffeine from a shampoo formulation is capable of penetrating the skin and hair follicle, where it can remain available for up to 24 hours through a depot effect.
Otberg N, Teichmann A, Rasuljev U, Sinkgraven R, Sterry W, Lademann J (2007): Follicular penetration of topically applied caffeine via a shampoo formulation. Skin Pharmacol Physiol.;20(4):195-8.
