The role of hair follicles in the percutaneous absorption of caffeine

The study from 16 years ago showed that hair follicles play a significant role in the percutaneous absorption of caffeine. In the experiment with six healthy male volunteers, caffeine was absorbed more quickly and reached higher blood concentrations when hair follicles were open compared to when they were blocked. With open follicles, caffeine appeared in the blood at 3.75 ng/ml within 5 minutes, while blocked follicles delayed detection until 20 minutes with a concentration of 2.45 ng/ml. The peak concentration was 11.75 ng/ml at 1 hour post-application with open follicles. These findings suggest that hair follicles are important pathways for the rapid delivery of hydrophilic substances through the skin, which is relevant for the development of topical treatments and products, and could be especially significant for conditions like androgenetic alopecia or acne. However, the study's scope was limited to caffeine, indicating a need for further research on other substances.