Follicular Penetration of Caffeine from Topically Applied Nanoemulsion Formulations Containing Penetration Enhancers: In Vitro Human Skin Studies

In a 2018 study, researchers found that nanoemulsion formulations containing penetration enhancers oleic acid (OA) and eucalyptol (EU) significantly increased the permeation of caffeine through human skin. The study showed a 36- to 49-fold increase in caffeine permeation in skin with open and untreated hair follicles compared to control. Specifically, when follicles were open, the follicular route contributed to over 50% of caffeine permeation for both OA and EU nanoemulsions. Additionally, these nanoemulsions increased caffeine retention in open follicles by 3.4- to 4-fold. The study, which had a sample size of n = 3, concluded that nanoemulsions can effectively deliver caffeine into and through hair follicles, suggesting their potential for targeted dermatotherapy. However, larger studies are needed to confirm these findings. The research was supported by the National Health and Medical Council of Australia and approved by the University of Queensland Human Research Ethic Committee.