Effect of Rubbing on the Distribution of Topically Applied Drugs into the Hair Follicles

The study examined how rubbing affects the distribution of topically applied caffeine (CAF) in the skin, particularly in the stratum corneum and hair follicles, using porcine ear skin. Rubbing significantly increased CAF concentration and permeation, with more than six times higher concentrations in the viable epidermis and dermis observed shortly after application. Rubbing against the natural hair direction resulted in the highest skin permeation, likely due to changes in the hair follicle opening area. These findings suggested that rubbing enhances drug delivery through hair follicles and could inform the development of more effective topical formulations. Further research was recommended to explore different formulations and skin sites.