Effect of Rubbing Application on the Skin Permeation of Active Ingredients from Lotion and Cream

The study investigated the effect of rubbing application on the skin permeation of caffeine (CAF) and rhododendrol (RD) from lotion and cream. It was found that rubbing significantly increased the skin permeation of CAF, especially when applied against the direction of hair growth, while no enhancement was observed for RD. The increased permeation of CAF may be due to changes in hair follicle orifice size caused by rubbing and skin stretching, whereas RD's high distribution in the stratum corneum might explain the lack of enhancement. These findings could aid in predicting the safety and effectiveness of topical formulations.