Role of Transepidermal and Transfollicular Routes in Percutaneous Absorption of Steroids: In Vitro Studies on Human Skin

This study confirmed that human skin appendages, such as hair follicles and sebaceous glands, played a significant role in the percutaneous absorption of steroids. In vitro experiments compared the absorption of four steroids through scar skin, which lacked these appendages, and normal skin. Results showed that absorption was significantly higher in normal skin, with progesterone and testosterone absorption being 3.1- and 2.4-fold higher, respectively, after 8 hours, and estradiol and hydrocortisone being 1.7- and 2.4-fold higher after 24 hours. The study highlighted that the absence of hair follicles and sebaceous glands in scar skin reduced steroid absorption, suggesting these appendages were crucial for the penetration of steroids and potentially other similar chemicals.