10.22376/ijpbs.2019.10.1.p1-12 Volume 4 Issue 1 2013 (January - March) Transdermal drug delivery system established itself as an integral part of a novel drug delivery system because of various factors like high bioavailability, absence of first pass metabolism, steady drug plasma concentration. There are many obstacles that do not allow drug to penetrate deeper into the skin. Now a day's various skin penetration enhancement techniques have been developed to limit this barrier by use of various natural penetration enhancers like essential oils. This review covers the role of essential oils in a transdermal drug delivery system as a skin permeation enhancer because of various factors like natural from its origin, promising penetration enhancement activities and mechanism of action is probably due to its increased skin vehicle partitioning by the oils. S. AGGARWAL, S. AGARWAL AND S. JALHAN Transdermal, Essential oils, Permeation Enhancers, Skin, Epidermis 857-868