Several chemicals are known to interact with the skin and disrupt the highly ordered lipid bilayer structure in the stratum corneum. This observation led to the study of chemical agents to enhance transport across skin. More than 300 chemicals have been studied for their ability to increase skin permeability (Karande et al. 2004) . Chemical permeation enhancers are relatively inexpensive and easy to formulate, they offer flexibility in their design, are simple in application and allow the freedom of self-administration to the patient. Chemical enhancers comprise a wide variety of different chemical functional groups and facilitate drug transport across the skin by a variety of complex mechanisms. They can directly exert their effect on skin structure by acting on intercellular lipids or corneocytes. Chemical enhancers can extract lipids from the skin thereby creating diffusion pathways for transdermal permeation. Alternatively, they can partition themselves into the lipid bilayers thereby disrupting the highly ordered lipid lamellae and causing their fluidization. Chemical enhancers can also significantly increase skin transport of a drug by enhancing its thermodynamic activity in the formulation (Karande et al. 2005) .