Abstract
The skin is an attractive site for direct administration of drugs due to its easy access and patient compliance. The strategy in the development of a dermal pharmaceutical and a cosmetic product lies in a selection of suitable excipients capable of delivering the drug or active pharmaceutical ingredient at the site of its action. The key moment is overcoming the least permeable skin layer stratum corneum. Chemical penetration enhancers facilitate drug diffusion and accelerate drug delivery through the Stratum corneum, possibly in combination with hydration of the skin or increasing temperature. The paper summarises basic information about the most common chemical enhancers and the studies investigating the synergistic action of suitable combinations of chemical enhancers, which may also include microemulsions.