Abstract: Theory of Drug Properties (TDP) is the core of the theory of traditional Chinese medicine(TCM). As major active substance of TCM， the application of essential oils （EOs) as penetration enhancers (PE) should be guided by TDP. In the present paper， based on the theory of Yin and Yang， as well as the understanding of drug properties of EOs， EOs are divided into three categories， such as "natures and flavours belong to Yang"， "natures and flavours belong to Yin" and "natures and flavours belong to Yin and Yang". Moreover， according to the literature analysis， it is found that the number of the papers of EOs with hot or warm natures and Pungent flavour in the treatment of cold syndrome is significantly more than those of the other two categories. Based on the knowledge of pungent flavour in TDP， such as "open skin slit" and "the pungent flaver related with four natures"， the application of EOs with "natures and flavours belong to Yang" as PE in transdermal formulations for cold syndrome is proposed， which is expected to make full use of the "Synergistic Effects" of EOs.