Fourier transform infrared (FTIR) (ALPHA-E, Bruker, Germany)method was used to study the physical and chemical interactionbetween the essential oils mixture and excipients. The FTIR spec-tra of the three essential oils, EC, PVP K-30 and optimized patchformulation containing the mixture of essential oils were obtained.The confirmation of IR data was cross-checked with the GC–MS(Thermo, USA) (data not shown).