The composition (including both main components and those in low amount but with significant biological/therapeutic effects) of the essential oils varies depending on the geographical position, the plant’s origin and species, harvest time, distillation/extraction procedure, etc. [17]. Additionally, the composition of the essential oils and consequently their biological/therapeutic activities depend on the combination and ratio of their numerous different components. Gas chromatography coupled with mass spectrometry (GC-MSD) and flame ionization (GC-FID) detectors was used to determine the quality and quantity of chemical compounds in the essential oils.