Essential oils are useful for smooth skin and massage as well as aromatherapy. For those unfamiliar with what it is, please refer to this Article about essential oils. It is made primarily from plants, apparently, but the oil is extracted, distilled or expelled using steam or vapors. For the purpose of this question, let's only consider the ones that come from plants.
Does this process alter the nature of the plant in any way as it seems you would be making the bracha on an "extract" or plant condensation from the steam process?
