What are essential oils and how do they differ from characteristics of the whole herb or plant?
Aromatic essential oils are hydrophobic organic materials from certain plants that are derived by steam distillation. There are only about 300 plants that produce aromatic oils which come from different parts of the plants, from tiny sacs, veins and glands. Essential oils from the bark, leaf or flower of the same plant might differ dramatically in chemical composition. You cannot assume that the herb and the essential oil will have similar properties, although sometimes they can. It is because of the low molecular weights of essential oils, that they are very volatile and can be captured during steam distillation. The chemical properties of the essential oil molecules allow them to access receptor sites in tissues, whereas the larger molecules from the whole herb cannot access the receptor sites nor bind to them, rendering them less therapeutic. There are exceptions, as is the case with poison ivy where tiny amounts of contact with the essential oil directly from a plant can show a ski
