Essential oils are simply the distilled essences of plants. These essences are very tiny molecules that are extracted from leaves, flowers, stems and roots of flowers, herbs, shrubs, grasses and trees.
For example, if you simmer a quantity of chamomile flowers for a few minutes on the stove, you will start seeing bobs of oil forming on the surface of the water. This oil (essential oil) is the essence of the chamomile flowers. However, this description is used only as an example. The distillation/extraction processes that are used are more refined and efficient and a large quantity of the flowers will be needed to make a little oil.
The molecules of essential oils are so small that you can find as much as 40 million trillion molecules in just one drop. This very tiny size is what makes it easy for them to permeate our skin and lungs. The effect of aromatherapy is powerful because of this easy absorption.
Essential oils can be absorbed into the lungs through breathing or into the skin through massage. When they are absorbed, the molecules get into the lymphatic system and then onwards into the bloodstream Once essential oils are in the bloodstream, they start working by fighting infection, reducing inflammation, correcting imbalances and so on.