Essential oils (also known as volatile oils) are the basic materials of aromatherapy. They are made from fragrant essences found in many plants. These essences are made in special plant cells, often under the surface of leaves, bark, or peel, using energy from the sun and elements from the air, soil, and water. If the plant is crushed, the essence and its unique fragrance are released.
When essences are extracted from plants in natural ways, they become essential oils. They may be distilled with steam and/or water, or mechanically pressed. Oils that are made with chemical processes are not considered true essential oils.
There are many essential oils used in aromatherapy, including those from Roman chamomile, geranium, lavender, tea tree, lemon, cedarwood, and bergamot. Each type of essential oil has a different chemical composition that affects how it smells, how it is absorbed, and how it is used by the body. Even the oils from varieties of plants within the same species may have chemical compositions different from each other. The same applies to plants that are grown or harvested in different ways or locations.