Oils are not all the same.
Food oils, like olive oil and coconut oil, are not to be confused with essential oils. Then there are carrier oils that should not be eaten, like castor oil.
They are all oil extracts, but when a herb that does not have an abundance of oil in it is extracted; it takes a great big load of fresh herb to make a small amount of oil. This is an essential oil usually very concentrated, so it should be used sparingly and with great respect. Some herbs are endangered species and we might forever lose their beneficial properties.
These very concentrated extracts are used in aromatherapy because inhaling the essence of the plant is a very efficient and respectful way to use and preserve the powerful essence oils and beneficial properties of the plant.
When plants are dried slowly these essence oils are concentrated into the dried plant. If we don’t dry them properly the essential oils and nutrients might be destroyed.
The fresh plant has oils and other water based nutrients that can be extracted in a liquid medium like oil or alcohol or vinegar. If these plants are dried slowly these nutrients should be concentrated into the dried leaves.
The Chinese have developed drying techniques for green tea leaves where they gently steam the leaves first to prevent any fermentation, whereas with black tea the process is to let the leaves ferment. The way the fresh leaves are treated potentiates the natural properties and flavor of the leaves as they dry, and each process can develop unique flavors not found in the fresh leaves or in the leaves if they are just plain dried out. This has a lot to do with the oils and fragile aromatics in the leaves, and these are the oils that are captured for essential oils and aromatherapy.
Some plants have an abundance of oils in the seeds or fruit. Like olives or sunflower seeds for example. These abundant food oils can be used as a base, and fresh or dried cut or powdered herbs are steeped in the oils for months to draw out the fragile essential oils, nutrients, and properties into the food oil. This process happens just like we steep tea but uses a base of abundant food oil as a carrier. These food oils can be used liberally in rubs, and drops.
Any oils can go rancid if you don’t keep them in the fridge. If you need a food oil to make an herbal extraction, always open a fresh bottle (and keep the rest in the fridge to preserve it and use it in your daily cooking). This will ensure the integrity of your extract especially if you use a good source of herb to make your remedies.
As you begin working with the oils to make your herbal remedies, smell them. Your nose knows! And you will slowly begin to recognize and understand what you are working with and why things are so as you gain experience in making herbal remedies. It’s not difficult, just common sense, (which might be not so common anymore). But don’t sweat it, just have fun.
Source: What About Oils?