So one of the first questions I had that knew I needed to learn more about was: Where should we apply essential oils?
We'll to dig into this a little further. Let's look at the skin. Like, really look at it, as in back to your 8th grade biology picture type of look at it. Here you go, you can thank me later. On the right you see that there are three labeled skin layers: Epidermis, Dermis, and Hypodermis. Well, when essential oils are applied to the skin the first main layer they come into contact with is the Epidermis.
But even that layer has layers. The outermost layer of the Epidermis is the Stratum Corneum. This outer layer is thicker in some places (soles of the feet, palms of the hands) and thinner in others (wrists, temples). There are many essential oils that have wonderful benefits for the skin itself that you want to be absorbed by skin cells and stay there. But many other oils are effective when they are absorbed down through the layers of skin, into capillaries, and into the bloodstream where they course through the entire body. So just keep in mind, for most oils you want the oils molecules to reach your bloodstream.
Thus, the places that have blood flowing nearest to the surface of the skin can provide the best location for oils to be applied topically. I say can because there are other things that effect absorption as well, such as rate of blood circulation, temperature of skin, and possibly the number of hair follicle, pores, and sweat glands. Places on the body where the dermal (skin) layer is thinnest were mentioned before. They are the inside of the wrists, temples, inner thigh, inside of elbow, axilla, and back of neck. However, safety is always a concern, since 1) these locations have the least protective skin barrier and may therefore be much more sensitive to stimuli such as a strong essential oil. You always want to test if you are sensitive to a new oil on a small portion of skin, and if you find a sensitivity developing, such as a rash, you should rotate sites of application. And 2) You need to be think ahead and be aware of possible outcomes depending on where you apply an oil. Spreading peppermint on the temples of a child for a headache is a terrible idea as that child is likely to rub it in her eyes. And putting darn near any oil on much of the inner thighs could prove to be....somewhere between interesting and excruciating. So think first.
Other locations have their reasons as well. The back of the neck not only has blood flowing near the skin surface, but it is also very close to the brain. There are only a handful of synthetic medications that have been found to be able to go into the brain. This will be a completely separate post someday, but to summarize how absolutely amazing pure essential oils are, all you need to know is they can cross into the brain through the blood-brain barrier. Therefore the closer you can get them to the brain, the more able they are to produce their effect. The same goes for applying oils down the spinal column, which is the body's nervous system center. Oils which have been proven to have an effect on the nervous system, such as Vetiver, are most successful when placed nearest the nerves being effected.
Now to the bottom of the body. Oil application to the soles of the feet has been commonly practiced for years because it is presumed that the essential oils are absorbed through the sweat glands and pores (of which feet have many). There is some debate on this since some studies show that sweat glands and pores are not really that effective at absorbing but instead have a outward directional flow. Also, as stated before the Stratum Corneum is often thickest at the soles of the feet, many cell layers thick of tightly packed cells that essential oils would need to go through.
If you want a guide which will help you know how and where to apply doTERRA essential oils, I would suggest getting a copy of the book Modern Essentials from Amazon, Aromatools.com, or elsewhere, or looking on neweverythingessential.me which is a wonderful resource for any essential oil questions you might have.