Without a shadow of a doubt, the most popular recommendation for the topical application of essentials oils on the Internet and social media is the bottom of the feet. Would you be surprised if I told you that the feet are not one of the “best” places on your body for absorption? Let’s take a closer look at why that is.
The Integumentary System
The Integumentary system, also known as the skin, has three main layers: the epidermis, dermis and subcutaneous (fat) layer. Our skin is the largest system of the body and acts as a barrier from many things in the outside world such as microorganisms, toxic agents/chemicals and guards against dehydration. The outermost layer of the epidermis, the stratum corneum, serves as our body’s primary defense.
The stratum corneum is an impressive structure of defense made up of 18-20 or more layers of corneocytes, depending on the anatomical location on the body. Corneodesmosomes are what holds the corneocytes together. There is a mortar type layering stacked between the corneocytes, comprised of ceramides, cholesterol and free fatty acids (1). Within and around these structures are lipids, which are compromised of a mixture of naturally occurring molecules, including various types of fats. This is important in the topical application of essential oils, more on this later.
Not everything we put onto our skin is fully absorbed into our bodies. If this were the case, we would swell something awful while soaking in the bathtub. However, when we do sit in the bathtub for an extended period of time, we get quite the wrinkled look on our fingers and toes. So this tells us that a small amount of absorption does take place (2).
In order to understand our skins ability to absorb essential oils topically, we need to understand the types of glands of the body, how they work, and other various factors of our skin.
We have two types of sweat glands: eccrine and apocrine. The eccrine gland is the common type of sweat gland found all over the body, but is found primarily on the palms of the hands, soles of the feet and forehead (eccrine glands differ from the apocrine sweat gland found in the armpit).
Why do we sweat? The purpose of the sweat gland is the body’s way of cooling itself. This is called thermoregulation and acts much like a furnace. You set a temperature on the thermostat in your home. When the temperature falls below that set degree, the furnace kicks on to maintain the desired temperature. The body needs to maintain a core temperature as well, and thermoregulation makes this happen. Explained at an elementary level, when you get hot and your body temperature rises, you sweat in an effort to cool your body down. When you are cold, your body sweats much less, and you shiver as a means of bringing your temperature back up. Hair on your arms and legs also stands on end, causing the glands to close so that your body can efficiently trap in heat, and is the cause of what we know as goose bumps (3).
When a sweat gland is stimulated, the cells secrete a solution of primarily water, with concentrations of sodium, chloride, and a small amount of potassium; also known as sweat.
There are two very important points to review in regards to this information. The first is the direction of flow so to speak of the eccrine sweat gland, and that is “out” of the body (excreting). This tells us that absorption of essential oils on the bottom of the feet, which in its nature is going “inward”, happens in minute amounts compared to other areas.
The second point, which is rooted in chemistry, is a term called “like dissolves like.” This tells us that a solvent will dissolve substances that have a similar structure (4). Essential oils are considered lipophilic (fat loving). You have undoubtedly heard that essential oils should be diluted in a fatty based carrier oil before applying to your skin. Diluting in this way not only protects you from potential skin irritation, it keeps the essential oil from quickly evaporating and allows them to slowly absorb into the skin.
We now know that an eccrine gland secretes water and is therefore an aqueous environment. The absorption of essential oils in a lipid based carrier oil happens in very minute amounts through a sweat gland.
At the base of our hair follicles are sebaceous glands. These sebaceous glands produce an oily secretion to help condition the hair and surrounding skin. This makes hair follicles lipophilic due to its oily secretion. Recent studies have shown that hair follicles can act as conduits into our skin. It has been shown that chemicals are absorbed into the skin much more quickly through hair follicles than through adjacent sections of skin that don’t have hair follicles (5).
This shows us that absorption of essential oils in a lipid-based carrier oil can happen relatively easily due to the fact that hair follicles absorb in an “inward direction”.
Other Skin/Essential Oil Considerations
There are a few other considerations where essential oils and the skin are concerned:
*Age of skin. Babies and small children have immature skin, and elderly have thin skin. This increases the permeability of essential oils. Topical application needs to be performed in lower dilution percentages and with extra precautions.
*At best, 10% of a leave on essential oil blend will absorb when properly diluted (wash off products will be less than this)(6).
*Essential oil constituents vary in their molecular size. Smaller molecules more easily penetrate the skin, whereas large ones may penetrate very little, if at all.
The Best Bet For Your Feet
The excipient used can affect the rate of absorption of essential oil blends. For example, gels increase the rate of absorption, and fatty based carrier oils slow down the rate of absorption. There are benefits to both!
Therefore, my recommendation for application of essential oils to the bottom of the feet would be in an aloe vera gel (different from aloe vera leaf extract), rather that a lipid-based carrier oil. Aloe vera gel is water based and will increase the rate and efficiency of absorption (aloe vera gel is a penetration enhancer) (7). Plant Therapy sells a variety of Aloe Vera Jellies, perfect for this type of application.
Common Misconceptions About The Feet
*Reflexology proves that essential oils absorb through the bottoms of the feet. -Reflexology is typically performed on dry feet, no oil. The preface of reflexology is to apply various pressure techniques to certain reflex points on the feet that communicate to other areas of the body. It is NOT the essential oils on the feet that are doing the communicating (8).
*The pores of the feet are large, increasing essential oil absorption. -The absorption that does happen through the bottom of the feet are not influenced by the size of the pores, rather the chemistry of the excipient/substance being used.
*The bottoms of the feet are the safest place for babies. – It is important to know that using essential oils in any form for small babies under three months of age is not typically recommended. Few oils should be used topically between three months and two years of age. Any parent knows that babies/toddlers love to play with their feet and bring them close to their face, so any essential oil applied to the feet will be inhaled. This is likely how “absorption” is occurring in these instances, via inhalation/the lungs. I recommend gentle diffusion to obtain the same effect while removing the risk of irritating baby’s skin.
Upon closer examination, we can now see that essential oils can be applied to the bottom of the feet, but we must consider the excipient/substance being used. The most effective places for topical application of essential oils in a fatty based carrier oil are:
*Where you have the most hair follicles
*The abdomen (9)
*The inside of the arm (10)
*And lastly, closest to the nose for maximum inhalation
Always remember that the quickest way to the blood stream will always be via inhalation. Providing you with trusted information so you can make the best decisions for you and your family, safely.
(1) Menon, G., Cleary, G., Lane, M. (2012) International Journal of Pharmaceutics. The structure and function of the stratum corneum. 435: 3–9
(2) Why do fingers wrinkle in the bath. Retrieved from https://www.scientificamerican.com/article/why-do-fingers-wrinkle-in/
(3) Homeostasis. Retrieved from http://biologymad.com/resources/A2%20Homeostasis.pdf
(4) Understanding “Like dissolves like”. Retrieved from https://www.youtube.com/watch?v=OIhWWpvKOTM
(5) Hair biology, hair follicle function. Retrieved from http://www.hairbiology.com/hair-follicle/hair-follicle-function.shtml
(6) (9) (10) Tisserand, R. Complete skin series. part 2, transdermal absorption. http://tisserandinstitute.org/
(7) Hamman, J. (2008) Composition and applications of aloe vera leaf gel. Molecules 2008, 13(8), 1599-1616://www.mdpi.com/1420-3049/13/8/1599/htm
(8) Kreydin, A. (2014) Essential oils and the feet. Retrieved from http://www.amykreydin.com/essential-oils-and-the-feet/
Leslie Moldenauer, CHNC, HHP, Certified Aromatherapist, has been studying natural living and holistic wellness for over 10 years. Leslie is a trusted resource that covers essential oil safety and encompasses all that natural living has to offer. She is passionate about providing education and tools to help others make decisions regarding safety above all things when utilizing aromatherapy in the home.