Dermal Absorption Rate and Administering Essential Oils Topically
Being a Massage Therapist for the past 16 years, I have seen first hand how the oils and crèames I use are absorbed into my client’s skin. I have always had a deep interest about just how much Essential Oil is actually absorbed through the skin and into the bloodstream. During my studies with Aroma Hut: I am interested more than ever about this, plus concerned about what considerations should be taken when creating an Essential Oil blend for a client and administering this blend topically. It is important to know how quickly and to what extent Essential Oils penetrate the skin and find their way into the bloodstream. It is also pertinent to understand the factors that aid or hinder dermal absorption. Dermal absorption is the transport of a chemical from the outer surface of the skin both into the skin and into the body.
The question of absorption via the skin has been fairly mysterious and full of controversy for many years. Essential oils can and do affect the skin cells, but do they get into the body via lymph or bloodstream this way? Old research showing lavender in the bloodstream within a half hour after diluted skin application did not factor out inhalation, which is the quickest and most effective way of getting an essential oil into the bloodstream. Let’s dive deeper!
First, we should revisit basic anatomy and the layers of the skin. The skin is the body’s largest organ and is essentially a water resistant barrier about 3 mm thick. The outermost layer of the skin is the epidermis, which is comprised of 4 to 5 layers (depending on the location in the body). The epidermis is broken down in layers: superficial to deep: stratum Corneum, stratum Lucidum (palms and soles only), stratum Granulosum, stratum Spinosum, and stratum Basale. As cells mature, they progress from the stratum basale, out toward the stratum corneum. By the time they reach the stratum corneum, they have become anucleated and highly keratinized. The highly keratinized nature of the stratum corneum renders it a highly effective protective barrier, especially from transepidermal water loss.
The innermost layer of the skin is called the dermis. It consists of connective tissue, nerve endings, blood vessels, lymphatic vessels, sweat glands, sebaceous glands, and hair follicles. For the purposes of transdermal absorption, the dermis provides minimal interference. The most significant barrier of transdermal absorption is the epidermis. By the time a transdermal agent has passed through the epidermis and reached the dermis, it has now gained easy access to blood vessels for systemic circulation.
For many years, biologists believed that the skin formed an impassable barrier to the outside world. We now know that this is not the case and that many substances are dermally absorbed to some degree. This knowledge has come at a great expense. For example, in the 1970s hexachlorophene was used as an antiseptic in baby soaps and talcs, causing brain damage and even death in some babies after it penetrated their skin. In fact, chemicals have been detected in human breath following dermal exposure. Nonetheless, the skin is still an important protective barrier. It limits the rate at which potential harmful substances enter the body, as well as preventing the loss of body fluids.
Since the cells of the stratum corneum are not living, they are incapable of registering a physiological response to toxic chemicals. Therefore, before an essential oil constituent can cause a toxic response in the skin or indeed anywhere else in the body, it must first cross the stratum corneum.
Considerations When Administering Essential Oils Topically
The aim of an Aromatherapist in administering essential oils is to elicit the maximum therapeutic benefits while keeping undesirable side effects to a minimum. One excellent way of administrating Essential Oils is topical applications. Essential Oils will absorb through the skin but there are other excellent benefits to consider.
Consider the route of administration
We have several choices of vehicles of administration when advising a client to use an essential oil topically.
Massage can increase dermal absorption by 34 to 158%! This may be due to the stimulating effect of massage on blood flow. In addition, when a client massages oils onto the skin, the skins overall temperature will increase due to friction and this also will increase absorption. Also, the client will inhale and thus getting the essential oil into the lungs.
Bath is another excellent way to administer essential oils. Hydration of the top layer, stratum corneum, such as occurs during a bath or shower, fosters essential oil absorption. The increase in temperature will benefit as well as inhalation.
Moisturizing lotion (an emulsion of liquid and oil) and carrier oils. When the Aromatherapist creates a lotion, butter or massage oil, not only will the Essential Oil absorb into the skin, the client will also inhale the Essential Oil as they apply the topical crème or oil, and they will receive the benefit of moisturizing the skin via the carrier oils.
Consider What Area of the Body
Medicinal products relying on skin absorption are frequently applied on areas of thinner epidermal layers, such as the axillary region. One might then assume that this would be true for essential oils, too. Some have suggested that fragrant molecules were more easily absorbed in openings in the skin, such as hair follicles and sweat glands. This gave rise to the idea that applying essential oils (often neat) to the feet, well known for their ability to sweat, was a potent way to deliver desired properties.
More recently, researchers studying absorption methods have conducted an experiment to study dermal penetration via the feet. This study was not about essential oils, but sought to investigate an urban myth claiming people could become drunk by submerging their feet in vodka. The conclusion proved that this was false and alcohol was not detected in the blood when samples were taken every 30 minutes for a total of 180 minutes. One would assume the same would hold true for essential oils. The feet’s skin layers are so much thicker than anywhere else on the body that is makes it very difficult for anything to break through.
Below is an image for absorption rates for different areas of the body.
Consider the Skin’s “health” and Age
Care must be taken if a client has irritated or injured skin. Essential oils will be able to penetrate much quicker and at a higher percentage with compromised skin. For example, in atopic dermatitis, the skin is likely to be broken so its function as a barrier to unfamiliar substances is compromised. This has obvious implications not only for the choice of an oil, but also the concentration for therapeutic effects and minimal toxicity.
Damaged skin can often benefit from using Essential Oils. This form of treatment may not be strictly ‘aromatherapy’, but it is closely allied. This is because the essential oils can have a direct pharmacological action on damaged tissues, as well as indirect beneficial effects on the mind if the aroma is perceived as pleasant.
Infant skin is much thinner than adult skin. The skin of pre-term infants is approximately 2.5 times more permeable than adult skin and before 30 weeks gestation it is 100-1000 times more permeable! Children up to three months are at increased risk of skin damage from topically applied agents. In the elderly, there is an overall thinning of the epidermis resulting in skin being more permeable. Also, recovery from skin injury is approximately three times slower in people over 80 than in those of 20 – 30 years of age.
Consider the EOs Constituents
Essential oils have a much smaller molecular weight than carrier oils and therefore pass through the skin quicker. When the molecular weight of an ingredient is under 500 Dalton (the standard measurement unit of atomic mass) then it is thought to be able to freely pass through the top layer of the skin, the stratum corneum. All essential oil constituents have molecular weights well under the 500 Dalton mark so they pass with relative ease. The thing is this: essential oil constituents, because they all have different molecular weights, will penetrate the stratum corneum at different speeds and percentages.
In 1940 a researcher called Straehli did some fascinating tests on essential oils. He found that all the oils tested appeared in his subjects’ breath following absorption through the skin. In other words, the essential oils penetrate into the skin, make it into the bloodstream, diffuse all around the body to various organs including the lungs and are then breathed out.
Further studies reveal that constituents absorb at different percentages. The “whole” essential oil does not permeate the skin at once. Terpinene and terpineol have shown no absorption through the skin, linalool (found in some 200 oils, including Rosewood, basil, clary sage, geranium) is at 2.8 to 3.6 %, geranial (ex: lemongrass, melissa, thyme, palmarosa) comes in as high as 7.3% and coumarin (found in cassia leaf, cassia bark and lavender absolute) is shown to be as high as 33%!
This study, and others that have been undertaken since then, show that essential oil constituents certainly do make it into the bloodstream – and much further than that.
Another important consideration of essential oil constituents is some also enhance dermal absorption of their own and that of other substances. Some, such as methyl salicylate, may do this in part by increasing local capillary blood flow. This could be a problem for someone who is taking prescription drugs through a dermal patch or applied to skin. Controlled dosage is important for safe and effective treatment, any enhancement from coincidental aromatherapy could have adverse effects. For example, eucalyptus oil and camphor enhanced nicotine absorption through drug patches.
- Increase in Temperature from the bath or even the friction from a massage will also increase absorption rates.
- Covered skin will absorb Essential oils quicker than that of uncovered skin. This is due to the fact that essential oils will evaporate quicker on uncovered skin and covered skin will stay warmer.
- There have even been studies done that show skin is more permeable in the evening than in the morning! Also, deeply pigmented skin has superior barrier integrity and function compared to less pigmented skin.
Safety limits have been set by Robert Tisserand, an expert in the field of essential oil safety and author of Essential Oil Safety. He states that the maximum percentage for essential oil applied topically is 5%. This is assuming the adult client has no contraindications and has healthy skin. This means dilute in a carrier oil or another vehicle to carry the essential oil. We must limit dermal dosing for essential oils that contain carcinogens (cancer causing), neurotoxic (destructive to nerve tissue), or phototoxic (skin irritation with sun exposure) constituents. For children and elderly, great caution is necessary and the dosage is much smaller than that of an adult. Essential oils are extremely potent, wonderfully therapeutic gifts from nature, but misused they can cause much harm.
I have read and heard of way too many well meaning people putting essential oils on their skin without any reservations: and even worse, advising others to do the same. I have always read from professional Aromatherapy organizations to take careful consideration when using essential oils topically. It is my passion to educate myself and others in effective yet safe essential oil use.
When administering essential oils to a client you must consider obvious things such as: is the client on medications, the age of the client, is the client pregnant, epileptic, have allergies, and/or have low or high blood pressure. In addition, there are so many other things we should consider to make our treatments as effective as possible. These are things such as: how much surface area is to be treated, what vehicle is being used (crème, oil, gel), the health of the skin, the temperature and moisture content of the skin, will the skin be covered or washed soon after administering, what constituents are in the essential oils we are suggesting and are there any contraindications and even what area of the body are we administering to. These considerations can make treatments much more effective and reduce the amount of adverse reactions.
Rebecca Park Totilo (2015) Aromatherapy Certification Program
Robert Tisserand, Rodney Young (2014) Essential Oil Safety. Edinburgh: Churchill Livingstone
Lorraine Dallmeier, Formula Botanica
US National Library of Medicine
Naturopathic Doctor News & Review: http://ndnr.com/mindbody/dermal-absorption-of-essential-oils/
Maritn Watt, Aromatic Thymes, 1995, Volume 3, Number 2, 11-13
Sylla Sheppard Hanger & Martin Watt: Cutaneous Absorption (or the lack of) of Essential Oils
Massage Today: http://www.massagetoday.com/mpacms/mt/article.php?id=14904