What you need to know about your skin-part 1
“By nurturing skin using natural products, we provide optimal support for it to perform its vital functions such as protection, sensory perception and thermoregulation, as well as improving its aesthetic qualities. ”
Did you know that the skin is the most voluminous organ in the human body, comprising as much as 15% of the total adult body weight?
In this two part overview we will explore a a few facts about this incredible organ and how aromatic therapy can help support and maintain healthy skin
Part 1 is a brief overview of the structure and basic functions of the skin and how compounds such as essential oils are absorbed.
Part 2 will discuss the issues of skin integrity and the ways in which essential oils can help support the its capacity to defend itself and heal
What is the skin?
Skin is the main barrier between the internal body and the external world, protecting the body against biological, chemical, mechanical, and ultraviolet threats and contaminations.
Deeply sensitive and resilient, the skin is a super-organ, maintaining systemic homeostasis responsible for:
thermoregulation
preventing excess water loss
absorption and elimination
vitamin D synthesis
mediating the interrelationships between the immune, neurologic, and endocrine systems.
Human skin is made up of three layers
the epidermis
The epidermis is the outermost layer, the skin barrier, and protects the body from potentially damaging environmental factors. The epidermis is characterised by a constellation of tough cells known as keratinocytes. These cells synthesise the protective protein keratin, a fibrous, alpha-helical filament that renders the epidermis strong and flexible and waterproofs the skin's surface.
the dermis
It is the thickest layer, made of dense connective tissue with blood and lymph vessels, nerves, hair follicles, and glands. The thick layer of dense connective tissue is primarily composed of threadlike fibres of structural protein collagen.
Collagen production in the dermis gives the skin its strength and flexibility.
the hypodermis
The hypodermis thus regulates body temperature. It is mainly made up of fatty and connective tissues that house larger blood vessels and nerves, and help insulate the body from heat and cold.
Skin is the body’s barrier
As mentioned above, the epidermis acts as a barrier against external contaminants.
The skin barrier has a critical function in maintaining skin integrity through :
skin permeability
prevention of water loss
antimicrobial protection
protection against UV radiation damage.
Elements of the skin barrier are
The stratum corneum is made up of cells called corneocytes that act as bricks.
The lipid matrix is a mortar-like substance, comprised of fats such as ceramides, cholesterol, and fatty acids. This layer also contains a protein called filaggrin, which helps make natural moisturising factors for the skin.
The tight junctions connect neighbouring cells and help prevent the passage of unwanted substances between them.
The integrity of these elements will affect the skin's permeability and the absorption of EO constituents.
“Transdermal permeation of essential oil molecules is complex, involving many possible steps from initial application to their arrival in the systemic circulation.
”
Penetration and absorption
Essential oils are composed of tiny chemical constituents that can easily penetrate the skin and be absorbed. When applied to the skin, EO constituents pass from the stratum corneum into the lower layers of the epidermis, are absorbed into the lymphatic system via the tissue fluids, and from there eventually reach the bloodstream.
Essential oil constituents have different densities and are generally lipophilic (fat-loving), although some are more hydrophilic (water-loving). It is these oil- or water-friendly qualities that will determine how easily or quickly they penetrate the skin barrier and which path they tend to take through the stratum corneum
Photo courtesy of Building4Health
Three routes of absorption:
Intracellular penetration through the corneocytes. More water-friendly constituents will prefer to traverse the epidermis via the intracellular route
Passage through intercellular spaces. More fat-friendly constituents will tend to cross the stratum corneum via the intercellular passage
The transappendageal route, via the sweat glands and along hair follicles with their associated sebaceous glands. This route bypasses penetration into the stratum corneum.
The aromatic therapist’s decision on the best method for applying an essential oil treatment will depend on the client's purpose and the required action.
For instance, in general skincare treatments, absorption into the bloodstream is neither necessary nor desirable, as we want to keep EO constituents' actions to benefit the epidermis/dermis layers for as long as possible.
In treatments for joint or muscle pain and inflammation, some absorption of essential oil constituents into the systemic circulation is required. While treatments for joint or muscle tissues aim to be locally effective, it can be beneficial for constituents with pain-relieving properties to enter the bloodstream and reach the brain, where they exert analgesic and antinociceptive effects.
Factors to be considered
Method of Application
Applying EOs to the part of the body with the thinnest skin, such as the inner wrists and ankles, behind the knees and inside the elbow, on the neck and temples, will increase transdermal absorption to some degree.
Application to a larger area of skin, as in a full-body massage, can result in the highest absorption. Additionally, mechanical friction from massage improves absorption by increasing blood flow, temperature and altering the structure of the stratum corneum, making the skin even more permeable.
Environmental factors
UV exposure, air pollution, and tobacco smoke, when combined with genetic factors, can impair the skin's barrier function, leading to increased water loss and structural changes in the stratum corneum. The consequence is increased skin permeability, which makes already-damaged skin even more vulnerable to irritants.
Dose and dilution
Safe and appropriate doses and dilutions, usually in vegetable oils, also influence the absorption rate. Although undiluted EOs may result in higher concentrations of constituents in the skin than diluted EOs, the increased risk of adverse effects, such as irritation and allergies, makes such use highly undesirable. Additionally, research has shown that higher concentrations actually lead to lower absorption. However, there are Eos, such as lemon, that are known to act as skin penetration enhancers. I will discuss the use and mechanism of action of penetration enhancers in Part 2.
The base
The base, or vehicle, in which EOs are diluted will also influence the rate of absorption.
Vegetable oils are the most common bases for dermal conditions and skincare, but studies comparing the absorption rates of EO constituents in a hydrogel (water-based gel), emulsion, or oil show that constituents from the hydrogel base penetrate the skin most efficiently.
The greater absorption from a hydrogel can be explained by the tiny lipophilic (oil-loving) EO constituents, which will naturally seek to migrate into the more lipophilic medium of the stratum corneum.
However, depending on the treatment's purpose, this does not necessarily mean a gel is the most appropriate vehicle. For example, Tamanu oil has anti-inflammatory and nervine actions, which are particularly helpful for sciatica.
As already mentioned, a vegetable oil base will be more appropriate for skin care and healing, where you want the essential oils to act on the surface, whereas a hydrogel will be appropriate for muscular and joint pain and wound healing, where you want the Eos to penetrate into the tissues.
Disturbed skin barrier function
A disturbed barrier function may allow potential toxins and allergens to penetrate the skin more easily.
The causes may be due to
ageing
UV rays
sleep
allergies
hormonal changes
genetic influences
excessive smoking
alcohol consumption
unhealthy life-style habits and nutrition
psychological stress
seasonal or climate changes
A disturbed barrier function is often associated with excessively dry skin and is at the origin of various skin conditions such as eczema and psoriasis.
To summarise
All too often, though, we take our skin for granted and overlook the need to look after and nurture this precious physical boundary so that it continues to offer us optimal protection from the adverse elements of our environment and lifestyle choices.
Caring for our skin is as important to our wellbeing as fixing a leaky roof over our heads. Neglect of our skin allows toxins to seep into our bodies, causing disarray to our physical and emotional wellbeing.
References
Bensouilah, Janetta,Buck, Philippa. Aromadermatology: Aromatherapy in the Treatment and Care of Common Skin Conditions (p. 206). CRC Press
Jade Shutes, study notes from my ongoing studies at School of Aromatic Studies
Cal, K. (2006). Skin penetration of terpenes from essential oils and topical vehicles. Planta Medica, 72, 311–316. http://doi.org/10.1055/s-2005-916230
Harding, C. R. (2004). The stratum corneum: structure and function in health and disease. Dermatologic Therapy, 17, 6–15. https://www.ncbi.nlm.nih.gov/pubmed/14728694
Mojumdar, E. H., Gooris, G. S., Groen, D. et al (2016). Stratum corneum lipid matrix: Location of acyl ceramide and cholesterol in the unit cell of the long periodicity phase. Biochimica et Biophysica Acta, 1858, 1926–1934. http://doi.org/10.1016/j.bbamem.2016.05.006
Tagami, H. (2008). Location-related differences in structure and function of the stratum corneum with special emphasis on those of the facial skin. International Journal of Cosmetic Science, 30, 413–434. http://doi.org/10.1111/j.1468-2494.2008.00459.x
Tisserand, R. Young, R. (2014). Essential oil safety, 2nd edition. Churchill Livingstone, Edinburgh http://roberttisserand.com/essential-oil-safety-book-second-edition/
Wertz, P. W. (2018). Lipids and the permeability and antimicrobial barriers of the Skin. Journal of Lipids, 2018. http://doi.org/10.1155/2018/5954034
