The article below includes excerpts from my book, Essential Oils for the Whole Body, released Autumn 2019, and my new book, Essential Oils from Plant to Bottle (working title) due to be released Autumn 2021 by Inner Traditions, Bear & Co.

Oral Ingestion and Neat Application of Essential oils: Dispelling the ‘myths’


Aromatherapy and the therapeutic application of essential oils, along with other remedial therapies increasingly included within an integrated holistic healthcare model, have surged into the foreground as viable methods of maintaining and managing wellness and wellbeing, and consequently, also, commercial popularity and availability.

This article aims to clarify information about the safe use and application of essential oils.

The term essential ‘oil’ is itself misleading. They are considered ‘essential’ in the sense that they carry a distinctive scent, or essence, of the plant (European Chemicals Agency 2017). The term ‘oil’ relates to their behaviour in water.  They are ‘oil-like’ in that they generally do not combine or ‘dissolve’ in water (although some ‘water-loving’ components do, hence floral waters and distillates, the majority of components do not). They are volatile (non-fixed) lipophilic hydrophobic liquids of varying viscosity comprising of very small (to varying degrees) molecules. Essential oils are mostly lighter than water, therefore, will float on the surface, or in some instances, where they are heavier and denser than water, the essential oil will sink (for example, vetivert and myrrh).  While many  molecules quickly evaporate from the skins warm, moist, surface, others penetrate with ease.

On the other hand, vegetable ‘oils’ are known as ‘fixed oils’; that is, they are non-volatile (they do not evaporate), are dense (thick), with a greasy texture, and comprise of larger molecules than those found in essential oils; they form a film on the surface of skin, and absorb into the superficial tissue layers.  They aid moisturisation of skin (that is, they slow down the rate of water loss / evaporation from the skins surface – they create a barrier), and subsequently also slow down the evaporation rate of (volatile) essential oils; thus, more essential oil molecules remain available to penetrate skin tissues and the circulatory system embedded below.  So, vegetable oils form a barrier, they dilute essential oil molecules, and facilitate wider dispersion across the epidermis, thus, protecting the skin from the irritant effect of neat concentrated essential oils.  Vegetable oils also have skin-supporting qualities of their own (anti-inflammatory, barrier repair, wound healing, anti-microbial, permeability enhancing). Please note: mineral oil and products containing other petroleum derivatives, such as vaseline, remains like an ‘oil slick’ on the skins surface, and tends to clog pores and hair follicles.

Essential oils are highly concentrated chemical derivatives extracted from various parts of plants; leaves, twigs, blossoms and flowers, fruits, seeds, bark, roots, and so on.   For example:

·       It takes 2,500 – 4,000 kg (5,511 – 8,818 pounds) of rose petals to produce 1 kg (2.2 pounds) of essential oil.

·       It takes 1.4 kg (3 pounds) of fresh lavender to produce 15ml (or approximately 300 drops) of lavender essential oil.

·       One drop of essential oil is equivalent to 15-40 cups of medicinal tea, or up to 10 teaspoons of tincture (Krumbeck 2014).  

·       One drop of peppermint essential oil is equivalent to 26 cups of peppermint tea (one to two cups of peppermint tea is usually sufficient to quell mild indigestion and stomach discomfort).  

Thus, essential oils must be used and applied in moderation and with careful consideration.  Herb teas are often sufficient remedy for digestive disorders.  Very small amounts of essential oil is required to instigate a response.


In terms of skin contact, remember, essential oils alone are not emollient and they certainly do not have an ‘oily’ texture; they are not lubricant, greasy, nor do they form a barrier. This is why essential oils should always be dispensed in an emulsifying medium (as above, and below), to soothe and protect skin, before being added to a bath (water itself is very drying to skin, which can exacerbate irritation), and they should never be added to water and consumed internally as this is virtually the same as consuming them neat (water offers no protection to the lining of the mucous membrane, stomach, or other organs of the digestive system; unless an oily or fatty medium is used, dispersants, such as alcohol, are not protective either).

NB: Essential oils prescribed for internal ingestion by a medically trained healthcare professional, pharmacist, or herbalist (and this is the only context in which oral or rectal ingestion of essential oils should be administered), are always interfused with a fixed vegetable oil and suspended in plant-based (hypromellose) or gelatin (collagen from animal skin or bones) capsules (the former being preferable), and are only administered following a thorough consultation ‘work up’; thus, dose is controlled, safe, and appropriate.

Being highly volatile, essential oil components rapidly vaporise as they bind to moisture within the skin and surrounding atmosphere. Applied neat to the skin they are thus drying and potential irritants and sensitisers, so must be dispersed in a suitable carrying medium before they are applied to the body; for example, in vegetable oil (as above), cream, lotion, ointment or gel. Certain essential oil molecules can bind to proteins within the skin and may instigate an allergic reaction (whether applied neat or in a carrier medium).

Although Tea Tree and Lavender may be applied neat to very small areas of skin as first aid remedies for insect bites, minor burns, spots etc., repeated long term application is not recommended; these oils are the exception but have equal propensity to cause skin irritation if overused.


Essential oils absolutely must not be taken internally unless prescribed and administered by a primary healthcare practitioner, pharmacist, or herbalist who is also a trained and qualified essential oil practitioner; I do not advocate oral ingestion of essential oils in any other circumstance.


Oral ingestion

There are numerous cautionary contributory factors to consider when ingesting essential oils orally. It is likely that when administered orally 100% of the essential oil ingested will be absorbed into the body’s internal system (unlike skin absorption, where the epidermis acts as a semi porous barrier), so dose is very significant. Essential oils should never be swallowed neat because they can cause severe mucous membrane irritation.

Although essential oils metabolise and are eliminated or excreted from the body quite quickly, there is increased risk of causing renal (kidney) and hepatic (liver) damage and internal irritation to other accessory organs of the digestive system. Some essential oils are oral toxins.

There is also increased risk of negative chemical interaction between the constituents of essential oils and other prescribed medication that may be being taken at the same time, which might potentiate or exacerbate their action. For example, sweet birch or wintergreen essential oil should never be administered internally if a person is also taking Warfarin, as these essential oils dangerously increase the anti-coagulant and blood thinning potential of Warfarin. In other examples, Tisserand and Young (2014 p 58) warn of possible incompatibility between oral ingestion of chamomile German (blue), chaste tree, cypress (blue), jasmine sambac absolute and sandalwood (W. Australian) essential oils (Latin names not given) and tricyclic antidepressants, such as imipramine and amitriptyline, or opiates such as codeine, because these essential oils can potentiate the action of these drugs and other CYP1A2, CYP2C9, CYP2D6, CYP3A4 substrates (inhalation and topical dermal application of balsam poplar, chamomile blue, sage and yarrow may also potentiate the action of CYP2D6 substrate drugs).


Skin reaction

There are three main forms of skin reaction to essential oils:

  • Irritation
  • Sensitisation
  • Photo-toxicity



 Irritation may manifest as localised inflammation, affecting the skin or mucous membrane. The respiratory tract is particularly susceptible to inflammatory and non-inflammatory irritation from essential oils (experienced as drying, burning, stinging, tingling, tickling). Some essential oils are useful for conditions affecting the respiratory system (sore throats, bronchitis etc.) but should be applied in low doses for a short duration when they are applied as inhalants, to avoid respiratory irritation. Phenols and aromatic aldehydes tend to be the most irritant essential oil compounds.   For example, eugenol (basil, cinnamon bark, clove), thymol (basil, thyme), carvacrol (thyme, oregano, savoury), cinnamic aldehyde (cinnamon leaf).



Sensitisation is not the same as ‘sensitive skin’.   Sensitisation is a contact hypersensitive or allergic reaction and/or severe irritation that involves the immune system (T-lymphocytes and macrophages). T-lymphocyte cells become sensitised through an adaptive, exaggerated or inappropriate immune response; once sensitised, even a small amount of the potential antagonist substance can cause a reaction. Sensitisation is not dose dependent and is difficult to predict. Also, a sensitised reaction may be delayed, symptoms manifesting sometime after application.

The saturation point of chemical exposure can be reached through contact with products other than essential oils, such as cosmetics, perfumes, household cleaning materials etc.; there can also be a potential insidious cumulative effect especially where the same products are used repeatedly.

Symptoms of sensitisation are various and may include skin irritation, rashes, headaches, migraine, anxiety, heart palpitations, feelings of unease, shortness of breath and dry mouth.

All essential oils are potential sensitisers and therefore should be applied in moderation, with regular breaks or abstinence from use (two to three weeks use followed by a week’s non-use), and periodical rotation of the essential oils applied (substituting one for another appropriate oil), especially if using regularly over a long period of time. Essential oils should never be applied ‘neat’ to skin



Toxicity refers to the strength of a poison and the degree to which a substance can damage or destroy an organism, whether the whole organism, such as a plant or animal, or a substructure of the organism, such as a cell or organ, for example, liver (hepatotoxicity), kidney (nephrotoxicity).   Damage may be reversible or irreversible, depending on the level of biological disruption and whether the regeneration capacity of the affected cells has been compromised.

Toxicity is dose dependent and is influenced by factors such as the route of administration (skin absorption, ingestion, inhalation), length of time of exposure, frequency of exposure, the genetic makeup of the individual and their general state of health. Localised toxicity usually affects the organs of elimination (stomach, liver, kidneys, intestines, lungs and skin). A toxic reaction instigated by essential oil molecules can manifest at the point of topical application or systemically.

Some essential oil molecules, which may otherwise be non-toxic, can bind with compounds contained in medication (most of which are toxic substances) or certain foods, or with certain enzymes and be metabolised into a toxic substance or relocate to an area within the body where they may cause damage. Camphor and methyl salicylate compounds, and clove, cinnamon and eucalyptus essential oils are most frequently cited as causes of systemic toxicity in humans. Most reported essential oil poisoning incidents involve children under six years old who accidentally ingest the oils.

Chemical components with in essential oils can become toxic when they oxidise and degrade. Old essential oils are more likely to be toxic than freshly extracted, appropriately stored, essential oils (especially citrus and pine oils). Essential oils containing phenols, fragrant aldehydes, and oxidised terpenes are the main culprits for causing dermal toxicity and irritation.



This is an excessive reaction to sunlight (or UV light, including UV light emissions from sun-tanning lamps) induced by certain chemicals present within the superficial layers of the skin. Phototoxic substances (such as furanocoumarins found in a few essential oils, for example, bergamot and angelica root) absorb UV light, which in turn causes the production of abnormally dark pigmentation (brown patches), that may last for years, and reddening and burning of the surrounding skin, which is often slow to heal. A phototoxic reaction only occurs if the sensitising agent is present. Avoid phototoxic essential oils on skin exposed to sunlight or UV light and sun-tanning lamps.


In conclusion

When applied sensibly and in moderation, essential oils are extremely beneficial. However, they can also cause harm, especially when applied inappropriately.  Always check the therapeutic effects and safety information of an essential oil before applying it, especially if you are taking medication (prescribed or ‘over the counter’), or are receiving medical treatment, or have a compromised immune system, or have allergies or sensitivities to products, metals, foods and other substances.  Do not apply essential oils to other people unless you are qualified to do so.  Ensure the authenticity and age of your essential oil before applying (once opened, essentials have a 12 month shelf life, citrus oils, 6 months – unopened and stored correctly, then 2 years). Store in a cool, dark place away from sunlight (such as a fridge – although some essential oil solidify, rose for example, they return to a liquid state at room temperature). Always ensure lids are replaced immediately after use. Wash any residue essential oil from your fingers to avoid contact with your eyes or other sensitive areas of your body.


Example of an extreme adverse reaction:



  • Clarke, S. (2002) Essential Chemistry for Safe Aromatherapy: Churchill Livingstone, London
  • Godfrey, H. D. (2018) Essential Oils for Mindfulness and Meditation: Inner Traditions Bear & Company, Rochester USA
  • Godfrey, H. D. (2019) Essential Oils for the Whole Body (publication pending): Inner Traditions Bear & Company, Rochester USA
  • Tisserand, R.; Young, R. (2014) Essential Oil Safety (2ndEd): Churchill Livingstone, London
  • Tisserand, R. (2018) In defence of science, and of safety precautions:


For more details and information about the safe application of essential oils, and much much more, please refer to:

Essential Oils for the whole Body














Essential Oils for Mindfulness and Meditation