Pharmacokinetics and Routes of Administration

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Essential Oils can be absorbed into the body by many of the same routes as conventional medications: they can be swallowed orally, inhaled through the nose and mouth, or absorbed through the skin and mucous membranes. Each route has its own risks and benefits.


EOs are lipid soluble, which means that most of the molecules are readily absorbed through the dermal layers of the skin into the blood stream.

How quickly this happens depends on the weight, polarity and optical properties of each individual molecule. Skin permeability also plays a role. The most permeable areas are thought to be the palms, soles of the feet, forehead, scalp and axillae (9). Although this might suggest that lack of hair increases permeability, hair shafts actually facilitate transfer of EOs to deeper dermal layers.

Damage from sun exposure, abrasions and rashes can also increase skin permeability. Heat or friction from massage can stimulate blood vessel dilatation, additionally aiding absorption. However, since skin contact with many undiluted essential oils can result in dermal irritation, they are usually combined with carrier oils, such as almond or grapeseed oil, which acts to dilute the EO and slow the absorption rate. Mucous membranes found in the eyes, nose and mouth are thin, thus highly permeable, and contact with even trace amounts of undiluted EOs can cause irritation and pain.


EOs can be taken orally. Popular methods include instillation into gelatin capsules, mixing with an emulsifier and water, or combining with honey. Oral doses can be particularly effective at treating infections and gastrointestinal complaints such as irritable bowel syndrome (IBS) or chemotherapy induced nausea. In truth, most people ingest small amounts of essential oils with regularity. Peppermint and Spearmint EOs in particular, are commonly used to flavor candy, gum, medication, toothpaste and mouthwash. While there are trained and licensed specialists in other countries who are skilled and knowledgeable in dispensing oral EOs safely, this is not a widely accepted method of use in the US.


The molecules in EOs are rapidly transported when inhaled, to both the blood stream and the central nervous system.

Via the nasal route, the EO vapor enters the nostrils, where it contacts the olfactory receptors. These receptors are composed of cilia, surrounded by fluid, which is secreted by special olfactory glands. The EOs are dissolved in this fluid, then travel along the olfactory tract to the olfactory bulb in the cerebrum. Due to the close proximity of the nostrils to the base of the brain (just above the bridge of the nose), an EO can elicit central physiological effects quite rapidly.

Essential oil vapor accesses the pulmonary system by entering the lungs via the nasopharynx and trachea. Traveling through the bronchus and the bronchioles, the EO vapor ultimately encounters the alveoli, millions of tiny grape-like clusters with thin walls, which permit rapid diffusion into surrounding capillaries. From there, EOs are transported through the circulatory system to appropriate receptor sites throughout the body.

For hospitalized patients, particularly in the perioperative environment, inhalation is by far the safest, fastest, and in some cases the most effective method of EO delivery.

Many ways of dispersing essential oil vapor into the air exists. From a few drops placed on a cotton ball, to whole-room electric heated diffusers, getting essential oils to vaporize is truly as simple as removing the lid of the bottle.

For use with patients, however, their level of consciousness and physical impairments often require safety measures that exclude the simpler methods. When treating a symptom such as nausea, a personal passive inhalation device is more appropriate than using a whole room diffuser. The lowest effective ambient concentration to achieve relief is the safest and best practice to employ in a clinical setting.

Back to: Therapeutic Inhaled Essential Oils (TIEO) for the Clinical Setting


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