Is there any science to the art of aromatherapy?

A lot of people are using essential oils these days, throwing a few drops in the bath, adding some to a vegetable oil, diffusing in their home now and then, but do you know how the body and brain absorbs them? Let’s take a look at the pharmacokinetics; I promise to keep this as brief and relevant as possible.

For all those out there with some healthy skepticism, hopefully this might go someway to reassuring you, that there is science to the art of aromatherapy.

The skin

Our skin is one of the most popular routes of administration for oils. They can be applied with a massage, or locally on isolated skin problems. The oils are effective at penetrating superficial skin problems. However, topical absorption can also be used to treat your body’s systems and organs too.

It is a little trickier for the oils to be absorbed through all the upper layers of the skin, but still possible. The small surface area of eccrine and apocrine glands, hair follicles and their sebaceous glands, are one of the major routes of absorption for the oils through the skin.

The most permeable areas are head, soles, palms, armpits, mucus membranes and genitals. Hence you often hear people say, apply the oil to your feet at night! Once the molecules have been absorbed, the capillary blood circulation then carries them away.

Studies have shown that absorption is improved with increased blood flow, meaning that potentially being massaged with oils will help to increase systematic absorption.


One of the most ancient methods of absorbing sacred incenses and burning herbs was through inhalation. The molecules are absorbed by the lungs and transported around the body via the blood circulation.

The body tissue with most blood flow and lipid rich tissues will be the most exposed to the action of the oil, whilst the tissue with the least blood flow, will have less chance to benefit from the action of the oils. So for example, easier to reach are endocrine glans, heart, lungs and brain, but harder to reach, are things like bones, teeth and ligaments.

Olfactory system

Olfaction is the act of smelling. The Olfactory system and its effects have been poorly understood for a long time. Your olfactory system can differentiate literally millions of different smells, even similar chemical components can have quite different odours.

The act of smelling begins in the nasal cavity, where the mucosa dissolves the odorous molecules, this activates olfactory receptors and the olfactory bulb is where messages are processed. Next they move on to different pathways in the brain, the thalamus and hypothalamic region. The pathways of the olfactory system converge in an important area of the brain, the limbic system. 

The thalamus is the sensory processing part, which enables us to differentiate and identify the correct odour. The hypothalamic region, which is part of our limbic system, regulates the autonomic nervous system and links our nervous system with the endocrine system (hormones). The autonomic nervous system controls things like respiration, digestion and blood pressure.

The odorous molecules of essential oils are able to go to the brain via the olfactory system. The essential oil molecules like the lipid rich tissue of the brain which enables them to pass the blood brain barrier, this barrier normally protects us from toxicity.

OK, so what exactly does all this mean when you use aromatherapy?

The very act of smelling the oils means that their chemical constituents are processed in the brain and can then affect our autonomic nervous system, similarly to that of a pharmaceutical drug like a tranquillizer for example.


Each essential oil has a unique combination of chemical constituents, which interacts with the body’s organs and systems.

They enter our body’s system through the skin, or inhalation to the lungs and subsequently are distributed via the blood system to organs. Additionally, the odours are processed through the olfactory system and reach the brain affecting not only our systems, but also our emotional wellbeing.

This all sounds pretty impressive doesn’t it? The problem lies with their reliability; do they have the same effect each time? Are the clinical trials meaningful? From a clinical perspective the oils are unpredictable, they contain hundreds of chemical constituents that change and interact differently person-to-person. Therein lies their beauty and power at best, but at worst making them hard to define and unreliable. 

I leave this information with you, food for thought isn’t it? In a future post, I will take it a step further and give examples of analysis from clinical trials, so we can debate, do the oils really work?

 A final note

There are of course other ways to absorb the oils, internally or orally. As Aromatherapists we are not qualified to advise on oral absorption. We may prescribe internal routes via mouthwashes and vaginal douches for example only. Please be cautious when anyone advises internal routes, they should be a medical doctor, qualified herbalist, or naturopathic doctor. I have also not covered how the oils are excreted in the body, which is a similar pharmacological process to medical drugs.