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Essential Oils 

What are Essential Oils?

Essential oils are extracted from aromatic plants, including flowers, leaves, roots, resins, seeds and fruit, with each essential oil having its own unique properties. Essential oils are aromatic, volatile substances extracted from a single botanical source, by distillation or expression (citrus fruit peel only). When these methods cannot be used successfully e.g. jasmine flowers, solvent extraction is used resulting in ‘absolutes’. Explore different methods of extracting essential oils by clicking here.

Essential oils are secreted from special glands, ducts or cells in one or several parts of the aromatic plants and from the sap and tissues of certain trees. These natural essences are present in the roots, stems, barks, berries, leaves and/or flowers in varying quantities, and in certain botanical families they are more abundant than in others. The plant uses these essences for many of the same things that we do, such as wound healing, fighting infection and repelling insects. You may therefore often hear them being referred to as the spirit and heart of the plant.

Some essential oils may present safety challenges such as skin and mucous membrane irritation or phototoxicity. Some interact with drugs (e.g. anticoagulants) or might not be suitable for those suffering from epilepsy or pregnant/breastfeeding women or babies, see safety page for more details.  

Essential oils are used synergistically in aromatherapy practice where their distinctive therapeutic properties can help bring about a relaxing and calming effect for those suffering with mental health problems, dementia and those receiving palliative care for example. As a result, it is also used in a variety of settings, including hospitals and hospices. 

Composition of Essential Oils

Essential oils are powerful substances and have a very complex chemical composition which may vary from batch to batch, depending on the growing conditions. Whilst essential oils are stored in the plant, they are constantly changing their chemical composition, to adapt to their ever-changing internal and external environment. When extracted they also undergo subtle chemical changes, turning it into an essential oil. Essential oil may comprise of hundreds of different chemical compounds, all of which contribute to the characteristic aroma and specific therapeutic properties. Those from flowers are much more complicated than those from leaves for example. Flowers can have 12-100 components. Leaf essential oils have only one.

Aromatherapy involves the therapeutic use of isolated plant principles, such as essential oils and, as such, may be considered a branch of phytotherapy. Phytochemistry (a specialised branch of pharmacy) is, in the strict sense of the word, the study of phytochemicals - these are the chemicals derived from plants. In a narrower sense these terms are often used to describe the large number of secondary metabolic compounds found in plants, e.g. essential oils. Aromatherapists use them in the natural “mixed” state (when they are called Terpenoids, because terpenes are present in the greatest quantity). A chemist can break down the oil into its separate components of terpenes, esters, ketone etc of which it is composed and extract the part they want to use

e.g.      Thymol is taken from Thyme essential oil

            Menthol is taken from peppermint oil

We are familiar with both of these substances in present day medicine but probably did not realise that they were from the actual essential oil produced from a plant. The more the essential oil is interfered with chemically or physically, the more its therapeutic powers are reduced.

Essential oils are chemical mixtures that are principally made up of hydrogen, carbon and oxygen covalently bonded together.  The simplest covalently bonded molecule, within essential oils, is a five carbon atom chain, but equally, much more complex chemical structures can also be formed. Therapeutic properties of the main chemical (functional) groups found in essential oils:

 Chemical group

 Therapeutic properties indicated


Antiseptic (esp airborne bacteria) bacteriacidal, stimulating, expectorant, anti septic, anti viral, anti fungal, diuretic, insecticidal


Anti inflammatory, analgesic, hypotensive, sedative, anti viral, antispasmodic, bacteriacidal


Highly bacteriacidal, anti infectious, anti viral, diuretic, immune boosting, least hazardous essential oil constituent


Anti spasmodic, calming, anti inflammatory, anti fungal, relaxing yet uplifting


Considered nuerotoxic (but no proof) so used in dilution (1%) for short periods of time, calming, sedative, mucolyptic, cytophylactic (skin healing)


Mucolyptic, expectorant, anti spasmodic

All these different chemicals exhibit a wide variety of therapeutic benefits and it is the knowledge and skilful blending of these chemicals (working together synergistically) which enable bespoke aromatic products to be created for individuals and their unique issues.

Methods of Application

Essential oils are primarily absorbed into the body in two ways, via the skin or by inhalation via the olfactory system.

The Skin (The Integumentary System) 
Essential oils are a complex blend of aromatic molecules with healing properties. Some of these molecules are so tiny that they have the ability to pass through the skin and into the bloodstream, which then allows them to circulate throughout the body, however as these components are very powerful, the Essential oil is too concentrated to be used directly on the body so they must be diluted in a vegetable carrier oil or other base before being applied to the body. Essential oils may be applied to the skin using the following methods:

  • Massage: a base of a suitable carrier oil, cream or lotion is blended with a few drops of either a single essential oil or synergistic blend of essential oils and applied to the body or used to massage the body, allowing the aromatic molecules to penetrate the skin.
  • Compresses: a few drops of selected oil(s) are added to a small quantity of water (either warm or cold). A cloth is soaked in the aromatic water then applied to the affected body area to use as a compress.
  • Bathing: general bathing, sitz baths, hand or foot baths. A few drops of essential oil(s) are diluted in salts, dispersants, powders or milk. Essential oils can also be added to an unscented shower gel for use in the shower and also to unscented shampoo of natural organic ingredients.

The Respiratory and Olfactory Systems (the sense of smell) 
Aromatic molecules in essential oils are inhaled through the nose and transmitted, via the olfactory bulb, to the limbic system in the brain. This is the part of the brain which influences the nervous and hormonal systems, and which is connected to higher functions such as memory and emotional behaviour. However, as the aromatic essential oils are breathed in, some of the aromatic molecules may also be absorbed through the lungs, and ultimately crossing over into the bloodstream. It is important to remember that each essential oil is actually a complex blend of many different aromatic molecules. These aromatic molecules combine together to create a distinctive fragrance and specific healing properties for each individual oil. Essential oils are inhaled via the following methods:

  • Direct Inhalation: a smelling strip, or a bottle of undiluted essential oil is held about 10cms below the nostrils and several deep in-breaths allow the aromatic molecules to be taken in through the nose up into the limbic brain.
  • Dispersion: essential oils are sprinkled or sprayed onto bed linen, furniture, tissues and handkerchiefs, allowing the aromatic molecules to be inhaled. Used as room sprays.
  • Evaporation: a few drops of essential oils are combined with water and placed over a safe heat source. Heat causes the volatile aromatic molecules to diffuse into the atmosphere for a subtle form of inhalation. Burning essential oils is an effective way of disinfecting the air and of repelling unwanted insects.

Cost of Producing Essential Oils 

The more oil glands or ducts present in the plant, the cheaper the final cost of oil. Oils from plants with few oil producing glands are necessarily more expensive. For example:

100 kilos of eucalyptus yield about 10 litres of oil 
100 kilos of some varieties of rose petals can yield up to 0.5 litres of oil 

The cost of producing essential oils is not only in direct proportion to the quality of the plant but also dependent on the quality of oil-producing glands present in the plant.

Storage of Essential Oils

Essential oils are volatile natural chemical compounds that are susceptible to changes in the environment in which they are stored. They react and change composition in the presence of light both natural and artificial, temperature and containers that the oils are stored in. Essential oils particularly the citrus oils and ones with a high terpene levels and herbaceous oils deteriorate very quickly in the presence of oxygen in the air, sunlight and higher ambient temperatures. The ideal conditions are to store oils under 20°C  in dark glass bottles stored in a dark dry cupboard. Some precious oils can be stored in a domestic fridge at 5°, they may thicken but can be warmed in the palm of your hands to melt them ready for use.

Containers are really important too as they can impact the composition of the finished product. You need to ensure that whatever you store essential oils in they are the right vessel for the oil. The same goes for Vegetable carrier oils although there is more flexibility with carrier oils as they are more inert. Aromatherapists usually use coloured glass such as amber, blue, green or especially spray coloured to suit your branding. The darker the glass the better. There is a violet/black glass that has the best light protection but they are expensive containers to consider. If the volume of oil stored is considerably bigger, aluminium with a lacquer coating on the inside is the best up to about 10-15kgs after which lacquered metal drums should be used. Plastic is not to be used for long term storage of pure essentials oils as not only do they interact with the plastic material causing the container to bulge or retract, the interaction of the plastic with the chemicals of the oil can cause a change in the composition of the oil and small traces can be picked up in the oil.

Closures are important too, preferably tamper proof to protect against accidents with children. Normally essential oil bottles use closures that are fitted with integral droppers or restrictors to prevent the oil rushing out of the container. You can also use wadded screw caps that restrict the exposure of the oil to the air which contains oxygen and causes deterioration and oxidation of the oil. It is also worth remembering that in a large container, as the level goes down there is a greater volume of air above the oil and this leads to oxidation, evaporation and general deterioration of the oil. The best thing to do in this situation, is to decant the oil into smaller containers until it is finished.

The presence of light, sunlight or lightbulbs causes a speeding up of the deterioration of the oil, hence the use of dark coloured bottles. Artificial light contributes to deterioration at a slower rate but are still responsible for this. Always keep essential oils well away from naked flames, heating elements and any spillages must be cleaned up as they happen to prevent build up of the vaporised oil which can then lead to explosions. Essentials oils are highly flammable so make sure they are stored safely!

Taking all this in to consideration, bottled essential oils have differing shelf lives. Most will have a expiry date of 3 - 4 years, however check for expiry dates on the label or box. Citrus oils tend not to last as long, even when kept in the ideal conditions, normal shelf life being 12-18 months. It is always better with these oils to buy in smaller quantities and more often to keep them fresh. With carrier oils the same applies but carriers can oxidise quickly with odd odours, “chip fat” smells that relate to the oils rancidity. Generally, carrier oils last between 6-18 months providing they are stored in optimal conditions. The rule to follow is the guidelines that your suppliers give and to source and find professional suppliers. Do not compromise on quality when choosing your oils for your practice.