Types of Essential Oils – Explained
Essential oils are called essential because they contain the very essence of the plant, or in other words, the intrinsic character of that plant. They are concentrated extracts taken from the leaves, flowers, fruit, seeds, or bark of certain plants that contain the aromatic compounds that give plants their distinctive smell or fragrance. Some oils are used simply for their fragrance. However, essential oils have many other benefits beyond making your home smell pleasant.
Essential oils are used in a variety of ways, including aromatherapy, massage, skin-care, and even cleaning. There are many different types of essential oils available, each with their own unique properties. So what are the different ways of categorising essential oils?
Fragrance
Some essential oils are classified according to their scent or botanical source. These categories are floral, citrus, or herbaceous. These tend to be the oils that are used simply to make your home smell nice, although they are also useful to mask unpleasant cooking, pet, musty or damp odours. One of the most popular ways to use essential oils for their fragrance is store-bought or home-made candles. However, they can also be used in reed diffusers or oil burners.
Floral oils are extracted from the blossoms of flowers and have a sweet, delicate scent. Some popular floral essential oils include jasmine, rose, and ylang-ylang. Citrus oils are made from the peel of citrus fruits such as oranges, lemons, limes and grapefruits. These oils have a refreshing, invigorating, uplifting scent and can be used to boost energy levels (1).
Citrus oils, especially lemon is popular for use in cleaning products. Herbaceous oils are extracted from the leaves or stems of herbs such as lavender, rosemary, and thyme. These oils have a pleasant, clean, earthy scent. Spicy oils such as cinnamon and clove are stimulating and warming, making them ideal for use in cold weather. These oils are often used in Christmas blends for candles and oil burners.
The most popular scents for home use appear to be ylang ylang, chamomile, lavender, and geranium, bergamot, citrus and fruity (2).
Therapeutic
Other essential oils are classified by their therapeutic properties. These can be calming, energising, or uplifting. Essential oils that are often used to help calm, relax and induce sleep are lavender, jasmine, peppermint (3), chamomile (4) and ylang ylang. Energising essential oils include peppermint, which also increases alertness (5), and rosemary, which can have a positive effect on cognition (6) and long term and working memory (7). Similarly, sage essential oil not only increases cognition and improves memory but has also been found to improve memory retention in Alzheimer’s patients (8).
Peppermint oil can help to freshen breath and kill bacteria in the mouth (9), which is why it is often used in chewing gum, toothpaste and mouthwash. It can also help settle an upset stomach, so it is often used in antacid medications as well (10). Eucalyptus oil is well known for its decongestant properties and helps ease the symptoms of coughs and colds (11). It is another essential oil often used in over-the-counter medications such as lozenges, cough syrups and vapour rubs.
Essential oils are viewed by some people as the domain of hippies or witch doctors, not to be taken seriously as mainstream medicines. However, research is beginning to demonstrate that there are many benefits to these fragrant oils beyond just smelling pleasant.
Chemical
Essential oils can also be grouped together based on their chemical composition. These chemicals are what give essential oils their beneficial properties, with some essential oils containing as many as five hundred different chemicals (12).
The most common categories are terpenes, furanocoumarins and phenylpropanoids. Terpenes, which make up the largest group of essential oils, are characterized by their strong, pungent aroma. They are volatile, which means they evaporate easily. Three types of terpene are limonene found in citrus and bergamot oils; cineole found in eucalyptus, rosemary, peppermint and sage (13); and carvone found in dill and caraway (14). Furanocoumarins are another chemical category of essential oils. These compounds give the plants an in-built, natural protection against insects (15). They are also known for their photo toxicity. This means they can make the skin more susceptible to the effects of the sun, so they are best not used on the skin. Lemon, grapefruit, angelica and cumin are phototoxic essential oils. These oils are considered safe in body care products that are only on the skin for a short while and then washed off. For example, soap or body washes (16). These oils should also be used with care when taking other medications, as grapefruit oil, in particular, can interact with other drugs (15). On the other hand, phenylpropanoids tend to be non-volatile (17), unlike terpenes, and tend to have a wide range of scents, from floral to woody. More importantly, safrole found in basil oil, myristicin in nutmeg oil, anethole in star anise and fennel oil, cinnamaldehyde in cinnamon oil and eugenol in clove oil are all examples of phenylpropanoids that have been shown to kill cancer and tumour cells (18). These compounds are also anti-inflammatory (19), which is why the use of essential oils is great for pain relief.
Top, middle and base notes
Essential oils can also be classified as being either top notes, middle notes, or base notes. Top notes have a light, fresh scent and evaporate quickly; they are often used as the first layer in a perfume blend and to brighten a blend. Peppermint, lemon, orange and bergamot are examples of top note fragrant essential oils. Middle notes have a sweeter smell and provide body to a perfume blend; they tend to last longer than top notes and can help to balance the blend of an essential oil mix. Essential oils derived from herbs and flowers, such as tea tree, lavender, rosemary, jasmine and geranium tend to have middle note fragrances. Finally, base notes have the heaviest scent and linger the longest; they are typically used for grounding and relaxing perfume blends. Sandalwood, patchouli and frankincense are base note essential oils (20).
When selecting essential oils, it is important to consider the desired effect and choose accordingly. For example, a blend with a heavier base note might be more suitable for relaxation, while a blend with a lighter top note might be more invigorating. By understanding the different categories of essential oils, it is possible to create blends that are tailored to specific needs.
Ultimately, the best way to choose an essential oil is to experiment and see what works best for you. With so many different types of essential oils available, there is sure to be one that meets your needs.