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Properties of Good Quality Essential Oils

by Lowana Veal(more info)

listed in aromatherapy, originally published in issue 76 - May 2002

Aromatherapy can work wonders, but it is important to use good-quality essential oils. Unfortunately, many essentials oils on the market are adulterated with synthetic components, and these will not give the same results. Low-quality, adulterated oils give aromatherapy a bad name, as the user, on finding that the oil did not perform as expected, could easily discard aromatherapy per se and say, "It doesn't work". So how do you find out if an oil is adulterated or not? It is not easy to tell – companies are hardly likely to advertise the fact, and some companies have become very adept at adulterating – but you can increase your chances of buying a good-quality oil by scrutinizing the label or catalogue. Although no single one of these attributes will ensure that the oil is good quality, it is probably true to say that the more you find, the greater the likelihood that the oil is good quality. If you can't find the quality you want in your local neighbourhood, investigate mail-order options (phone the company first and see if they seem knowledgeable) or use the Internet to try to identify what you want.

The author picking sage for distillation. The sage from this area is low in ketones
The author picking sage for distillation.
The sage from this area is low in ketones

Quality Indicators

Latin Name

The first thing to look for on a bottle is a Latin name. 'Marjoram', for instance, could be either sweet marjoram (Origanum majorana) or Spanish marjoram (Thymus mastichina). The former has more uses, contains completely different constituents and is more expensive than the latter, and yet Spanish marjoram is often sold as sweet marjoram as it is cheaper. If you have read about marjoram in an aromatherapy book, chances are that you have read about sweet marjoram. See the section on eucalyptus oils for more on this topic.

Chemical Constituents

Some plants vary considerably in their main chemical components, even within a relatively small area, due to environmental factors such as altitude. This is particularly the case with thyme and rosemary. When this happens the oils should be labelled with the appropriate chemotypes. Unless thyme plants are grown from seed, in which case they are called 'population thyme' and contain mostly thymol, thyme oils may vary in their main chemical constituents depending on the altitude at which they grow: those with the gentler components (alcohols) grow at a higher altitude than those with the more aggressive components (phenols). There are at least six chemotypes of thyme and the effects vary considerably, especially between those that are mainly phenols and those that are mainly alcohols. Ideally, where relevant, the label should identify the chemotype, e.g. Thymus vulgaris ct. thymol or Thymus vulgaris ct. linalool. Some companies label those containing mostly alcohols 'sweet thyme' and those with mostly phenols 'red thyme'. If you want to use thyme oil for a specific reason, you really need to know what sort of oil you have.

Butterfly (Scarce Swallowtail) on lavandin
Butterfly (Scarce Swallowtail) on lavandin

Country of Origin

The country of origin is another important factor, and should also be on the bottle. Both the aroma and chemical constituents can vary widely depending on country of origin, due to differences in environmental and climatic conditions. For instance, Bulgarian lavender is thought to be better than French lavender for migraines, and English-grown Roman chamomile better for insomnia than Roman chamomile grown elsewhere.

Part of Plant Used

The part of the plant from which the oil is obtained should also be specified. 'Cinnamon' oil, for instance, can be derived from either the bark or the leaf, but the two oils are very different both chemically and in terms of therapeutic properties. The bark oil contains about 75% cinnamaldehyde, is a strong sensitizer, and is not recommended for use on the skin. The leaf oil is gentler in some senses, although the high eugenol content in the oil means that it is a potential irritant.


Price can also be an indicator. Check the label carefully if pure jasmine, neroli, rose or melissa (lemon balm) oils are cheaper than £25 for 3mls. A blend of lemony oils is often sold instead of melissa, although the label may still say 'melissa'. The expensive oils are often sold as a 5-10% dilution in vegetable oil, which makes the oil cheaper but reduces its versatility. Rose can be found more cheaply in the form of a solvent/alcohol-extracted absolute, but the steam-distilled oil (often known as rose otto) is the more therapeutic of the two.

Batch Number

If there is a batch number on the bottle, the oil is likely to be of good quality and to have undergone some chemical analysis that can then be correlated with the batch number. This is especially important if you intend to carry out some clinical studies or other research work, as if the batch numbers are the same you will know that the oils are the same.

Gas Chromatography/Mass Spectography Readouts

It can be useful if gas chromatography/mass spectography (GC/MS) readouts are available for the oil, especially if you are looking for a particular oil that has a high (or low) content of a particular component. Although these are unlikely to be available in shops, you may be able to get GC/MS readouts from good companies by mail order or if you order via the Internet. It has been noted, though, that some companies that offer readouts only offer mediocre oils.

'Best Before' Date

Some companies put 'best before' dates on their oils. While this is useful for the citrus oils, which have a short shelf-life yet may have been standing for a long time in a shop, there is some disagreement over the shelf-life of many oils, so many good companies do not bother with a 'best before' date. So although a 'best before' date indicates good-quality oil, lack of one does not mean that the oil is mediocre.


Do not be fooled by words such as 'pure', 'natural', 'genuine' or 'authentic'. Virtually all essential oils are labelled as such, but that does not mean that the oils are good quality. A 'pure essential oil' may be pure but may be made up of more than one essential oil or be low-quality oil due to unfavourable environmental parameters. And sometimes oils are adulterated at the distillation plant so the company buyer doesn't actually know about the adulteration. Good companies - and these will inevitably be the smaller ones - will visit their suppliers and make sure that this sort of practice doesn't happen.

Organic Oils

Finally, if you can find a company selling organic oils that also fits all the above requirements, use them as some pesticide molecules somehow manage to end up in distilled oils (and in expressed oils from the peel). Failing that, go for wild-crafted oils if you can. Be aware, though, that not all organic oils are high quality, as adulteration may still exist and some oils may not be grown under optimal environmental conditions, thus leading to inferior quality oil.

A field of Lavender
A field of Lavender

Use in the Home

So once you've bought your good-quality oils, what can you do with them?

Oils for Concentration

A good uplifting blend to help concentration is a mixture of lemon and rosemary oils, perhaps a few drops of each (with water) in an aroma lamp. I used this blend frequently while writing my dissertation. If you are at work, or perhaps working in a library, you can use the same oils by putting a few drops on a tissue inside an empty film canister, and opening the canister and sniffing whenever you feel the need. Enclosed in such a small space, the oils will retain their scent for a long time.

Oils for Sleep Enhancement

Many people use oils, especially lavender, to make them sleep, and indeed a number of studies have been carried out that confirm the beneficial effect of lavender on sleep disorders. However, other oils can also be used as well as lavender for this purpose. A mixture of lavender, roman chamomile and sweet marjoram works very well if you find your mind keeps racing when you're trying to sleep. I have used this in the ratio of 50:40:10 respectively and put a drop on my pillow before going to bed.

Oils for Stress

If you are stressed out, try using a mixture of 2 drops lavender, 2 drops roman chamomile and [1] drop geranium in an aroma lamp, or get someone to give you a massage with the same oils blended in 10-20mls carrier oil.

Use in Hospitals

The use of aromatherapy in hospitals is becoming increasingly common, both in Britain and elsewhere. At the university hospital in Munich, essential oils have been used for about nine years. Initially they were only used to scent rooms. But after a tea tree footbath was successfully used to treat a festering wound on a patient whose foot was due to be amputated, the hospital realized that essential oils were a force to be recognized and now they are used in gastroenterology, cardiology, endocrinology, surgery, nephrology, orthopaedics, intensive care, gynaecology, oncology, dermatology and pain wards. A total of 150 oils are used at the hospital. Where a wound is concerned, aromatograms are done to identify which bacteria are present and what essential oils can be used to treat the wound. A blend of up to five suitable essential oils is then made up by the hospital pharmacy and applied to the wound. Photographs before and after treatment are also taken.1

In other wards at the same hospital, a mixture of cumin, aniseed, fennel and lavender is used for patients with excretory problems; a blend of rosemary, geranium, lavender and palmarosa is used to prevent bed sores with elderly people; rosemary is used for disorientation; a strong solution of lavender, tea tree and palmarosa is used for irritated skin; and lavender or peppermint are used neat on 1st and 2nd degree burns.[1]

The John Radcliffe Hospital in Oxford has pioneered the use of essential oils in midwifery and an extensive research study has been carried out there on the 8,000 women who had chosen to use aromatherapy during labour between 1990 and 1998. Of the women who had used aromatherapy to relieve fear and anxiety (which are known to contribute to the pain factor) 50% found it to be effective, lavender and frankincense being the most popular oils chosen. Peppermint was used successfully to treat nausea caused by pain-relieving drugs, while clary sage and chamomile (probably roman chamomile) were effective in pain relief.[2]

Eucalyptus Oils

Eucalyptus is a useful genus that has been the subject of considerable research. Although Eucalyptus globulus is the most common oil sold in shops, other varieties of Eucalyptus also exist that vary in odour, chemical constituents and activity. In addition, there is also the 'Eucalyptus oil' found in 50ml bottles in chemist shops, which is different again as it is a rectified oil that must, according to pharmaceutical standards, contain 80-85% 1,8-cineole. This oil can be made up of oil from several Eucalypt species. Research studies do not help in this respect, as often only the word Eucalyptus is used and one is left wondering, which one? So what are the differences between the oils? Here is a short summary.

* Eucalyptus globulus contains mostly cineole. There are four subspecies of Eucalyptus globulus and the cineole content varies accordingly, from 33-90%. It is a very good expectorant and antiseptic;[3],[4]
* Eucalyptus smithii also contains a high concentration of cineole, approximately 70%, but its other components counteract this and it is often recommended for children as a gentle alternative to Eucalyptus globules;[5]
* Eucalyptus citriodora has a distinct lemony odour and typically contains 85-90% citronellal. It should be used with oils high in monoterpenes or monoterpene alcohols in order to quench the irritating nature of the citronellal. It can be used as an insect repellent and is also a good antiseptic, but should be used sparingly as the odour tends to be overpowering;[3]
* Eucalyptus staigeriana has a subtle lemony odour yet is a very powerful oil. It is analgesic, antiseptic, calming and good for sinus decongestion, and should be used either as the dominant note or in a small dosage. No one constituent predominates.[3],[6] It is one of my favourite oils.
* Eucalyptus radiata occurs in two forms, one with 65-85% cineole, the other more balanced with piperitone, cineole (a-phellandrene and p-cymene as its main components. It is good for catarrh and is also a good expectorant;[3,4]
* Eucalyptus dives has a peppermint odour. There are two chemotypes, one of which contains 70-80% cineole while the other contains about 50% piperitone and 20% (a-phellandrene. Both types are good for respiratory ailments;[3]

Eucalyptus oil is a good example of one for which it is important to know the scientific name and have a GC/MS readout for the oil. Unfortunately, this is not usually the case. Research by scientists who say "Eucalyptus oil added to detergent kills almost all house dust mites during machine washing of blankets"[7] really isn't very helpful. In this instance, one would hope that the oil used is the cheap rectified oil, otherwise household washing would turn out rather expensive as 100ml eucalyptus oil was used each time in the tests.


In essence, essential oils are highly concentrated chemicals so it is not surprising that they, or at least some of them, are contraindicated in some instances.

* Young children. Under-fives should not be exposed to oils except for small doses of lavender, roman chamomile, palmarosa, sandalwood and mandarin;[8]

* Allergies. Those who have an allergy to plants from the daisy family should avoid those essential oils, namely the chamomiles, yarrow and tagetes but also calendula carrier oil, due to the risk of cross-sensitization and allergic reactions;

* Exposure to sun. Tagetes is also highly phototoxic so, like all phototoxic oils, should not be used on the skin within 12 hours of being exposed to sunlight. Other common phototoxic oils include bergamot, angelica root oil, cumin oil and, to a lesser extent, other oils from the citrus family;

* Pregnancy. A number of oils should be avoided by pregnant women unless they are about to give birth. Some people take the view that essential oils should not be used during pregnancy unless they have definitely been proved safe, while others take the opposite viewpoint. Hence there is disagreement on which oils should be avoided, and why.

Nevertheless, most would agree that neurotoxic oils – yarrow, aniseed, tagetes, caraway, hyssop, wormwood, rosemary and pennyroyal – usually have a high concentration of certain ketones, phenolic ethers or 1,8-cineole5 and should be avoided by pregnant women due to potential adverse effects on the foetus. Oils that are known or suspected to be emmenagogues should likewise be avoided, due to the possibility that the oil could induce a miscarriage. These oils include tagetes, aniseed, sage, sweet fennel, niaouli, yarrow, cinnamon bark and nutmeg. However, some of these oils, such as sweet fennel, can be used during the birth itself to stimulate uterine contractions. A detailed discussion on oils known or suspected to be contraindicated in pregnancy can be found in Price and Price.[[5]

* Epilepsy. Oils containing cineole, sabinyl acetate or various ketones, such as camphor, pinocamphone, thujone, pulegone and fenchone, are contraindicated for use by epileptics.[9] This means that cineole-containing eucalyptus oils, fennel, pennyroyal, hyssop, wormwood, rosemary and sage should be avoided by them. Although the doses used in such experiments and case studies were much larger than those normally used in aromatherapy - who in their right mind would ingest a mouthful of essential oil weekly for several years to cure hyperlipidemia? – other experiments have shown that epilepsy can be triggered in some people by prior exposure to very small doses of the essential oil.[9]

Generally, though, essential oils are safe if used sensibly. Be aware that most studies indicating toxicity have involved the ingestion or use of relatively large quantities of the oil, much more than is usually used in aromatherapy. Remember also how many people die from the effects of allopathic drugs (which of course is played down by the medical profession) and from interactions between drugs. Essential oils may not be able to cure serious diseases such as cancer, but there is a lot that they can do. Use them wisely.

Comments from the Industry

Shirley Price Aromatherapy Ltd

The only true ‘manufacturer’ of true essential oils, is the plants themselves. The quality of the resultant oil is dependant on where and how the plants are grown in terms of:

• location and height
• in sunshine or shade
• whether watered by rainfall or irrigation
• whether fertilisers and pesticides have been used
There are also the added variables of:
• how and when the plants are harvested
• if the plants are distilled fresh or dried
• for how long the plant material was distilled

Because the quality and wholeness of any essential oil is paramount to its effectiveness, the sourcing of such oils is a major priority. Essential oils offered through most wholesale suppliers have been produced for the perfume or food industries, where adulteration is common practice; commercial traders add other, cheaper oils, or synthetics to genuine oils in order to maintain the same standard of taste, aroma and price for their main buyers.

The most accurate method of testing the quality of essential oils is by GLC; there needs to be an experienced reader of the GLC printouts on the premises to determine whether or not the essential oil is genuine. This is not easy because of the natural variability in essential oils; no natural chemical is present in the same proportion from every yield. However, variability can also be reassuring – no synthetic would vary in content.
It is impossible for the ‘ordinary’ person to determine the quality of any given essential oil; even the experienced aromatherapist ultimately has to trust his/her supplier. Following are a few suggestions that are, unfortunately, not foolproof or even to be recommended.

• Is it likely that ‘pure’ rose essential oil at £2.50 for 10ml is a good buy?
• Check the viscosity: some essential oils are thick and should not run out easily.
• How does it smell? A basic check, although often the least accurate.
• Evaporation: essential oils will evaporate completely, occasionally leaving a stain, but they do not leave an oily residue.

Choosing and purchasing essential oils depends on a trustworthy supplier. This information should be available:
• botanical name
• country of origin
• plant material used
• method of extraction
• batch number and testing policy

All reputable suppliers should be happy to answer your queries.
Penny Price, Training Manager
Shirley Price Aromatherapy Ltd

NHR Organic Oils

We start by building a personal relationship with our suppliers, be it the farm that grows the original organic plant e.g. organic lavender in the fields, or the distiller who buys this plant material and actually distils and creates the oil. We then use our thorough testing program to choose an individual organic essential oil once it arrives at our premises.

Our testing facilities include the most up to date GC-MS (Gas Chromatography – Mass spectrometry) laboratories in the UK and in France which can detect down to 0.001% trace substances. Each oil is individually tested to detect the exact proportion and quantities of correct components. For example with organic lavender we check that the oil contains a proportion of esters ‘exprimes’ in linalyl acetate varying between 35 and 55 p 100. We check there are no adulterants or chemical residues, to ensure that the source of growing is from a certified organic farm. We have reports of extraction methods, and farming techniques, keeping a close check on the crop quality and harvest over the whole season.

We then meticulously examine the oil for Colour Consistency. Highly important, it indicates just how pure and balanced the oil is, a lost art in the aromatherapy world, due to the use of brown glass bottles which hide the oils’ colour.

Viscosity – how the oils feels on the skin. Texture and consistency indicates the quality of the extraction method and therefore quality of the oil.

Aroma – we carefully evaluate the aroma for its full note range to select the purest and most balanced oils amongst the batch being tested.
Kolinka Zinovieff, Director NHR Organic Oils
Tel: 0845 310;

Tisserand Aromatherapy

Packaging: Look at the dispenser on the bottle – it should be a dropper. Take into consideration the viscosity of the oil.

Fragrance: should be clear, precise and with lots of vitality.

A supplier that has restrictions on the purchase of some essential oils shows an understanding of safety and toxicology for the therapist and the public at large.

Yardsticks to look for should include the following points:

  • Heritage of the company supplying the oils – look for a company who specialises in their field and not a jack of all trades;
  • Always check out the supplying companies guarantees of the quality of essential oils; they should have certificates of purity.
  • Lastly it is important to realise that it doesn’t matter if the therapist is buying oils to blend herself versus buying the ready blends because where they find the former they’ll find the latter.

Clive Walker – Marketing Director of Aromatherapy Products Ltd
Tel: 01273 325666;


1. Demleitner Margaret. Scientific Research in Europe on the Curative Power of Plants. Conference Lecture. Reykjavik. March 2001.
2. Burns E, Blamey C and Ersser SJ et al. The use of aromatherapy in intrapartum midwifery practice – an observational study. Complementary Therapies in Nursing and Midwifery. 6(1): 33-34. 2000.
3. Webb MA. Bush Sense – Australian Essential Oils & Aromatic Compounds. Mark Webb. 2000.
4. Lis-Balchin M. Aroma Science – The Chemistry & Biochemistry of Essential Oils. Amberwood Publishing. 1995.
5. Price S and Price L. Aromatherapy for Health Professionals. Churchill Livingstone. London. 1995.
6. Marshall F. Personal Communication. 12 July 1997.
7. Tovey ER and McDonald LG. A simple washing procedure with eucalyptus oil for controlling house dust mites and their allergens in clothing and bedding. Journal of Allergy and Clinical Immunology. 100(4): 464-66. 1997.
8. Styles JL. The use of aromatherapy in hospitalised children with HIV disease. Complementary Therapies in Nursing and Midwifery. 3(1): 16-20. 1997.
9. Burkhard PR, Burkhardt K and Haengeli C-A et al. Plant-induced seizures: reappearance of an old problem. Journal of Neurology. 246: 667-70. 1999.


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About Lowana Veal

Lowana Veal, MSc, is a research biologist who has lived in England, Australia and Iceland. She has researched the use of essential oils as a means for killing head lice and more recently has initiated a project looking into genetic variation of juniper in Iceland. She has also researched the medicinal properties of birch and larch trees. She has done two short aromatherapy courses and is an active participant in two aromatherapy mailing lists on the Internet, one a general list and the other a research list. She can be contacted at


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