Essential oil safety-The known and the unknown.

By Martin Watt

For many years a large volume of scientific information has been available on the safety of essential oils. Many essential oils have been used for over 100 years as ingredients of: medicines, food, drink, perfumes, cosmetics, soaps, detergents, candles, industrial applications, etc. Due to this widespread use, various authorities around the world, have investigated the safety of the oils in most of their commonest applications.

Sources of information.
The World Health Organisation publishes papers on the maximum levels recommended in foodstuffs. Their deliberations are ongoing and from time to time new reports are issued. The Council of Europe publishes similar guidelines. The FDA in the United States has lists of GRAS status ingredients for foods which include some essential oils. Most countries have their own legislation regulating the most dangerous oils and in that regard the UKs 1968 Medicines act does that. (See later).

How do these organisations assess the safety or otherwise of essential oils? Well they have many sources of information to draw on, or if they are uncertain, they will commission independent studies. Many essential oils were listed in several National pharmacopoeias around the turn of the Century because they were commonly used in medicinal preparations. However, subsequently a significant amount of scientific investigations have been undertaken, particularly in many universities around the world. Some of this work has been co-ordinated for regulatory authorities, and some experiments simply for independent academic studies.

The best source of safety information of relevance in aromatherapy is the R.I.F.M. (Research Institute for Fragrance Materials) and their sister organisation the I.F.R.A. (International Fragrance Research Association). These organisations collect data in a number of ways: they gather scientific information and assess it, member companies report adverse reactions to fragrance materials to them, and if necessary, they in turn circulate member companies with warning notices. Finally, they have commissioned significant research evaluations of fragrance materials. For well over 30 years, these organisations have published their findings, in an extensive series of monographs on essential oil safety in the journal- Food and Chemicals Toxicity.

The fragrance trade organisations do sterling work gathering data from adverse reactions reports and from testing the material in clinics around the world. The aromatherapy trade has no such system to monitor adverse effects of raw materials.

Legal considerations.
Before embarking on the known hazards of using essential oils, we should look at existing law relating to the sale and supply of essential oils.

Under UK and EEC law, it is an offence to place any product on the market if known hazards may be associated with misuse or inappropriate use of the product. That is unless 'appropriate warnings' are attached to the product. Despite that, many traders here do still ignore this important piece of consumer protection legislation. 'Appropriate warnings' is the most important issue. There is nothing wrong with selling many of our most hazardous oils for non-contact uses, i.e. in fragrance heaters, pot pourii, candles, etc. However, it is unscrupulous to not warn people that these products should not be applied to the skin, and also probably illegal.

The legal position of anyone that uses oils with known dangers, in a professional setting, such as in an aromatherapy treatment, requires examination. If someone used such a substance, and their client suffered a side effect as a result. Such a client would have an extremely powerful legal case to argue. Where a major research organisation such as RIFM, has advised the large fragrance companies against the use of such materials for many years, then in such circumstances, a court might deem it unreasonable, for a qualified aromatherapist to use the material in an 'inappropriate manner'. Here I am particularly thinking about oils like expressed bergamot, where if used in a health club, before someone goes under the sun bed, could cause a very severe skin reaction.

It is also highly likely, that if the therapist did this, then their insurance company would refuse to stand by them and cover any subsequent damages awarded.

Banned or restricted oils.
The only essential oils that are prohibited for resale to the public under the UK 1968 Medicines Act are: Chenepodium (American wormseed), savin oil and croton oil. These oils may only be distributed to the medical profession from licensed pharmaceutical premises.

Another oil that is 'effectively' banned in cosmetic products is sassafras oil. By 'effectively' banned this is because the E.E.C. only permit safrol in products at below at 100 ppm. Since raw sassafras oil contains about 870,000 p.p.m. of safrole, this means that in aromatherapy you would have great difficulty in diluting the oil to a safe and LEGAL level of use.

Countries within the European Community vary considerably in which essential oils can or can't be sold, and how they may be used. However, once the oil is introduced to a product formulation, the laws are now almost standardised.

Adverse reactions
The 3 main kinds of adverse reactions that can occur with essential oils applied to the skin are:

1. Irritation. This is a process where some substance comes into contact with the skin, and causes anything from a mild itch to burns. The important thing though it that once the substance is removed and healing takes place, there should be no more problems.
2. Sensitisation. This is a much more serious situation than irritation. Once the substance has been introduced to the skin, it can cause permanent changes in the immune system in a similar manner to a vaccination. On first use no adverse effects may be seen. However the body has been sensitised, and next time the same or a similar substance is used, a reaction may occur. The severity can again be just a mild itch, through to the extreme of severe anaphylactic shock. However, the later in aromatherapy is almost unknown. Sensitisation in aromatherapy is something to be on constant alert for. If after using any essential oil or absolute, an irritating or burning sensation, or a blotchy irritable skin rash are noticed, then that particular oil or chemically similar ones should not be used again. This type of reaction is far more likely to occur with therapists rather than their clients.
3. Photosensitisation (sometimes referred to as phototoxicity). This is where a substance coming into contact with the skin can react with ultra violet light. This reaction can cause anything from mild brown blotches through to severe burning of the skin. The condition can be very long lasting and any time the skin is exposed to ultra violet light the condition can recur. It is vital to remember that it is ultra violet light which causes the problem and this can occur even on relatively dull days. Therefore it is not as many aromatherapy authors say caused only by bright sunlight. The main essential oil to avoid in this respect is expressed bergamot. The grade known as FCF is perfectly safe.

Miscellaneous claimed adverse effects.
Pregnancy. Almost all of the claims made in aromatherapy books about not using certain oils during pregnancy are unfounded. Many such claims are based not on the essential oil concerned, but are from the traditionally claimed effects of the water soluble herbal extracts when taken internally. Such extracts are frequently totally different to the same plants essential oil.

The facts are that most common essential oils are permitted food flavourings. If there were the slightest evidence that using essential oils externally was any threat to the health of a foetus, then the oils concerned would have been restricted by legislation long ago.

If someone was suffering from severe morning sickness early on in pregnancy, then the smell of something like peppermint or spearmint oil may well subdue the nausea. In such a case of constant vomiting, the implanted foetus is far more likely to be dislodged by the traumatic muscular contractions of the uterus, than from the effects of the inhalation of ANY essential oils.

The birch and wintergreen oils are best avoided during pregnancy. This is because indications are that the main chemical is readily absorbed by the skin. High levels of this in the bloodstream are not desirable in pregnancy.

Clary sage is perfectly safe in a normal pregnancy, but should perhaps be avoided by anyone with a history of early miscarriages.

The main contra-indication of essential oils use during pregnancy is the heightened chance of causing skin irritation. It is quite common in late pregnancy for the skin to become very itchy and sometimes inflamed. In such circumstances essential oils in massage or the bath might make the condition worse.

Epilepsy. There is no sound scientific evidence that any particular essential oils can trigger an epileptic incident. In fact it is well documented that any powerful smell can initiate such an attack. Therefore the only advice may be avoid the pungent oils like camphor, eucalyptus, tea tree, rosemary, etc. On the other hand, some trials have indicated that the traditionally relaxing oils can substantially reduce the incidence of attacks.

High or low blood pressure. There have been no scientifically verified trials published, following the external application of oils on humans, where blood pressure has been monitored. There are no proven cases, of anyone who has suffered ill effects from an escalation of blood pressure caused by aromatherapy. Indeed the opposite is likely, which is that a nice relaxing massage, or the use of the oils as room fragrance, will decrease a blood pressure that is high due to stress.

Sell by, or use by dates.
This is an important piece of safety information to take note of. Certain essential oils, particularly those of the citrus and pine families, develop skin sensitising chemicals as they age. Without analysis, one can not be certain how quickly oils have aged. Therefore as a general rule, I advise people not to use such oils on the skin after about 6 months. They can of course still be used for room fragrance purposes. Storing such oils in optimum conditions, such as in sealed containers in a refrigerator will slow down the chemical changes in the oil.

The use of little known 'chemotypes' and completely untested essential oils.
The vast majority of our commonest essential oils have been well tried and tested and safety levels have been ascertained. However, when an aromatherapist uses oils whose safety has not been adequately ascertained, they are actually using their clients as human guinea pigs. Unless a client is told that the safety of such oils is unknown, then this is certainly unethical and possibly could leave the therapist open to legal challenges if things went wrong.

Many of the 'untested' oils are said by some people to have been "used traditionally". However, when this statement is carefully checked this is often found in error. The reason is that what has been used traditionally is the HERB not the oil. Herbal preparations contain totally different chemicals, with often totally different actions, to those occurring in a distilled oil from the same plant. Therefore such so called 'traditional' uses may not have any basis in fact.

There are some compounds occurring in plant oils that can cause sensitisation reactions when only occurring at a few parts per million. Therefore chemical analysis of the major compounds occurring in the oil can give absolutely no guide as to its safety. Examining the major chemicals in an oil to judge efficacy and safety is a major error, but forms a major part of the teachings of certain aromatherapy teachers. This problem largely originates from certain well known French therapists. If it were possible to judge safety by such means., then large organisations specialising in safety would not need to have spent millions on animal and human trials.

How is testing done.
Testing for toxicity is all done on animals, you are not allowed to do this on humans because it's called murder!! Most of the testing was done in the early 1970s. However, animal testing of essential oils and their components still does happen occasionally, mainly in Universities. The toxicity of a few oils in humans, has been documented from past cases of poisoning.

Skin adverse effects. Some of these tests were done on animals, but the final testing was on humans. These kind of tests are still conducted on volunteer panels of humans. In addition specialist dermatology clinics around the world, test people they think may be allergic to fragrance compounds, as part of their routine testing procedures. These results are often published in International dermatology journals and add to the wealth of knowledge on the side effects of essential oils.

Some essential oils which you should be cautious about.
The following list is incomplete because there is a never ending flow of 'new' oils being pushed into aromatherapy. It is common to find that scientists have found very good therapeutic properties in some "newly discovered" plant oil. These scientists then appear at International conferences to talk about their findings. The next thing of course is everyone wants to buy this new magical oil. No one, the scientists concerned included, pause to give a second thought to the potential side effects of this wonderful new discovery. Unfortunately it is not until some poor individual has been harmed that someone gives safety a second thought. So the moral of all this is to be safe, stick to those oils the safety of which has been well documented.

• Amni visnaga. No formal safety trials are known.
• Benzoin resinoid and oil-a well documented sensitiser. RIFM recommend only grades processed to remove the allergens should be used in consumer products. These grades are not generally available via aromatherapy suppliers.
• Bergamot oil expressed-a potent photosensitiser-see 'Photosensitisers'.
• Calamus oil. A potential carcinogen, and banned in cosmetics.
• Catnip. No formal safety trials are known.
• Cinnamon bark oil-an extremely powerful irritant and an even worse sensitiser.
• Chamomile moroc. Often labelled just as "Chamomile oil". This oil has not undergone Internationally acceptable safety testing.
• Copaiba or copahu. Can cause sensitisation reactions if it is old and oxidised.
• Eucalyptus chemotypes. The only types that have been tested are the globulus types and E. citriodora.
• Inula graveolens. A related species; Inula helenium-root oil, is one of the most hazardous essential oils available. If the graveolens variety contains the same sensitising agents is not known. Therefore, until such time as formal testing has been done, it is most unwise to use this oil on the skin.
• Kanuka. This oil has not undergone Internationally acceptable safety testing.
• Manuka. This oil has not undergone Internationally acceptable safety testing.
• Melissa. The pure oil has not undergone Internationally acceptable safety testing.
• Niaouli. The pure oil has not undergone Internationally acceptable safety testing.
• Peru balsam-a very powerful sensitiser. RIFM recommend "not to be used as a fragrance ingredient".
• Ravensara aromatica and other ravensara oils. None of these oils have undergone any formal safety trials. There also seems to be a lot of manufactured oil on the market which makes their safety suspect.
• Rosemary chemotypes. Only the common cineol types have been tested.
• Rue oil- a terrible photosensitiser and sensitiser.
• Sassafras. This oil is restricted to such low levels in cosmetic products throughout Europe, that it effectively bans its use. The reason is because tests have shown it is possibly carcinogenic.
• Spikenard. Like it's cousin valerian, these oils have not undergone Internationally acceptable safety testing.
• Tagetes (sometimes mis-described as calendula)-a powerful photosensitiser. RIFM say a no effect level is 0.05%. Therefore to use it on skin exposed to the light would be foolish.
• Tansy oil-extremely toxic, and of little if any use in aromatherapy.
• Thyme chemotypes. Only the common phenol types have been tested.
• Valerian. Has not undergone Internationally acceptable safety testing for adverse effects on the skin, although toxicity has been tested.
• Verbena oil-an extremely powerful sensitiser-recommended by the RIFM "not for use as a fragrance ingredient". Massive percentages of adverse skin reactions are recorded from testing a whole range of verbena oils. There also seems to be a lot of manufactured oil on the market which makes their safety suspect.
• Wormseed (Chenopodium)-extremely toxic. Banned from general sale in the UK because of the deaths reported from its consumption in the past.
• Yarrow. Another essential oil that has not undergone formal safety testing.

If anyone sees such oils on open sale without appropriate warnings, you should tell the vendor that the oils are not safe, or the safety is unknown. Often they may not know, and may have relied for their knowledge entirely on the popular aromatherapy novels, or on some of the appallingly poor training courses around.

Much greater detail on safety is available in the publication "Plant aromatics" by Martin Watt. [That book is out of print as of 2010. As of 2015 there is a new edition of "Essential Oil Safety" by Robert Tisserand available; you can find it on Amazon, or go to the author's website linked in the book title.]

Or email Martin Watt for more information.