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Toxic and Restricted Essential Oils

Although essential oils can be used to the great benefit of your general health, it must always be kept in mind that they are potent compounds. There are also some essential oils that should not be used in Aromatherapy.

You shouldn’t normally find any of the oils mentioned on the toxic list for sale commercially, but it is good to know more about them if you do come across them.

Some essential oils have been claimed to be toxic in the past but current suggestions and research show that these oils may be used in Aromatherapy if they are used with extreme caution.

We have made a list of these oils below and have divided this list into two categories because the use of all the oils on this list are commonly discouraged in Aromatherapy:

  • Toxic oils (should not be used in Aromatherapy).
  • Restricted essential oils (can be used in Aromatherapy, but with extreme caution).

This is not an exhaustive list and there are other essential oils around that are also considered toxic or are restricted for use.

We mention the safety guidelines for all the essential oils we sell on the specific products page.

Toxic Essential Oils

A list of essential oils that should be totally avoided because of their toxic effect, with notes on the reason why they are listed.

Almond (Bitter) – Prunus amygdalus var. amara

o Prussic acid – also known as cyanide, is the main constituent of bitter almond oil, and even small amounts can be lethal.
o Almond essence can made from this oil, but only after the prussic acid has been removed with rectification and washed by alkali. Commercial Almond Essence is now mostly made synthetically and is safe for use in any case.

Boldo – Peumus boldus

o The dried leaves are used in herbal medicine, but the oil is powerful and can encourage convulsions. Neurotoxic. Contains highly toxic Ascaridol and moderately toxic levels of thujone.

Camphor (Blue, Brown, and ‘Green’ fractions) – Cinnamomum camphora

o Blue Camphor is the heaviest fraction of camphor oil. Yellow and brown camphor are medium fractions.
o Camphor oil oxidises easily, and oxidation will affect the oil, making it more harmful and a skin sensitizer.
o The Blue Camphor fraction contains the highest level of safrole and the brown Camphor fraction has less. While research is not thought to be totally conclusive, safrole is regarded as being carcinogenic. It is recommended that high levels of safrole should be avoided.
o Blue and brown Camphor oil are rarely available for purchase commercially and should rather be avoided in any case.
o We did limited research into ‘green’ camphor – this seems to be obtained from the resin of the tree and is used in Ayurvedic medicine.
o Reports show that some of the product/s sold commercially claiming that they contain ‘green’ Camphor may be derived from turpentine and is/are not safe for use.
o Conflicting reports found regarding the safety of ‘green’ Camphor.

Horseradish – Armoracia rusticana

o The herbal use of horseradish is apparently effective to treat coughs, yet the oil of horseradish contains high levels of allyl isothiocyanate (as does mustard oil) and this is an extreme irritant to the skin, eyes, nose, and mucous membranes.
o Horseradish oil should not be used in Aromatherapy at all.

Mustard – Brassica nigra

o Although mustard seeds and powder do not contain allyl isothiocyanate, the compound is found in the essential oil. When the essential oil is created through diffusion a glycoside decomposes due to enzymatic action and this forms allyl isothiocyanate in the essential oil.
o This oil is not only toxic because of the high content (92% minimum is usually found) of allyl isothiocyanate, it is an extreme skin and mucous membrane irritant.

Pennyroyal – Mentha pulegium

o The herb has had a long history of use for various complaints, including menstrual problems. It is also used as a stimulant, even though the tisane (tea) of the herb contains pulegone, which is a known toxin.
o The essential oil is highly toxic (high pulegone content) and can cause acute liver damage, even in small quantities.
o It is widely claimed to be an abortifacient. The amount of the essential oil that must be consumed for an abortifacient effect would be highly toxic and case histories show that death and/or severe liver damage often occur/s when this essential oil is consumed for this purpose.

Sassafras – Sassafras albidum

o This herb has been used for rheumatic pains and gout, but the oil is high in safrole (80 – 90%). The essential oil is banned by the FDA since they find it to be carcinogenic (cancer causing). It can be lethally toxic as well – even in small amounts.

Savin – Juniperus sabina

o This oil is toxic due to its content of sabinol and sabinyl acetate, which causes liver toxicity.

o It is an abortifacient and is toxic to the foetus or embryo.

Tansy – Tanacetum vulgare

o Tansy oil is high in thujone. A relatively small dose of Tansy can cause convulsions, vomiting, uterine bleeding, coma, and asphyxiation if consumed.
o Death is normally the result of respiratory arrest and organ failure.
o Tansy essential oil can be used on the skin in extremely low dilutions (0.5% or lower), but the high possibility of poisoning suggests a total restriction of use in Aromatherapy
o Tansy essential oil should not to be confused with Blue Tansy, Tanacetum annuum).

Wintergreen – Gaultheria procumbens

o The active ingredient in wintergreen oil is methyl salicylate (found in levels of around 98% in batches) and although it is used in ointments for rheumatism and other such complaints, pure Wintergreen essential oil is poisonous, prevents blood clotting and is extremely dangerous for people who are allergic to aspirin. We do not recommend keeping this oil in its pure form in the house at all – rather buy a commercial ointment/cream containing Wintergreen and keep this out of the reach of children, pets and uninformed people.

Wormseed – Chenopodium ambrosioides

o The name is linked to the fact that wormseed was used to expel round and hookworms.

o Due to its toxicity to the liver and kidneys, and that it  suppresses heart function, its general toxicity and neurotoxicity (nerves), it is no longer used.

Wormwood – Artemisio absinthium

o The drink absinthe (the drink of choice of Vincent van Gogh) contained wormwood and continuous consumption was said to produce auditory and visual hallucinations, possible addiction and a couple of other unpleasant side effects.
o The active ingredient in Wormwood essential oil is thujone, which is a convulsant and a neurotoxin. o The essential oil also has possible abortifacient properties due to the Sabinyl acetate contents.
o Although Wormwood can be used in extremely low dilutions on unbroken skin, we suggest that this essential oil should not be kept in a house – the risk of poisoning is too great.
o Thujone free Wormwood essential oil can be created which would cancel these side effects – we haven’t come across a firm selling this type.

Restricted Essential Oils

Calamus – Acorus calamus var. angustus

o Calamus tetraploid essential oil (usually originating in India and surrounds) should not be taken internally. It is suggested in research that this form of Calamus is toxic to the liver and is carcinogenic.
o Claims are also found (mainly from India and proponents of Ayurvedic medicine) that this is an overreaction and that the balance between the β-Asarone and the α-Asarone contained cancel out the carcinogenic effect.
o More research is needed, but we must recognise that the FDA prohibits the use of β-Asarone in all medicines and supplements.
o The EU recommends a maximum of 0.01% in products applied to the skin. This is possibly due to the carcinogenic effect of β-Asarone,  but is also possibly due to the presence of methyleugenol in the essential oil.

Camphor (Yellow Fraction) – Cinnamomum camphora

o Although yellow camphor is used in the treatment of certain infectious and respiratory diseases, oral ingestion is regarded as being toxic.
o Yellow camphor fractionated oil does contain safrole, but can be used in extremely low dilution rates on the skin (IFRA recommends a 0.05% dilution rate).
o Yellow camphor fractionated oil is rarely available for purchase and the white Camphor fractionated oil is considered to be much safer for use.

Cassia – Cinnamomum cassia

o This herb is commonly used to treat a series of digestive complaints.
o The essential oil is a dermal sensitizer and it irritates the mucous membranes. Low dilution rates are recommended if used on the skin (0.05%). o The essential oil may contain methyleugenol and should not be used when pregnant or breastfeeding.
o The essential oil also influences blood clotting and interacts negatively with medications.

Mugwort – Artemisia vulgaris

o We have found Mugwort listed as a toxic essential oil in quite a few old reference books, and we also listed this oil as toxic in the past.
o Mugwort (the herb) is commonly used to make beer.
o The herb is commonly used in herbal remedies for anxiety, stomach problems and to balance periods.
o The essential oil of both common chemotypes (chrysanthenyl acetate and camphor/thujone) usually contain moderate amounts of thujone, which is a neurotoxin and can lead to convulsions. o This essential oil should not be used if you have a sensitivity to thujone or when pregnant or breastfeeding.
o We suggest that you rather use an alternative essential oil or exercise caution when using this essential oil.
o Conflicting reports regarding Mugwort essential oil make it difficult to give a strong opinion.

Rue – Ruta graveolens

o We find that Rue essential oil is commonly listed in old references as being toxic. However, IFRA currently allows its use in perfumes and fragrances at a maximum dilution of 0.15% because Rue is photo-toxic.
o Rue is regarded to be an abortifacient, but it is reported that this occurs when the oil is ingested at high doses.
o High doses accelerate maternal toxicity and this is linked to the abortifacient effect of the essential oil.
o This oil should be avoided when pregnant or breastfeeding.

Thuja – Thuja occidentalis

o Thuja is used in herbal medicine and ‘thujone-free’ preparations are recommended. but as an oil it is a powerful abortifacient, poison, as well as a neurotoxin.
o The Thujone content is suspected to be the cause of toxicity.
o This essential oil can be applied to unbroken skin (dilution rate not to exceed 0.4%).