Toxic 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 that should not be used on the body in massage therapy nor ever ingested because of their high oral and dermal toxicity.

Please note that any essential oil should not be taken internally, excepts when so prescribed by a qualified and licensed medical practitioner.

Underneath 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
    • Prussic acid – also known as cyanide, is the main constituent of bitter almond oil, and even small amounts can be lethal.
    • Almond essence is made from this oil, but only after the prussic oil has been removed with rectification and washed by alkali, but is now replaced by synthetic flavoring.
  • Boldo – Peumus boldus
    • The dried leaves are used in herbal medicine, but the oil is powerful and even in very small quantities produces convulsions.
  • Camphor – Cinnamomum camphora
    • Although camphor is used in the treatment of certain infectious and respiratory diseases, oral ingestion is toxic.
  • Cassia – Cinnamomum cassia
    • This herb is used for a series of digestive complaints, yet is a dermal sensitizer and also irritates the mucus membranes.
  • Horseradish – Cochlearia armoracia
    • The herbal use of horseradish is apparently effective to treat coughs, yet the oil of horseradish contains allyl isothiocyanate (as does mustard oil) and is an irritant to the skin, eyes, nose and mucus membranes.
  • Mugwort – Artemisia vulgaris
    • Although this herb has been used for a variety of problems, the oil is toxic, an abortifacient and a neurotoxin.
  • Mustard – Brassica nigra
    • Although mustard seeds and powder do not contain allyl isothiocyanate, it is formed when the seeds come into contact with water and the essential oil is formed when a glycoside decomposes due to enzymatic action.
    • This oil is not only toxic because of its high content (92% minimum) of allyl isothiocyanate, but is also a skin and mucus membrane irritant.
  • Pennyroyal – Mentha pulegium
    • Although this herb has had a long use for various complaints including menstrual problems and as a stimulant, the oil is toxic and an abortifacient and can even in small quantities cause acute liver and lung damage.
  • Rue – Ruta graveolens
    • Although the herbal use of rue may be helpful, this oil will not only irritate and burn your skin when you apply it, but is toxic, an abortifacient, an irritant to the mucus membranes, a neurotoxin and cause sun sensitivity due to phototoxicity.
  • Sassafras – Sassafras albidum
    • This herb has been used for rheumatic pains and gout, but the oil is high in safrole (80 – 90%) which is banned by the FDA since it is carcinogenic (cancer causing) and it can be lethally toxic as well – even in small amounts.
  • Savin – Juniperus sabina
    • This oil is toxic since its content of sabinene, sabinol as well as sabinyl acetate, and is furthermore a skin irritant and an abortifacient.
  • Tansy – Tanacetum vulgare
    • Tansy oil is high in thujone, which is poisonous and also causes convulsions, vomiting, uterine bleeding etc and death is normally the result of respiratory arrest and organ failure.
  • Thuja – Thuja occidentalis
    • Even a herbal infusion of this can have medical complications, but as an oil it is a powerful abortifacient, poison as well as neurotoxin.
  • Wintergreen – Gaultheria procumbens
    • The active ingredient in wintergreen oil is methyl salicylate (98%) and although it has been used in ointments for rheumatism and other such complaints, the topical application of this oil, even in much diluted blends, can be a skin irritant – especially to those sensitive to aspirin (salicylate). Wintergreen oil is also very poisonous.
  • Wormseed – Chenopodium ambrosioides
    • The name is linked to the fact that wormseed was used to expel round and hookworms, but due to it toxicity to the liver and kidneys, and suppression of heart function, and general toxicity and neurotoxicity it is no longer used.
  • Wormwood – Artemisio absinthium
    • The drink absinthe (the drink of choice of Vincent van Gogh) contained wormwood and continuous consumption produces auditory and visual hallucinations, addiction and a couple of other unpleasant side effects.
    • The active ingredient is thujone, which is a convulsant and neurotoxin and the oil also has abortifacient properties.


See also Safety with Essential Oils