toxic essential oils

23 Toxic Essential Oils That Offer Surprising Benefits

In my previous article I was talking about the dangers of essential oils. I was also talking about their toxicity and precautions. Certain toxic essential oils are limited or even prohibited to use on skin or taken orally.


But with the proper guidance and a good research you will find out that even toxic essential oils can be useful to your body and its well-being.


In this article I will detail 23 toxic essential oils that are found on many black lists. Some are either prohibited or banned by certain organizations. You should know about them because most of them have amazing medicinal and Aromatherapy properties. Plus, I believe that the essential oils safety is a must before handling any oil or blend.




If used in low doses even those toxic essential oils are not toxic anymore! Those low doses refer to skin applications between 2% – 2, 5% dilutions. If you swallow a large dose of essential oil without the consent of a doctor you can end up with some severe reactions.


Those reactions can go as far as inducing a coma or in some cases, even death.


What Makes Essential Oils Toxic?


An essential oil is a concentrated substance. One single drop contains the properties and chemical compounds from tens of plants. This makes a larger quantity of essential oil dangerous to your body.


For example: To make an ounce of Peppermint essential oil, there’s a need of around 16 pounds of fresh leaves of peppermint.


Some plants contain high levels of dangerous compounds. Here are the 23 essential oils considered dangerous, with their benefits and precautions:


Essential Oils that Belong to the Lauraceae Family


It’s a family with over 3000 flowering plant species. They are found mostly in tropical and temperate regions and the majority is made up by evergreen shrubs or trees. All plant species in this family are very rich in essential oils.


Cinnamon Bark Essential Oil


This oil is made from the bark and the leaves of the cinnamon tree. Pure Cinnamon Bark is a toxic essential oil and it is a lot more expensive than the usual Cinnamon essential oil.


Botanical name: Cinnamomum verum (bark) and Cinnamomum zeylanicum (leaves)

Constituents: Cinnamaldehyde, cinnamyl acetate, linalool, caryophyllene and cymene.

Uses: Constipation, flatulence, rheumatism, exhaustion, stress, sexual stimulant, increases blood circulation. It can also be used in baking or cooking.

Adverse reactions in high doses: Can cause allergies and it can affect the fetus (embryotoxicity). It can also cause sensitivity in mucous membranes. Do not inhale this oil! Also, do not ingest large doses of this oil! It’s among those few toxic essential oils that need special care when used. Only apply on the skin within the 2% dilution limit.

Precautions: Always dilute a maximum of 0.1% of the Cinnamon Bark essential oil. That means one single drop to 30 or 40 ml of carrier oil (2 or 3 tbsp). And don’t use it on kids younger than 6 years old. Do not use in excess to avoid skin sensitization.

Blends well with: citrus essential oils (Lemon, Grapefruit), Geranium, Cardamom, Rosemary and Lavender


Cassia Essential Oil


The Cassia essential oil is also known as Chinese Cinnamon. It’s extracted through steam distillation from the twigs and leaves of the tree.


Botanical name: Cinnamomum Cassia but also Cinnamomum Aromaticum or Laurus Cassia

Constituents: Cinnamic aldehyde, linalool, cinnamyl acetate, chavicol and benzaldehyde

Uses: Great anti-depressant, stops nausea and vomiting and it can stop diarrhea as well. It also has antimicrobial properties and it improves the blood circulation. The Cassia oil makes a good treatment in arthritis and rheumatism. Among many others, Cassia oil can increase the libido and improve sexual disorders (impotency etc.)

Adverse reactions in high doses: It can make the skin sensitive after a long use. And it can irritate the skin if used in high doses. You should protect your mucous membrane by not inhaling it directly – it’s a hot oil. Because it contains cinnamaldehyde, just like the Cinnamon Bark oil, you’ll have to also use a maximum of 1 drop per 30-40 ml of carrier oil.

Precautions: Dilute, dilute, dilute! And don’t take essential oils internally unless you’ve made your research or talked to a doctor.

Blends well with: Geranium, Nutmeg, Rosemary, Black Pepper, Chamomile, Ginger, Frankincense and Coriander


Camphor Essential Oil


The Camphor essential oil is extracted from the common Camphor tree through steam distillation.


Botanical name: Cinnamomum camphora

Constituents: camphor, borneol, pinene, terpene, safrol, camphene and alcohol

Uses: It disinfects everything. It can stimulate a lazy metabolism and a bad circulation. It can also eliminate gases and prevent bloating. On a local application, it causes numbness so it can act as an anesthetic. Being a blood stimulant, it can behave as an aphrodisiac when ingested. It’s a good sedative and it also has anti-inflammatory properties.

Adverse reactions in high doses: The Camphor oil is among the most toxic essential oils. Used in excess, it may cause a loss of control over your limbs and even death. 2 grams of Camphor essential oil might be fatal. Its smell is addictive too.

Precautions: Dilute it all the time and always use under 1 gram. And do a thorough research before using it for the first time.

Blends well with: Chamomile, Basil, Cajuput, Lavender and Melissa aromatherapy essential oils


Sassafras Essential Oil


This essential oil is obtained through steam distillation of the dried root barks of the plant.


Botanical name: Sassafras albidum

Constituents: High concentration of safrole, asarone, camphone, coniferaldehyde, thujone, and eugenol

Uses: Skin eruptions, gout, pain caused by rheumatism, menstruation and head lice.

Adverse reactions in high doses: Safrole is among those toxic essential oils with carcinogenic effects (can cause cancer). It can be lethal if the correct dose is not used. This is a case where you should look for a doctor to explain to you how to use Sassafras essential oil. Also, Sassafras has narcotic effects being the precursor of ecstasy drugs.

Precautions: Used with extra caution and in the lowest dose possible. Consult a doctor before using it or do your research when considering the use of Sassafras.

Blends well with: The Sassafras essential oil is not among the approved aromatherapy essential oils. Since it’s been banned by the FDA there are no known interactions with other oils.


Toxic Essential Oils with Narcotic Effects


Narcotic substances derived from the following plants can affect the behavior of a person. They can alter the mood and they can create addiction as well. Great caution is advised when handling or using these essential oils.


Tansy Essential Oil


All the plant parts of tansy are steam distilled for the extraction of the essential oil.


Botanical name: Tanacetum vulgare, Tanacetum annuum

Constituents: borneol, artemisone, camphor, camphone, piperitone, thujone and artemisone and isopinocamphone

Uses: Kills any bacteria and fungus in the human and animal body. Relieves the skin inflammation and controls all allergic reactions. It’s a good sedative (calms hysteria attacks, convulsions, anxiety, anger etc.)

Adverse reactions in high doses: It can make you have hallucinations and cause severe nervous discomfort. It has narcotic effects and can be addictive, which makes it one of the most dangerous essential oils.

Precautions: It’s highly poisonous and it should always be used diluted in a carrier oil to neutralize some of its effects. Use the smallest dose possible and do your research before taking Tansy.

Blends well with: Rosemary, Lavender, Helichrysum, Ravensara and Cedarwood


Wormwood Essential Oil


This toxic essential oil is obtained through steam distillation from leaves, twigs and flowers of the wormwood plant.


Botanical name: Artemisia absinthium

Constituents: geranyl propionate, myrcene, sabinene, high concentration of alpha and beta thujone, trans sabinyl acetate and trans sabinol

Uses: It generally stimulates all kinds of discharges (bile into the stomach) making the digestion easier. It can be used as a deodorant (with a low dose) and can treat obstructed menstruations that can lead to uterine tumors. It also helps diminishing the period symptoms. It tones up the whole body and its systems (circulation, digestive etc.)

Adverse reactions in high doses: It has narcotic effects and it’s addictive and poisonous because of the neurotoxin thujone. It can cause severe convulsions, rash behavior and ultimately death. Wormwood is a part of the toxic essential oils group. A prolonged use is capable of damaging the brain permanently.

Precautions: You are not allowed to use it for medicinal purposes for a long time. Always dilute it!

Blends well with: Lavender, Orange, Oak Moss and Jasmine aromatherapy essential oils


Calamus Essential Oil


Another toxic essential oil, Calamus oil is made from the roots of the plant (dried or fresh) by steam distillation.


Botanical name: Acorus Calamus

Constituents: camphone, calamusenone, iso shyobunine, calamendiol, beta asarone, shyobunone, acorenone, beta gurjunene, alpha calacorene and alpha aslinene

Uses: Stimulates the blood circulation and the nerves. Relieves the pain caused by rheumatism and arthritis. It’s a natural antibiotic and fights infections. In low doses, it can have a refreshing effect on the brain. It can also induce sleep because it has tranquilizing effects.

Adverse reactions in high doses: Asarone causes cancer which makes the Calamus essential oil part of those dangerous essential oils. It can cause hallucinations or severe convulsions and it has narcotic effects. A prolonged use of Calamus oil may cause tumors.

Precautions: Always use the smallest dose and ask for an doctor’s advice. Or do a lot of research if you want to use Calamus essential oil.

Blends well with: Cinnamon and Lavender. Also Clary Sage, Cedar Wood and Marjoram but goes well with Oregano, Ylang Ylang, Patchouli and Tea Tree as well


Boldo Essential Oil


The leaves of the Boldo plant are steam distilled to get this toxic essential oil.


Botanical name: Peumus boldus

Constituents: ascaridole, limonene, cineole, linalool, alpha and beta pinene and camphene

Uses: Great sedative for the stomach issues. Reduces inflammation caused by excessive use of drugs, spicy food, etc. It helps relieving stomach acidity. Because it’s a stimulant (narcotic effects) it can relieve all pain related to arthritis and rheumatism. It’s a good antimicrobial and fights infections, including those of the liver, protecting it.

Adverse reactions in high doses: Ascaridole is considered toxic and it can have severe consequences (convulsions and coma). Nausea and headaches may occur because of the plant’s intoxicating effects.

Precautions: Boldo essential oil is another member of the toxic essential oils. So when it comes to ingesting it, make sure you know exactly what you’re doing. Look for the advice of a doctor first. Keep in mind that this oil is highly toxic.

Blends well with: The Boldo essential oil has no use in Aromatherapy because of its smell.


Rue Essential Oil


Obtained through steam distillation, Rue essential oil is extracted from the fresh rue plant.


Botanical name: Ruta graveolens

Constituents: Nonanone, bergaptene, butanone, xanthotoxin, psoralen, undecanone

Uses: Kills bacteria and viruses and relieves the pain caused by rheumatism or arthritis. It is effective in killing insects too. It can work very well in treating neurotoxins but not hemotoxins. This makes it a good poison counter (from snakes, narcotics intoxications or stings). It’s also a nervous sedative (anti-epileptic).

Adverse reactions in high doses: This dangerous essential oil can irritate the skin and cause abortions. It can also cause sun sensitization.

Precautions: Rue is on all toxic essential oils lists. It is poisonous, so avoid direct inhalations or touching the sensitive areas like ears or eyes. Don’t use this essential oil undiluted.

Blends well with: Fennel, Thyme, Pennyroyal, Myrrh, Chamomile aromatherapy essential oils


Mugwort Essential Oil


This toxic essential oil is extracted through steam distillation from the flowers, buds and leaves of the mugwort tree.


Botanical name: Artemisia vulgaris

Constituents: Alpha and beta thujone, camphone and camphene and cineole

Uses: Calms down hysteria and epileptic episodes. It can regulate the menstruation as well. It can also help with digestive problems and increases urination, making it a great diuretic. Calms down the nerves and stimulates most body functions. Maintains the health of the uterus and improves the memory.

Adverse reactions in high doses: Mugwort is one of the toxic essential oils that can cause abortion. It also causes irritations to all sensitive membranes and cavities. It’s poisonous and has narcotic effects on the brain.

Precautions: It should always be used in a low dose, always diluted and avoided by pregnant women.

Blends well with: Patchouli, Oak Moss, Cedar Wood, Pine, Sage, Rosemary


Dangerous Essential Oils from Plants that Can Be Used as Spices Too


The following plants have their use in the kitchen as well. They can give food a special taste and enhance its aroma besides having medicinal benefits.


Oregano Essential Oil


It is obtained from fresh leaves through distillation.


Botanical name: Oreganum vulgare

Constituents: A large amount of carvacrol. It also contains thymol, bisabolene, linalool, cymene, caryophyllene, borneol, pinene, geranyl acetate, terpinene and linalyl acetate.

Uses: It is a great anti-inflammatory oil and it can help with respiratory conditions. It’s antifungal, antibacterial and antiviral. It can also regulate menstruation and delaying the beginning of menopause. Allergenic and digestive, it is a lot gentler than all the available drugs.

Adverse reactions in high doses: Oregano essential oil may cause irritation to the mucous membrane, and the skin. It can also cause miscarriage because of its power to regulate the hormones’ activity. It is a dangerous essential oil because it can damage the vaginal flora. That may happen especially when it’s taken internally in a high dose, for a long time. It may also cause allergic reactions.

Blends well with: Rosemary, Bergamot, Lavender, Cypress, Chamomile, Tea Tree, Eucalyptus and Cedar Wood


Clove Essential Oil


This essential oil is extracted from the dried buds of the clove.


Botanical name: Eugenia caryophyllata

Constituents: Eugenol, carvacrol, thymol, methyleugenol, caryophyllene, eugenyl acetate, isoeugenol

Uses: Clove essential oil fights infections and bacteria or viruses (like hepatitis C). It also boosts the immune system and fights acne. It is great in dental care (mouthwash, toothpaste, sore gums etc.). It’s a natural aphrodisiac. And also fights stress, indigestions and ear aches among so many others.

Adverse reactions in high doses: Being on the list of toxic essential oils, Clove can cause kidney and liver failure and stomach discomfort in kids. It can cause a drop in the blood sugar (diabetics beware!). It has not yet been confirmed if Clove essential oil affects the mother’s milk so consult a doctor before using it.

Precautions: It’s a strong essential oil so you should not use more than a 0.5% dilution of Clove oil. Always start with small amounts of oils that you’re not used to.


Cumin Essential Oil


Cumin essential oil is extracted through steam distillation after crushing its seeds. It’s considered a toxic essential oil with volatile properties (it evaporates into the air).


Botanical name: Cuminum Cyminum

Constituents: cymene, pinene, cuminic acid, limonene, dipentene and phellandrene

Uses: Is able to cure and fight all infections in the intestines. But also skin infections, ears and wounds. Gets you rid of gases. Cumin reduces the blood pressure and makes you urinate more frequently. We lose around 4% of fat through urine so it’s efficient in weight loss as well. Detoxifies and calms down the nerves. It is also a great body tonic.

Adverse reactions in high doses: Vomiting may occur and it can cause sun sensitization. Its smell may cause nausea or even headaches.

Precautions: Use only small doses and always dilute it. Also, remove all essential oil safety concerns by talking to a doctor first.

Blends well with: Coriander, Chamomile, Angelica and Caraway essential oils.


Horseradish Essential Oil


The Horseradish essential oil is made from the roots of the plant through steam distillation.


Botanical name: Armoracia rusticana

Constituents: Mustard oil and its glycosides, asparagine, resin, peroxidase enzymes and ascorbic acid

Uses: It is antibacterial and can treat urinary infections. But it can also treat inflammations of sinuses, joints, edema and tissues. It can kill the intestinal worms and relieve sciatica pain.

Adverse reactions in high doses: Being one of the toxic essential oils it can cause diarrhea and blood vomiting. It can also cause inflammation and can be caustic when ingested. Rashes and allergic reactions can occur also. It can irritate the nose membrane when inhaled.

Precautions: It is generally considered a safe root. So it’s used in the kitchen for flavoring and seasoning. But consumed in high doses it’s highly toxic. Always dilute your Horseradish essential oil. And consult a specialist if you are not sure about the right dose for ingestion.


Plants with High Antibacterial, Antifungal and Anti-Inflammatory Properties


The following toxic essential oils are great at killing all bacteria and fungi in people and in animals. These herbs use toxic substances as a natural defense mechanism.


Ajowan Essential Oil (aka Bishop’s Weed)


It’s a toxic essential oil extracted from the fruit pods of the Ajowan (Ajwain) plant (related to parsley). It smells like Oregano.


Botanical name: Trachyspermum Ammi

Constituents: High in thymol (30 – 50%), limonene, gamma-terpinene, p-cymene and alpha-pinene.

Uses: Antimicrobial and antioxidant. It treats sinus congestion and stimulates the appetite. It also improves (and warms) the blood circulation and helps with sleep. It refreshes the breath and deals with constipation and indigestion.

Adverse reactions in high doses: It can irritate the skin and the mucous membrane.

Precautions: Always dilute the Ajowan essential oil and do a patch test to see if you’re allergic. Go with small doses at first. 1 drop in a tablespoon of carrier oil for a skin massage should give you an idea how well it works for you. Also talk to a doctor if you have concerns or doubts.


Mountain Savory Essential Oil (or Wintergreen)


It’s extracted through steam distillation from the leaves and flowers of the plant.


Botanical name: Satureja Montana

Constituents: high in phenols, carvacrol (30 – 40%), thymol (20 – 30%), cineol, pinene and cymene.

Uses: Boosts the immune system and the circulatory and nervous systems. Good antiseptic (treats bites, burns etc.) and it’s a great body tonic too! It can also treat that excessive thirst that diabetic people experience. The summer savory (Satureja hortensis) is well recognized and used in the kitchen.

Adverse reactions in high doses: In a lab experiment, half of the hairless rat population died. They died when they were massaged with undiluted Savory essential oil. But this toxicity has not been found harmful to the human skin.

Precautions: Do not use Savory essential oil undiluted! And always use small doses to benefit from its properties.

Blends well with: Pine Needle, Peppermint, Lavender, Rosemary, Spearmint and citrus oils


Pennyroyal Essential Oil


This dangerous essential oil is obtained through steam distillation from the fresh pennyroyal herb.


Botanical name: Mentha pulegium

Constituents: menthone, isomenthone and neomenthone and high in pulegone (which is a highly toxic and poisonous compound)

Uses: Works well against hysteria attacks. It’s antibacterial and antimicrobial. Treats rheumatic and arthritic symptoms and it can purify the blood too. It regulates the menstruation and eases up the digestion. Because of the pulegone substance, usually no virus can stand in its way, especially those found in the lungs.

Adverse reactions in high doses: Pennyroyal occupies the highest place on the toxic essential oils list. It can cause abortion but also death if used for a long time, in high doses. A death case in a pregnant woman showed that she had ingested around 28 grams (1 ounce) of Pennyroyal essential oil. It can damage the liver, lungs and the respiratory tracts through inhalation.

Precautions: never use more than the dose recommended by a doctor. This is usually low on skin massages (2% dilution). That way you can avoid experiencing the dangers of this plant. But always dilute and better talk to a specialist if you’re not sure.

Blends well with: Sage, Citronella, Rosemary, Geranium and Lavandin


Wormseed Essential Oil


It is extracted through steam distillation from the whole plant.


Botanical name: Teloxys ambrosioides, chenopodium ambrosioides

Constituents: ascaridole, methyl salicylate, cymene, myrcene, terpinene and limonene.

Uses: It is great in fighting intestinal parasites and it can also relieve menstrual related problems (like cramps). It is also useful in treating the fever with its antibacterial properties. It can stimulate the circulation for a better heart function and protects against various fungus types.

Adverse reactions in high doses: As a toxic essential oil, Wormseed can cause nausea, vomiting, visual problems, vertigo and deafness. The ascaridole can explode in contact with heat or organic acids because of its unstable nature. Wormseed essential oil can affect the nervous system and may cause paralysis.

Precautions: Toxic in large doses. A professional’s advice is always required when using Wormseed essential oil.


Wintergreen Essential Oil


Another member of the toxic essential oils list, Wintergreen oil is extracted from the leaves of the shrub through the steam distillation method.


Botanical name: Gaultheria procumbens

Constituents: methyl salicylate, gaultherilene

Uses: It acts like a natural anesthetic by numbing the massaged areas. It’s known to fight arthritic and rheumatic pain and relax the aching areas. It’s effective against stress and pain. It can cure sepsis and the infamous Staphylococcus Aureus. It works well to clear the obstructed menstruation and all its related symptoms.

Adverse reactions in high doses: Wintergreen is a highly poisonous essential oil, and it can be deadly to humans, animals. It can kill all sorts of bacteria and fungi when used in high doses too.

Precautions: Not to use on a frequent basis! And not to ingest! Only use in skin applications and in minimal doses!

Blends well with essential oils like: Vanilla, Oregano and Mint, and also with Thyme.


Arnica Essential Oil


The essential oil is extracted through steam distillation from the roots and flowers of the arnica plant.


Botanical name: Arnica Montana

Constituents: thymol, phlorol isobutyrate, linolenic and linoleic acids and myristic and palmitic acids as well.

Uses: It can relieve pain and swelling and it can treat a wide range of infections too. It’s a great hair tonic and fights dandruff effectively. Arnica essential oil relieves from muscle spasms and aches, and rheumatic or osteoarthritis pain. And it’s good in treating any type of swelling or sprains and bruises.

Adverse reactions in high doses: It may increase the heartbeats and can cause nervous discomfort. Tremors or dizziness are also among the side effects of using Arnica oil. Vomiting, dizziness and irritation of the mucous membrane and stomach may also occur.

Precautions: Don’t apply Arnica essential oil directly on open wounds! Don’t ingest it unless you’ve done your research or talked to a specialist first. Always use low doses!


Mustard Essential Oil


Mustard essential oil is extracted from grinded seeds of the mustard plant. It is then mixed with water. After the steam distillation it results a volatile toxic essential oil.


Botanical name: Brassica nigra (black mustard) or brassica hirta (the white mustard)

Constituents: Myrosinase and sinigrin (characteristic compound of mustard). They form allyl isothiocynate and simple isothiocynate that give this oil its toxic properties. We can also find erucic, oleic and linoleic acids that have health benefits.

Uses: Stimulates the digestion and blood circulation. It’s also a great antibacterial and antifungal. Revitalizes the hair, tones up the body and releases the toxins through sweat and pore enlargement. It can also help with colds and flus. Promotes dental and gum health as well.

Adverse reactions in high doses: being among the dangerous essential oils, Mustard oil can irritate the sensitive membrane of the nose. But other than that, all India’s population has used it for centuries and still does without any significant side effects. But only when used in small doses because it has toxic constituents.

Precautions: Use with caution and measure, do your research and always dilute Mustard essential oil.


Savin Essential Oil


This essential oil is extracted from the shoots, leaves and twigs of the Juniper shrub through steam distillation.


Botanical name: Juniperus Sabina (prohibited by IFRA) is NOT the same as Juniperus Phoenicia (not prohibited)

Constituents: Tannins and resins

Uses: Mixed with honey can remove freckles. It’s effective against baldness, helps the womb to decongest, and relieves rheumatic pains.

Precautions: It’s usually used as a tincture. But you should seek a doctor’s help to see the right dosage and for how long you need to take it.


Oak Moss Essential Oil


The first extraction method is through solvent extraction. And then it’s continued with the vacuum distillation method from the moss of oak trees.


Botanical name: Evernia prunastri

Constituents: Delta usnic and evernic acid, atranorine, chloratronorine

Uses: Protects against sepsis and soothes all irritations or inflammations. It improves breathing issues and coughs or asthma. It can also protect against external factors that cause premature aging. It speeds up the body’s healing process as well.

Adverse reactions in high doses: Causes irritation on sensitive body areas (nose, eyes, ears, etc.)

Precautions: It’s not indicated for people suffering from hysteria or epilepsy attacks.

Blends well with: Geranium, Patchouli, Neroli and Lavender essential oils


Now that you know about the dangers of toxic essential oils, but also their benefits, would you use them to treat those health problems that give you a hard time?


The toxic compounds of these essential oils make them useful, even in modern medicine. And in low doses they can certainly help people treat some of their health problems.


Can essential oils be dangerous? Yes they can, but only if the right dose is not respected. So use them with extra care and attention and they’ll be your best friend in many life situations.


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