Essential Oil Safety + Toxicology

With essential oils becoming so popular nowadays, everyone assumes they are safe because they are all natural and derived from plants. This could not be further from the truth. Essential oils are safe when used correctly, but most are not aware of the correct way to use them. In this blog post we’ll be going over essential oil toxicology and safety.

Essential oils are the volatile constituents in plants. They are small, “oily” compounds that are actually non-lipids. They’re volatile, meaning they evaporate, which is why we can smell them. Most essential oils are mixtures of terpenoids- most are solely composed of monoterpenes, but sometimes a blend of sesquiterpenes or small hydrocarbons as well. When extracted, essential oils are extremely concentrated and potent and should be used with caution. You can do a lot more harm and cause adverse reactions with essential oils than you can while working with whole plant medicine. For example, drinking a tea or herbal infusion is much safer than dropping a few drops of essential oil into a drink (which should never, ever be done). This is because once extracted from the plant matrix, essential oils on their own are much more concentrated. 




When used externally, essential oils should always be diluted with a carrier oil to around 1-2% dilution. Extreme caution should be used while applying essential oils to infants, children, and elders. This is because in all of these age groups, their detoxification enzymes in the body are not functioning as efficiently as they would in an adult. This means over time, with consistent use of essential oils, the constituents may build up in their systems and cause toxicity. Essential oils generally should not be used on infants or children 6 months to 1 years old. There is a selection of essential oils that are safe for use on older children. Both elders and children should use essential oils with the lowest dilution rate possible, and should never ever be exposed to undiluted essential oils. Children are obviously in general much smaller than adults, making the dose of essential oils much higher. Elders should also approach essential oils with caution due to thinner skin. 

While using essential oils externally, make sure to store essential oils correctly to avoid oxidation. Essential oils are very delicate compounds and can oxidize easily. The different methods of extraction can lead to faster “breakdown” of the constituents, leading to oxidation. Breakdown can alter the essential oil terpenoids and potentially cause them to become skin irritants. Make sure to purchase your essential oils from a reputable supplier, use them within their best by date, and store them properly. Most essential oils benefit from being stored out of direct sunlight, in a dark, cool area, or even in the fridge. 

Essential oils that are potentially phototoxic should be used with caution as well. Furocoumarins (FCs) are one of the constituents in some essential oils that can cause phototoxicity or sensitivity. After using these essential oils in a carrier oil or a leave on product (any product you do not wash off the skin) the skin where the essential oil was applied should not be exposed to the UV rays in sunlight for 12-18 hours after. Furocoumarins are in most citrus essential oils and others such as angelica root and cumin. Some essential oils can be purchased furocoumarin free, with them removed. 


When it comes to essential oil safety, essential oils should only be used externally. I know I am going to ruffle a lot of feathers by saying that, but the truth is, essential oils should only be used internally under the care and guidance of a physician. I know, you’re probably wondering then why you’ve seen it recommended to add drops of EOs into water or tea. The truth is, the masses have been largely misguided on essential oils. For example, and this is NOT to condemn the individuals specifically, but most individuals working for MLM companies selling essential oils are not given any essential oil safety or toxicology training. A lot of these companies actually preach misinformation to their employees as well. The bottom line is, essential oils are far too concentrated to be used internally and should very rarely be ingested. 

To put it into perspective, 1-2 drops of essential oils are enough to overdo it when it comes to ingesting them. 1-2 drops of essential oils can be equal to a pint or more of dried herb matter, depending on the plant. Could you imagine drinking 28 cups of peppermint tea, consuming a whole pint of dried lavender, or eating multiple citrus peels all at once? Additionally, when you add essential oils into water, they sit only on the surface and the two liquids stay separate. Once you drink that water, the undiluted, extremely concentrated essential oils coat the esophagus and have the potential to leave a chemical burn. Not only is your esophagus at risk, but your liver is at risk as well. Think back to what I mentioned above- if you were to eat multiple orange peels, or drink 28 cups of peppermint tea, most likely your body would start to feel sick and nauseous right at the beginning of the experience. This is because your body is not equipped to handle such a large amount of these substances, and to protect itself, it will give you hints to stop consuming the tea, citrus peels, etc. While taking essential oils internally, you are overriding your body’s ability to let you know when enough is enough by consuming such a concentrated amount. Overtime, if you are consistently consuming essential oils, it is going to take a toll on your liver and kidneys, as the constituents build up and potentially result in nephrotoxicity. 

When it comes to taking essential oils internally, there are three of them that can actually be fatal. Pennyroyal, wintergreen, and eucalyptus, when ingested in milliliter quantities (1 mL = 30 drops) can cause fatal poisonings. Pennyroyal essential oil contains a high concentration of pulegone, a monocyclic monoterpene ketone that is hepatotoxic and neurotoxic when excess amounts are ingested. Historically, pennyroyal EO has been used to induce abortion, which is where most cases of fatal poisonings are sourced. Because of this, pennyroyal essential oil can be hard to purchase/find in the marketplace. Wintergreen essential oil contains up to 99% methyl salicylate which is not to be used during pregnancy, breastfeeding, or on young babies or children. There are multiple reports of fatalities in children and adults after ingesting wintergreen essential oil or being exposed dermally to high amounts of the essential oil. Eucalyptus essential oil is high in 1,8 cineole, also known as eucalyptol, with concentrations ranging from 47-95%. Eucalyptus is not as toxic as pennyroyal and wintergreen, but there have been reports of children experiencing serious toxicity from ingesting 5 mL of the essential oil, fatalities reported after children ingesting 15 to 30 mL, and fatalities from adults ingesting 25 mL. For this reason these essential oils should never be ingested, and correct dilution is required if these essential oils are going to be applied on the body. 

Instead of consuming essential oils internally, simply make a whole plant infusion with the herb (as long as they are safe for ingestion, that is). You will then be consuming multiple beneficial herbal constituents and a miniscule amount of (around .005%) essential oil which is more than enough. If you are consuming citrus essential oils for their high limonene content, try blending a small piece of orange or lemon peel into your morning smoothie. This will have the same benefit, but on a safe level. Alternatively, ingest lemon or orange peel by adding the zest to your food or add some of the peels into a homemade jam to get their high antioxidant content and anticancer benefits. There are multiple ways to work around using strictly essential oils and using whole plant medicine instead. 


Essential oils are widely used on pets as well. Extreme caution should be used while using essential oils on your animals. Dogs and cats do not contain the same liver enzymes as humans that are needed to detox these essential oils from their bodies. This can lead to a build up of essential oils in their bodies and could potentially be fatal. There are multiple sources that claim certain essential oils are safe for use on dogs, cats, and other pets, but essential oils have not even been clinically tested for use on humans, let alone animals. Before applying a product to your pet that contains essential oils, think about how it is possible that the animal could lick the product off, and therefore ingest the product. To be safe, do not use any products with essential oils on your pets. 

There have also been reports of animals dying from their owners diffusing essential oils in the home. Consistent diffusing of essential oils around animals is enough for the animal to react adversely to it. Essential oils are aromatic because the particles are small enough to pass through the blood brain barrier- inhaling excess amounts of an essential oil is enough to become neurotoxic to cats and dogs. To be safe, use essential oils away from pets or make sure the area is well ventilated. 

For more information on essential oil safety and toxicity, I highly recommend the book Essential Oil Safety: A Guide for Health Care Professionals, by Robert Tisserand and Rodney Young. 

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