What Are Essential Oils?

The Merriam-Webster Dictionary defines “essential oil” as, “any of a class of volatile oils that give plants their characteristic odors and are used especially in perfumes or flavorings, and for aromatherapy”.¹

In their pure, most concentrated form, these oils are potent.

According to the Tisserand Institute, the oils you get in a bottle are 50-100 times more powerful than the oils in the plants themselves. ²

longhaired cat looking out a window - essential oils for cats

Essential oils have become popular with people as aromatherapy for various medical conditions both by diffusing into the air and applying to the skin.

There are also some veterinary applications for essential oils (Veterinary Aromatic Medicine).³

Perfume, air freshener, “natural” flea treatments, and many other products have oils as active ingredients.

Essential Oils Can Be Beneficial or Deadly

vet office - vet looking at records; essential oil toxicity

Drugs and essential oils are similar because both can have great benefits in proper dosages, but both can be deadly when improperly used and abused.

“Essential oils need to be regarded similarly to how we use drugs. There are species considerations, dosing considerations, and interval considerations.”⁴

Dr. Jeff Wilcke wrote something interesting in light of the evidence about essential oils… “Even drugs known for toxicity in cats can be used safely if we are aware of and compensate for certain peculiarities.”⁵

Claims About Essential Oils

tabby cat lying on a rug - are essential oils safe for cats?

People have made various claims about essential oils. Here are a few…

Cats are deficient in a liver enzyme that makes them unable to process (metabolize) certain chemicals in oils, causing the oils to build up and kill the cat

Phenols are toxic to cats

Citrus oils contain d-limonene and linalool that cause liver damage or failure

Cats are sensitive to compounds containing benzene rings

Pinene and terpineol are toxic to cats

Benzyl alcohol is toxic to cats

Eucalyptus oil and eucalyptol (1,8-cineole) are toxic to cats

Mint (especially peppermint) is toxic to cats

2 orange tabby kittens sleeping together; are oils toxic to kittens?

Tea Tree oil (Melaleuca alternifolia) is toxic to cats

Camphor is toxic to cats

Methyl Salicylate in birch and wintergreen is toxic to cats

Certain oils exist that are toxic to humans or animals

Are These Claims True?

scruffy older cat - are oils ok for older cats?

I searched and searched for scientific studies, anything to back up these claims, but found only a few studies and resources.

There are two sources that have scientific references, Tisserand Institute and Melissa Shelton, DVM.

Both advise you to treat essential oils the same way you do drugs… carefully and with the guidance of a knowledgeable veterinarian.

Tisserand Institute

Robert Tisserand and Rodney Young have written a helpful reference book, “Essential Oil Safety“, reviewing 400 oils.

If you want to know more about these oils, this book is worth exploring.

Melissa Shelton, DVM

White & black longhaired cat sitting on patio chair

The other is Melissa Shelton, DVM, a holistic veterinarian whose interesting article, “The Science Behind Cats and Essential Oils“, talks about what essential oils are and how they affect your feline friend.⁶

Using her veterinary skills and experience, Dr. Shelton has developed a line of high-quality essential oils that are safe for cats.

Find out more at AnímálEO (I make no money from these).

Dr. Shelton’s explanation of the studies and many scientific sources she lists is quite eye-opening and worth reading for anyone interested.

Claim #1 – Liver Enzyme Deficiency

Cats are able to metabolize essential oils but have a different elimination time than other animals.

A study mentioned by Dr. Shelton was about plasma half-lives for sodium salicylate.

“…it was discovered that ponies, swine, goats, dogs, and cats had drastically different elimination times… a cat actually took almost 38 hours to eliminate the drug, while a dog took just under 9.”⁷(emphasis added)

In plain English, your kitty’s body, especially the liver, processes chemicals in its own unique way.

It takes longer for it to get rid of the bad stuff than other animals.

The longer toxic things stay in the body, the more dangerous they are.

So don’t assume that what is safe for you or your dog will be fine for your cat!

Claim #2 – Phenols

What are Phenols?

“In organic chemistry, phenols are a class of chemical compounds consisting of a hydroxyl group (—OH) bonded directly to an aromatic hydrocarbon group.”⁸

Grapes, garlic and onions are a few of the fruits and vegetables that contain phenols.

The claim that phenols are toxic is based on a very old study and has NOTHING TO DO WITH ESSENTIAL OILS.

The study is about “benzyl alcohol being injected, added to meat products as a preservative, or used as a bacteriostatic in drug or biological products…⁹

Even though cats have problems metabolizing phenols, they are able to do so.

They don’t build up over time, just take longer to eliminate from the body.

Phenols are a good example of compounds that are helpful in very diluted forms and deadly in higher doses.

Many Uses of Phenols

white cat watching something intently - litter

Check out Wikipedia for lots of information about the many uses of phenols, in medicine, insecticides, plastics, etc.¹⁰

“…if you only read the headline of ‘Toxicosis in cats from the use of benzyl alcohol in lactated Ringer’s solution’ in the Journal of American Veterinary Medical Association in 1983, you may worry also about the use of any phenol…

onions, garlic & shallot - can be used as oils and medicines

If you knew nothing of veterinary medicine, feline physiology, or the vast difference between a chemical benzene ring and a natural substance containing a benzene ring, you would err on the side of caution.”¹¹

Dr. Shelton mentions a 2011 article about feline kidney disease that she says indicates…

“…there are alternative methods for phenol metabolism, than simply the liver enzyme pathways that cats possess.

With logical and appropriate use of essential oils containing natural phenol compounds, cats clearly compensate for any reduction in metabolism speed.

It again, is all dependent on the dose and frequency of administration.”¹²[emphasis added]

The conclusion to all this fancy talk is that cats are able to handle phenols in lower doses and in regulated frequency.

They should be used under the guidance of a knowledgeable veterinarian.

Claim #3a – Citrus Oils: d-Limonene

What is d-Limonene?

d-Limonene is a colorless liquid aliphatic hydrocarbon… a major component in oils of citrus fruit peels¹³

Lemons, limes, grapefruit, oranges, and other citrus fruits contain d-Limonene.

It’s used as a flavoring agent in manufacturing foods.

There’s not much information available about possible d-limonene poisoning of cats.

Dosage Amount is Key

While following the trail on this subject, I found info that shows the same conclusion as phenols.

There’s no problem at low dose levels, but once you make the concentrations higher, you’re in trouble… and you won’t be doing that with your precious kitty, will you?

Evidence of the Dosage Problem

Dr Shelton quotes an article in the Journal of the American Veterinary Medical Association¹⁴ that describes the effects on cats of a commercial insecticidal dip containing d-limonene.

Using the manufacturer’s recommended concentration (1.5 oz per gallon of water), they found no sign of any problem. [emphasis added]

As they increased the concentration, reactions such as drooling and shaking muscle tremors happened.

These and other problems began at 5 times the recommended concentration and worsened as the concentration got stronger.¹⁵[emphasis added]

“Symptoms of limonene toxicity may include hypothermia, tremors [shaking], ataxia [uncoordinated muscles] and excess salivation.

Agitation and vocalization may also occur.

Irritation of the skin, particularly around the scrotum, has been reported and ocular irritation may occur if eyes are accidentally exposed.”¹⁶

Always read the label’s “Precautionary Statements” to read about the potential for skin irritation and sensitivity of some animals to treatment (e.g., kittens, seniors, and cats with liver or kidney diseases).

You’ll probably also notice they caution you against using their product undiluted if it’s in concentrated form.

Claim # 3b – Citrus Oils: Linalool

What is Linalool?

The Merriam-Webster Dictionary defines “linalool” as “a fragrant liquid alcohol C₁₀H₁₈O that occurs both free and in the form of esters in many essential oils and is used in perfumes, soaps, and flavoring materials”.¹⁷

In a 2002 article “Caveat Emptor: Safety Considerations for Natural Products Used in Arthropod Control“, John T. Trumble talks about linalool primarily in dips and sprays.

His research found nothing indicating linalool causing reactions in cats or other animals.¹⁸

Testing was done on the effectiveness of linalool against fleas on live cats and the following was reported in an article called “Controlling Ticks and Fleas with Linalool“…

“Infested cats were ‘dipped’ in one of the following linalool compositions: 1.0%, 0.5%, and 0.5% +MGK-264 synergist.

This synergist was used because both it and piperonyl butoxide prevented recovery of immobilized fleas and increased the toxicity of linalool.

Cats dipped in linalool exhibited no ill effects. [emphasis added]

The 1.0% dip and the 0.5% dip with synergist were both 100% effective as all fleas were eliminated from 3 treated animals.

The residual activity of linalool was evaluated by re-infesting a flea-free cat 8 days after treating it with 1.0% linalool. No residual activity was observed.”¹⁹

Claims #4 – Benzene Rings and #5 – Benzyl Alcohol

What are Benzene Rings?

Ball-and-stick model of a benzyne ring — Ball and stick model of a benzyne ring

According to Wikipedia, benzene “is an organic chemical compound with the molecular formula C₆H₆.

The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each.

It’s classed as an aromatic hydrocarbon.

Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma around petrol (gasoline) stations.”²⁰

What is Benzyl Alcohol?

Benzyl alcohol is a mildly aromatic colorless liquid. It’s often used as a treatment to kill lice on people.

Dr. Shelton has this to say about benzene rings and benzyl alcohol…

“These are also often listed as toxic to cats, and often are linked with phenol toxicity explanations.

The main research that supports this claim is from 1982, when the FDA issued a statement finally claiming Benzyl alcohol hazardous as a parenteral preservative.

While this substance is related to other chemicals found within essential oils, it is noteworthy that this is a synthetic compound, which was being used as a preservative in intravenous fluids.

A much different situation than the proper use within aromatherapy applications. (emphasis added)

Benzyl alcohol is mainly found in ‘essential oils’ that are not recommended for use with animals – these include Benzoin and other absolutes such as hyacinth, narcissus, violet leaf, champaca, bakul, and jasmine.”

Claim #6 – Pinene & Terpineol

Pine, fir, cypress, cedar, juniper, and spruce are in the “pine-type” family of oils. They contain pinene and terpineol.

What is Pinene?

Pinene is an alkene hydrocarbon that’s in over 400 essential oils.

Dr. Shelton notes there is a report on Pine-sol® toxicity from 1986 about oils containing a-pinene oxidizing and causing “…increased rates of sensitization and reaction”. The oxidation is the problem not pinene itself. (emphasis added)

Her conclusion: “…we should be careful to use fresh, non-damaged essential oils, and use them with proper dilutions and protocols, [emphasis added] [but] there did not appear to be an overt reason to avoid the chemical pinene in cast specifically.” ²¹

What is Terpineol?

Terpineol is “a group of four monoterpene alcohol isomers. The most common form of terpineol is alpha-terpineol (a-terpineol).

Terpineol occurs naturally in more than 150 plants, including cannabis, lilacs, lime blossoms, eucalyptus sap and pine trees.”²²

Terpineol is an ingredient in many essential oils and is claimed to be harmful.

I could not find any sources showing evidence of problems being caused exclusively by terpineol.

Cajupet is an oil that contains terpineol and is high in 1,8-cineole.

Most likely, it’s like many others… safe for your buddy when properly diluted, but potentially harmful in higher dosages.

Use it only as directed by a knowledgeable vet.

Claim #7 – Eucalyptus Oil and eucalyptol (1,8-cineole)

Eucalyptus oil is often on lists of toxins for cats. So far, my sleuthing has found no sources to back this up.

The lists also don’t give any information on what varieties of eucalyptus they consider to be dangerous.

Eucalyptol (1,8-cineole) is in eucalyptus, “…camphor, laurel, bay leaves, tea tree, wormwood, rosemary, common sage, Cannabis sativa,”²³, and cajuput, among other plants.

The information available shows that low doses are okay, but anything higher than the recommended dosage can cause problems.

That’s when the problems start, so just be careful when using these oils.

In a clinical microbiology review by C.F. Carson, K.A. Hammer, and T.V. Riley, “Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties“, Jan. 2006, they state…

“For many years cineole [eucalyptol] was erroneously considered to be a skin and mucous membrane irritant, fuelling [sic] efforts to minimize its level in TTO

This reputation was based on historical anecdotal evidence and uncorroborated statements… and repetition of this suggestion appears to have consolidated the myth. Recent data, as discussed later in this review, do not indicate that 1,8-cineole [eucalyptol] is an irritant.”²⁴

According to Dr. Shelton, “Research even indicates it being protective against hepatotoxicity [liver damage caused by drugs] (2014, Eucalyptus globulus extract protects upon acetaminophen-induced kidney damages in male rats.)

Research would appear to support that while topical and oral administrations of this oil should be done with care, diffusion is likely to hold no harm.”²⁵[emphasis added]

Claim #8 – Peppermint (Mint Family)

Mints, especially peppermint, show up frequently on various toxic lists, but there are no sources or evidence on these lists to justify this.

According to Dr. Shelton, any problems with oils containing mint are from misuse and overdosing by full undiluted oil being swallowed or put on the cat’s skin.²⁶[emphasis added]

Claim #9 – Tea Tree (Ti Tree) (Melaleuca alternifolia)

What is Tea Tree?

Melaleuca Alternifolia is a small tree in the Myrtle family (Myrtaceae) that’s native to Australia.

Tea Tree is on many lists as one of the main oils to avoid with cats, sometimes listed with exclamation marks!

Is this alarm justified? Do you need to fear for your little buddy’s life?

According to a 1998 study of three cats poisoned with tea tree oil,²⁷ the cats were given a HIGH DOSE as a flea dip directly on the skin.

“The cats were severely infested with fleas, so they were shaved.

The shaving produced no nicks on the skin; however, numerous flea bites were visible.

The product used to eliminate fleas was labeled for use as a spot treatment for skin lesions, but a catalog advertised that it would repel fleas when diluted and used as a dip.

The product contained 100% oil of Melaleuca alternifolia.

The oil was applied directly to the cats’ skin, and 2 1-oz (approximately 60 ml) bottles were used on the 3 cats.”

Product Misuse

Tea tree oil toxicosis reported in dogs and cats is associated with misuse of the product, as was the case in this report.

The cat that died in this case, cat 2, had central nervous system depression typical of tea tree oil poisoning.

However, the elevated BUN and persistent dehydration suggests that this cat may have had renal damage unrelated to tea tree oil intoxication.” [emphasis added]²⁸

So, all indications point to this being another instance where the issue is overdosing with full-strength product, rather than the oil itself being toxic.

Claim #10 – Camphor

What is Camphor?

Camphor is a white, waxy solid traditionally made from the bark of the camphor tree that has a very strong odor (similar to menthol).

People use it as a medicine, antifungal, and insect repellent.

Dr. Shelton writes: “Listings cautioning against the use of camphor, never qualify if it is the constituent or the essential oil they are referring to.

In high concentrations, it can pose health risks, and is listed as toxic in regards to humans.

Camphor (many species) essential oil is not recommended for use within Veterinary Aromatic Medicine.

Camphor as a chemical constituent [ingredient] can be found in small percentages within many essential oils known to be safe for use with animals, however oils high in camphor content, are often not used (Spike Lavender).”²⁹

Check out Tisserand and Young’s textbook , “Essential Oil Safety“, since it has a lot of data about camphor that’s worth further investigation.

Claim #11 – Methyl Salicylate (Birch, Wintergreen)

What is Methyl Salicylate?

Methyl salicylate is a colorless, thick, sticky liquid produced by many species of plants, mostly wintergreens. You can also get it in synthetic form.

Methyl salicylate has a sweet, fruity odor similar to root beer, and is in fragrances.

It’s also a flavoring agent and is familiar to most people as the minty flavor in mint candies.

Methyl Salicylate is Like Aspirin

young silver tabby cat - methyl salicylate in oil is toxic to cats

Methyl salicylate is similar to aspirin (acetylsalicylic acid).

It has therapeutic value (used a lot in deep heating creams for sore muscles in humans) but has the same toxicity as aspirin.

According to Timothy Miller, N.D., R.A., “Effectively, 1 drop of wintergreen essential oil = ~81 mg of aspirin [a baby aspirin].”³⁰[emphasis added]

In a report by Sharon M. Gwaltney-Brant, DVM, PhD, DABVT, DABT, she makes clear there’s a “narrow margin of safety in these animals” when it comes to methyl salicyclate.

“The reported therapeutic dosage of aspirin in dogs is 10–20 mg/kg bid. Single doses of 25 mg/kg have been shown to initiate gastric bleeding in dogs, suggesting that aspirin has a narrow margin of safety in these animals…

…The therapeutic dosage in cats is 10–20 mg/kg every 48 hours. Cats are deficient in glucuronyl transferase, which prolongs excretion and results in a half-life that is dose dependent.

Although the half-life of doses of 5–12 mg/kg can range from 22–27 hours, a dose of 25 mg/kg has a half-life of 44.6 hours in cats. This compares to a half-life of 8 hours in dogs [emphasis added]. ³¹

Conclusion From This Report

The conclusion of this report is that it takes a lot longer for a cat’s body to process anything with methyl salicylate than other animals.

This makes it dangerous since the margin for error is too risky to use on cats.

The small margin of error in dosages makes oils containing methyl salicylate, like birch and wintergreen, unfit for home use with any animals, especially cats.

Claim #12 – Oils That Nobody Should Use!

Dr. Shelton lists some oils notable for being too dangerous for humans or animals in their pure, highly concentrated forms.

Some are great for people, but not good at all for cats. Garlic, for example, in concentrated oil form can cause blisters on the skin.

Using its bulb and leaves, either raw or cooked, has health benefits for people but cats don’t digest it well.

Russian Blue cat sitting in grass looking up

So, don’t put these on a cat’s fur or skin or give them any to eat.

There are people who claim they use some of these for their cats with no problem, but veterinarians who know these oils do not recommend it.

Don’t Use the Oils on This List!

This list is from Dr. Sheldon’s article, “The Science Behind Cats and Essential Oils”.

These contain substances that make it dangerous for the average person to use.

It’s best to avoid them and use other products that are safer for killing fleas.

Bitter Almond

Boldo

Calamus

Garlic

Horseradish

Mustard

Sassafras

Wormseed (Chemopodium)

Pennyroyal

The Wrong Way to Use Essential Oils

All the evidence I’ve found so far shows that the main problem with essential oils is the people…

using poor quality products

using them in ways other than their intended use

overdosing

sphynx cat; using essential oils on cats

using them directly on a cat’s skin

putting concentrated oils on fur, which the cat licked off and swallowed

using any oils or flea control products on a sick or pregnant cat

using any oils or flea control products on a kitten under six weeks old

A sick or pregnant cat, or kitten under six weeks of age, can’t handle what a healthy adult cat’s body can.

If your cat has an underlying kidney problem, he may not be able to eliminate even a small amount of an oil’s components.

By contrast, a healthy cat can handle the diluted amounts in commercial flea and tick products.

The point here is that you’re responsible for how you use any product on or around your cat, including essential oils.

Treat essential oils the same way you should drugs… carefully and with the guidance of a knowledgeable veterinarian.

Drugs can be very beneficial or very deadly… so can essential oils.

Diffusion vs. Direct Application

Diffusing oils into the air is quite different from applying them directly to your cat’s skin or fur.

When using a diffuser, use common sense and leave a door open so your cat can get out of the room.

If he doesn’t like it, he’ll leave (we felines are pretty smart that way!)

For your own safety, don’t allow the fumes from a diffuser to build up over hours (the same is true for candles).

Limit how long you use it at any one time and make sure you have good air circulation.

Again, if your cat, dog or any other pet has health problems, is pregnant or very young (under 3 months old), don’t expose them to strong oils in any form, including diffusers.

The Trouble with Stories About Essential Oils Being Toxic

The only evidence we currently have of these various oils being dangerous is anecdotal… people telling experiences they’ve had using essential oils on or around their cats.

Unfortunately, we don’t know in these specific cases if there were other underlying problems or influences that affected the reaction of the cat.

This leads to some questions that have no clear answers, like…

silver tabby cat drinking water from a bowl

Were any of the affected cats sickly or did they have compromised immune systems?

Did the person use fresh, good quality oil on their kitty?

How much did they use?

Did they carefully follow the manufacturer’s instructions?

woman holding dropper of CBD oil near cat

Did the cat swallow it? If so, how much?

How did the person apply the oil… on the skin or by mouth?

Did the cat inhale it?

Nobody can draw accurate conclusions about what made these cats sick until there are answers to these and other questions.

In Conclusion

Orange, ginger tabby kitten looking up, backwards

Ultimately, using any product on a cat is something you have to do carefully.

If your cat is healthy and you’re working with a vet who can advise you on proper quality (authentic pure therapeutic grade), dilution (never strong), quantity, and proper application method, most essential oils can be effective and safe for cats.

Discover more about your cat’s health at “Cat Health“.

Sources

Sources used on this website are either primary or secondary.

Primary sources are always preferable and have the most reliable information because they’re original and directly referenced.

Scientific abstracts and data are good examples of primary sources.

Secondary sources are weaker because they usually consist of opinions or articles that give no sources of their own, however, sometimes they refer to primary sources.

When I use secondary sources, most are those with some authority, such as veterinarian or cat behaviorist books and articles.

List of Sources

A-E

“Australian tea tree (Melaleuca alternifolia) oil poisoning in three purebred cats“, by K. Bischoff and Fessesswork Guale, J. Vet. Diagn. Invest. 10:208-210 (1998)

“Can You Use Essential Oils With Cats? The Experts Weight In“, by Amanda Lattin (BA, MAT, DIP. AROMA., MH, RA), ACHS Aromatherapy Program Chair, Catrina Mianecki (BS, MED, MS, CERT. AROMA. L.AC), Marilyn Addison (BA, RA), American College of Healthcare Sciences, 29 March 2018

“Caveat Emptor: Safety Considerations for Natural Products Used in Arthropod Control“, American Entomologist, Vol. 48, No. 1, Spring 2002, pp. 9-10

“Controlling Ticks and Fleas with Linalool“, 2013

“EPA Reregistration Eligibility Decision-Limonene“, 2001, pp. 10-11, 196-200

“Essential Oil“, Merriam-Webster Dictionary

“Essential Oil Safety Pages“, The Tisserand Institute

“Eucalyptol“, Wikipedia

F-Z

“Idiosyncracies of Drug Metabolism in Cats: Effects on Pharmacotherapeutics in Feline Practice”, by Jeff R. Wilcke, DVM, MS, Veterinary Clinics of North America: Small Animal Practice-Nov. 1984, Vol. 14, No. 6, Science Direct

“Melaleuca alternifolia (Tea Tree) Oil: a Review of Antimicrobial and Other Medicinal Properties“ by C.F. Carson, K.A. Hammer, and T.V. Riley, Jan. 2006

“Phenol“, Wikipedia

“Salicylate Toxicosis in Dogs and Cats”, Standards of Care Emergency and Critical Care Medicine, by Sharon M. Gwaltney-Brant, DVM, Vol. 4.7, August 2002, VetNetInfo.com

“The Science Behind Cats and Essential Oils”, by Melissa Shelton DVM, Veterinarians Westminster, Maryland, Carroll County Veterinary Clinic (carrollcovet.com), posted January 31, 2018

“Tea Tree Oil“, Drugs.com, 17 June 2019

“Wintergreen the Good the Bad the Ugly”, by Timothy Miller, N.D., R.A., Naturopathic Doctor News & Review, 30 June 2015

Updated November 15, 2023

Who Is Skye Blake?