What You Don’t Know About Essential Oils Can Burn You. Literally.

If you’ve been reading my blog articles for any length of time, by now you know where I stand on essential oils. I think they are incredible extracts of nature, but at the same time need to be treated with respect. In this article you’ll read about how using essential oils irresponsibly can burn you.

Some Constituents in Essential Oils Can Cause Chemical Burns

For all of their wonderful characteristics and abilities, the bottom line is essential oils are derived from plant matter and can be toxic in certain situations. Treat them with respect and observe precautions, and you will be fine.


A very popular essential oil is cinnamon, three varieties of which exist: cinnamon bark and cinnamon leaf (Cinnamomum zeylanicum or verum), and cinnamon cassia (Cinnamomum cassia). In fact, most of the ground cinnamon herb and cinnamon sticks sold in grocery stores is actually cassia, not the zeylanicum or verum species. (1)

Cinnamon leaf and bark essential oils are known for their pleasant aroma as well as warming, stimulating and energizing qualities. Really, this spice needs little introduction. Cinnamon essential oil is also a very powerful antibacterial, antifungal, antimicrobial, antiviral, and antiseptic agent. In fact, cinnamon is an ingredient in the Young Living Thieves® oil blend.

Kyriel Rook recalls an incident in the past where she received second-degree chemical burns from concentrated cinnamon essential oil, most likely cinnamon bark. She had accidentally spilled a few drops on her hand, then wiped that hand across her face. Within the next few seconds, the redness spread upward from the point of contact until it almost reached her eyes. (2)  In this blog, we’ll learn what chemical constituents were responsible for her burns.

There are important precautions you need to observe when working with the cinnamon types of oils. As you know, I am pretty adamant about diluting any essential oil prior to applying it to the skin. Any ethical aromatherapist would give you the same advice. The thing is, each essential oil has a unique combination of chemical constituents, which give the oil its character. The dilution guidelines are just that – guidelines. There are sometimes exceptions to the rules.

Generally speaking, two percent dilution is typically considered safe for adult aromatherapy for a wide variety of essential oils. For children and the elderly, one percent dilution is more appropriate. Going above two percent dilution is appropriate for local applications and treating acute conditions for a brief period of time.


Cinnamon Leaves – Source: Wikimedia Commons

When applying cinnamon leaf essential oil to the skin, Robert Tisserand and Rodney Young recommend a dermal maximum of 0.6%. (3)

If six drops of essential oil per ounce (30 ml) of carrier oil is one percent dilution, then 0.6 percent works out to 3.6 drops per ounce (6 x 0.6), which works out to two drops per half-ounce (15 ml) of carrier oil, or two drops per tablespoon.

For cinnamon bark, however, Tisserand and Young recommend a dermal maximum of a scant 0.07%. (4)

This equates to 0.42 drops per ounce of carrier oil (6 x 0.07 = 0.42). Therefore, two drops of cinnamon bark per five ounces of carrier oil is approximately equal to 0.07% dilution. For reference, a cup is eight ounces. Four drops of essential oil in slightly more than a cup of carrier oil is an extremely low percentage. Going back to the story above, let’s say that Kyriel spilled five drops of cinnamon bark oil on her hand. In order to dilute that particular essential oil to a safe 0.07 percent concentration, she would have had to use around 12 ounces of carrier oil, a whole 1.5 cups. That’s a lot of vegetable oil.

Here is a link to an essential oil dilution calculator. It’s convenient and easy-to-use.


Cinnamon Bark – Source: Wikimedia Commons

Let’s talk about why cinnamon essential oil needs to be diluted so much. The two most prominent chemical compounds in cinnamon bark oil are: Cinnamic aldehyde (cinnamaldehyde), which is a phenylpropanoid aldehyde, and Eugenol, which is a phenylpropanoid phenolic ether. (5)(6)(7)

Cinnamon bark essential oil is about 90% cinnamaldehyde. Concentrated cinnamaldehyde is a dermal (skin) irritant, and the chemical is toxic in large doses. (8)

Cinnamon leaf oil’s two main constituents are Eugenol and Eugenyl acetate. (9)  These two are less irritating than cinnamaldehyde. Cinnamon bark oil has a greater concentration of cinnamaldehyde than eugenol.

Cinnamon bark oil is considered to be the greater skin irritant as its chemical components make it a dermal toxin; cinnamon leaf oil, although relatively non-toxic, could produce a reaction due to some presence of the cinnamaldehyde in the oil. (10)

Eugenol and eugenyl acetate are considered mildly irritating and sensitizing to the skin (dermis) and mucous membranes. Interestingly, the presence of eugenol has been found to mitigate sensitization to cinnamaldehyde. (11) This is possibly one of the reasons why cinnamon leaf oil is less irritating in general compared to cinnamon bark. Cinnamon leaf contains approximately 0.6 to 1.1 percent cinnamaldehyde and 69 to 87 percent eugenol, whereas cinnamon bark, cassia bark, and cassia leaf contain anywhere from 63 to as much as 90 percent cinnamaldehyde. (12)


Cinnamon Bark Essential Oil – Source: Wikimedia Commons

You probably remember the “cinnamon challenge” from a few years ago. Teenagers were snorting cinnamon powder and video recording their antics with the spice. The physical reactions to inhaling the cinnamon were not exactly pleasant. It’s quite possible that the mucous membranes of the nasal cavity and throat of these young people were being irritated by the presence of cinnamaldehyde.

Clove Bud

Another “hot” essential oil is Clove Bud (Eugenia caryophyllata). It’s not quite as irritating as cinnamon bark or cassia, but precautions need to be taken still. The chief chemical components in clove bud oil are Eugenol, B-Caryophyllene, a-Caryophyllene and Eugenyl acetate. Tisserand and Young recommend a dermal maximum dilution of 0.5 percent. (13)

Alpha and Beta-Caryophyllene belong to a class of chemicals called sesquiterpenoid alkenes. B-Caryophyllene is somewhat sensitizing to the skin, potentially causing dermal irritation or contact dermatitis. Eugenol is the main constituent, present between 73 and 97 percent of the oil, with B-Caryophyllene being the second most prominent constituent between 0.6 and 12.4 percent. (14)  For this reason, the presence of eugenol is of greater concern.

Tisserand and Young indicate that when using clove bud essential oil, there is a moderate risk for mucous membrane irritation, inhibition of blood clotting and potential drug interaction hazards. They also do not recommend the use of clove bud in children under two. (15)

The woman I mentioned in a previous paragraph, Kyriel Rook, says, “Please don’t spill clove oil on your skin. Your whole forearm will go numb. I dilute one drop in a cup of water to dull the pain of a toothache.” (16)  Why exactly does this happen? The aromatic clove contains eugenol, which is often used as an analgesic and antiseptic in a variety of dental health applications. (17)


Dried clove buds – source: Flickr


Oregano essential oil, Oreganum vulgare, is a particularly strong and pungent oil. We’ve all at some point put the oregano herb on pasta or pizza. As a dried herb, this is fine. The essential oil contains Carvacrol, p-Cymene, Gamma-Terpinene, and Thymol. (18)  Carvacrol is the most prominent constituent, present at a concentration from 61 to 83 percent of the oil. The remaining components are present at concentrations below 10 percent. Carvacrol is a substituted phenol, like eugenol, so it is potentially corrosive to tissue. Oregano essential oil can be irritating to individuals who have dermatitis or who are allergic to carvacrol and/or thymol. (19)

Tisserand and Young warn that Oregano essential oil is contraindicated during pregnancy and breastfeeding. There is a moderate risk for mucous membrane irritation. Oregano may inhibit blood clotting and pose a drug interaction hazard. There is a moderate risk of skin sensitization, and Tisserand and Young recommend a dermal maximum dilution of 1.1%. They advise not to use topically on children age two or younger or for those with damaged or sensitive skin. (20)


Oregano – source: Wikimedia Commons

I want to make an important distinction: people seem to think oil of oregano and oregano essential oil are interchangeable. The two are not the same thing. Oil of oregano is basically olive oil (or another oil) infused with oregano herb. In other words, herbal cooking oil. It’s fine to ingest and use in cooking. On the other hand, oregano essential oil is made from the steam distilled oregano herb, and as such, is highly concentrated. If you put oregano essential oil in whatever it is you happen to be cooking, my concern is that the heat would destroy the essential oil molecules and render the oil ineffective. But then again, I assume folks are only doing this to add flavor to the food, and aren’t concerned with aromatherapeutic properties. I still think using an herbal-infused vegetable oil is the way to go.

In 2014, Dr. Oz featured an episode on his show where he talked about “oregano oil” being “nature’s powerful antibiotic.” Dr. Oz was talking about oregano essential oil, but he mistakenly referred to it as oil of oregano. In his video, he says you can make oregano hand sanitizer by “combining 10 drops of oregano oil with two tablespoons of coconut oil.” (21)  Since Tisserand and Young recommend a dermal maximum of 1.1 percent dilution, 10 drops per two tablespoons is approximately equal to 1.67 percent, which is well over the recommended limit. To dilute the oregano essential oil at or below 1.1 percent would amount to using no more than 6 drops of the essential oil in an ounce (two tablespoons) of carrier oil.

Another piece of advice from Dr. Oz is to “Try adding a drop or two of oil of oregano on your toothbrush with or without toothpaste.” Again, assuming he was referring to oregano essential oil, this is not a good idea. The gums and lining of the mouth are mucous membranes and are susceptible to irritation. Oregano essential oil may smell good, but the stuff is gnarly, in my opinion. I’ll take a pass.

I’ll add that oregano is a very effective antiseptic, but in my opinion, not very skin-friendly. I would recommend tea tree essential oil over oregano as it is less irritating, yet still a potent antibiotic.


Next is Lemongrass essential oil (Cymbopogon citratus / Cymbopogon flexuosus). This particular essential oil smells similar to lemon but is not a member of the citrus family.

The major constituents of lemongrass essential oil are Geranial, Neral, Geranyl acetate and Geraniol. Geranial and Neral are aldehydes, Geraniol is an alcohol, and Geranyl acetate is an ester. Tisserand and Young recommend a dermal maximum dilution of 0.7 percent for lemongrass in order to avoid skin sensitization. This oil is not recommended for children under the age of two, or for individuals with sensitive or damaged skin. (22) (23)

Lemongrass is recommended for acne, athlete’s foot, excessive perspiration, flatulence, insect repellent, muscle aches, oily skin, etc. As long as the oil is diluted at or below 0.7 percent (4 drops per ounce of carrier), this is fine.

In a previous blog article, I talk about a reaction I had to lemongrass. It’s strong stuff. You don’t want to get any of it on your skin undiluted. If you do, you’ll want to remove the essential oil with a carrier oil, preferably. Water will not help because essential oils are hydrophobic; they do not dissolve in water. If you have no carrier oils in your immediate possession, you could use liquid soap or another fatty substance such as milk or coffee creamer to remove the essential oil.


Lemongrass – source: Wikimedia Commons

Photosensitivity – Another Type of Burn

Many people who use essential oils topically are unaware of a different type of burn – photosensitivity, also known as phototoxicity. A number of citrus and other oils can cause photosensitivity, that is, increased susceptibility to sunburn, for as long as 24 hours after application. Below is a list of photosensitizing essential oils:

  • Angelica & Angelica Root (Angelica archangelica)
  • Bergamot (Citrus bergamia, Citrus aurantium, Citrus aurantium var. bergamia)
  • Grapefruit (Citrus x paradisi)
  • Lemon (cold-pressed) (Citrus x limon, Citrus limonum)
  • Lime (cold-pressed) (Citrus x aurantifolia, Citrus x latifolia, Citrus medica)
  • Orange (cold-pressed) (Citrus sinensis)
  • Wild (Bitter) Orange (Citrus x aurantium, Citrus aurantium var. amara)
  • Mandarin Leaf (Citrus reticulata, Citrus nobilis)

These oils are photosensitizers due to the presence of a class of chemicals known as Furanocoumarins. Bergamot contains the furanocoumarin bergapten, a dominant photosensitizer, that can cause severe reactions. Whenever possible, buy Bergamot that is Bergaptene-free, or FCF (furanocoumarin-free). (24) (25) (26)

Citrus oils that are steam distilled instead of cold pressed, are non-phototoxic. This is because the furanocoumarins are substantially reduced by the fractional distillation process, due to their low volatility. In other words, steam distillation does not carry the furanocoumarins out of the raw plant material, unlike cold pressing. Bergaptene-free or FCF Bergamot is a prime example. (27)



Essential oils, when treated with respect and guidelines are observed, are a great compliment to existing health practices. The information and anecdotes above are not intended as scare tactics, but rather to educate and inform essential oil consumers of potential risks.

For more safety information, aromatherapist Emily Carpenter has a webpage of answers to common essential oil safety questions. Check it out here. She also hosts a page that describes various essential oil injuries. Definitely worth a look.

Do you have any questions or concerns about the information I’ve presented here? See something you feel might be inaccurate? Want to share stories about adverse reactions you may have had in the past? I welcome your comments in the form below.

And to get your virtual hands on a copy of my FREE ebook “Essential Oils Made Easy,” head over to and subscribe.

Thank you for your time,

First name (white ink)

Photo credits/attribution

Cinnamon Leaves: By L. Shyamal (Own work) [CC BY-SA 3.0 (, via Wikimedia Commons

Cinnamon Bark: By Miansari66 (Own work) [Public domain], via Wikimedia Commons

Cinnamon Bark Essential Oil: By Itineranttrader (Own work) [Public domain], via Wikimedia Commons

Clove Buds:

Oregano: By Garitzko (Own work) [Public domain], via Wikimedia Commons

Lemongrass: By Vaikoovery (Own work) [GFDL ( or CC BY 3.0 (, via Wikimedia Commons


(1), (3), (4), (6), (9) Cinnamon Essential Oil

(2), (16) The Dangers of Essential Oils And How to Cope With Them

(5) Aromatherapy for Bodyworkers. Jade Shutes, Christina Weaver. 2008. p. 336.

(7), (11), (12) Essential Oil Safety, Second Edition. Robert Tisserand, Rodney Young. 2014. pp. 248-250, 527-531, 556-561.

(8) Cinnamaldehyde

(10) Cinnamon Essential Oil Profile

(13), (15) Clove Bud Essential Oil Profile

(14) Robert Tisserand and Rodney Young. pp. 254-256, 520-521, 556-558.

(17) 12 Clove Oil Benefits & Health Uses You Didn’t Know About

(18), (20) Oregano Essential Oil Profile

(19) Tisserand and Young. pp. 375-376, 517-518.

(21) Oil of Oregano Guide

(22) Lemongrass Essential Oil Profile

(23) Tisserand and Young. pp. 334-335, 564-568.

(24) Do Essential Oils Really Cause Sunburn? The Truth Behind Photosensitivity

(25) Phototoxic Essential Oils – which ones to avoid when out in the sun

(26) List of Phototoxic Essential Oils

(27) Tisserand and Young. pp. 84-85.

Categories: Essential Oil Safety, Essential Oils and BlendsTags: , , , , , , , , , , , , ,


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