Book review: The Chemistry of Essential Oils Made Simple

At almost 850 pages, there’s plenty of reading here. Unfortunately, this book is replete with errors. There are innumerable mis-spellings of the names of chemicals. Terpinen-4-ol is an alcohol, not a phenol, and bergamotene is a terpene, not a furanocoumarin. On page 374 we read that “Coumarins are thought to be antispasmodic, as are many other esters.” Coumarin is not an ester. Stewart mentions that myrrh oil is rich in ‘furanoid compounds’ – well yes, it is indeed rich in FURANS, and he goes on to say that “furanoid compounds can amplify ultraviolet light and can make an oil phototoxic.” (p23/24). Well, I don’t know why he wants myrrh oil to be phototoxic, but it isn’t, because it contains no FURANOCOUMARINS. Using the term ‘furanoid compounds’ fails to make a vital distinction – between (phototoxic) furanocoumarins, and (non-phototoxic) furans.

In some cases Stewart seems to have copied mistakes from other sources, without realizing they were mistakes. l-Limonene is quite often given instead of d-limonene, and methyleugenol has curiously disappeared as an essential oil constituent altogether – Stewart does not list it a constituent of any of the oils it is actually found in! Furanocoumarins are frequently cited that may indeed be present in the plant but are not found in the essential oil.

He has made a valiant effort to list the components of 113 essential oils, but the method he used – combining data from various books – is risky. The end result is said to represent a ‘typical’ essential oil, but is rather hit-and-miss, and in many cases does not represent any existing essential oil at all. Some of the total percentages add up to more than 100%. Reporting constituent chemistry from different sources is a challenge I am often confronted with myself, but there are more elegant solutions.

Stewart is highly critical of what he calls the ‘British School’ of aromatherapy, because it espouses the idea that some essential oils can be dangerous, and because, according to Stewart, it “relies on scientific research on animals”. However, he does take on board the idea that some furanocoumarins are phototoxic. Stewart perhaps does not realize that phototoxicity in essential oils is almost entirely based on RIFM research using pigs, and much of the ‘French’ information about essential oil constituents that Stewart cites is based on animal research. If the book was properly referenced, this would be obvious. He also criticizes the British for “usually applying only certain compounds isolated from essential oils rather than the whole oil.” (p4) It is difficult to fathom from where he plucked this outrageous notion!

There is a massive amount of information here, but there is not a single scientific reference to back up any of it. The result is an uncomfortable mix of fact and fiction. The book perpetuates the myth that any dangers of essential oils (apart from phototoxicity) only apply to what he calls ‘perfume grade’ oils, which, according to Stewart, British aromatherapists like to use! I’m not sure then, who buys all the independently certified organic essential oils sold in Britain. There is no ‘perfume grade’ of essential oil (on either side of the Atlantic), nor is there a ‘therapeutic grade‘.

[The grades that do exist are various organic certifications, ISO standards, BP (British Pharmacopeia) standards, and FCC (Food Chemicals Codex) standards.]

Stewart does humanity and science a disservice by alleging that it is impossible for an essential oil to cause an allergic reaction: “Occasionally, a person receiving essential oils claims to have had allergic reaction to them….such a reaction is never allergenic…they are usually therapeutic and indicate the initiation of a cleansing, healing process.” (p451) Stewart goes on to explain his hypothesis that essential oil constituents cannot be allergenic, because they are not composed of amino acids. No, they are not composed of amino acids, but yes, they can in fact cause allergic reactions, because an essential oil constituent such as cinnamaldehyde (known as a ‘hapten‘) can combine with proteins in the skin and can then be recognized by the immune system as an allergen. This is not new science, and Stewart’s bending of the facts to suit his world view is shameful and potentially dangerous.

There is a lot of information in this book and it is by no means all wrong, but the fact-to-error ratio is too rich for me, and the way he plays with words to make ‘his truth’ look like fact is disturbing. On page 462 he states: “There has never been a documented instance of antigen-antibody response (i.e. sensitization) to an essential oil. Essential oil antibodies have never been found or detected in anyone. Never.” The last part is true, but only because (a) you can’t have an antibody to an essential oil, only an essential oil constituent (is this genuine ignorance of basic biology, or just more fact-bending?), and (b) no scientist has ever found antibodies to essential oil constituents, because no scientist has ever looked for them. Perhaps the clinical reality of an allergic reaction needs no proof. Here are two documented cases of allergic reaction to cinnamon bark oil:

Ackermann L, Aalto-Korte K, Jolanki R et al 2009 Occupational allergic contact dermatitis from cinnamon including one case from airborne exposure. Contact Dermatitis 60:96-99

Sánchez-Pérez J, García-Díez A 1999 Occupational allergic contact dermatitis from eugenol, oil of cinnamon and oil of cloves in a physiotherapist. Contact Dermatitis 41:346-347

The IFRA safety standards require that cinnamon bark oil should not be used on the skin at more than 0.6%, to avoid allergic reactions.
Essential Oil Safety – a rebuttal
Stewart is critical of my book, Essential Oil Safety. Here are some of his comments:
 Much of the research cited is on the toxic effects of single components of an oil, which is an invalid application of science. This is an incredible statement, considering that most of Stewart’s book is devoted to explaining essential oil chemistry, and the relationships between constituents and therapeutic properties. On page 468, for instance, Stewart says: “essential oils rich in phenols should be used with caution when applying to the skin.” If extrapolating single component data to whole essential oils is not OK when I do it, why is it OK when Stewart does it?

Furthermore, as the authors point out, in all of the studies they cite, the data are for animals (not people) and/or the tests were not for the whole oil but for isolated compounds of an oil. These types of studies are not valid indicators of the behavior of oils in actual practice. (p21/22) This is simply not true, and is not stated anywhere in the Essential Oil Safety text. There are many studies cited in Essential Oil Safety where whole essential oils were patch-tested on individuals (such as the two reports for cinnamon above), and there are many cited cases of poisoning from whole essential oils. And, see my previous comment.

There are two places where I have been mis-quoted:

1) In the preface the authors state “this text was largely an extrapolation of toxicological reports from the Research Institute for Fragrance Materials (RIFM).” In other words, this book is based on data that apply only to perfume grade oils which are customarily refined, denatured, and laced with synthetics. (p787)

This is what the preface actually says:
“This book [i.e. Essential Oil Safety] replaces The Essential Oil Safety Data Manual by Robert Tisserand, first published in 1985. This text was largely an extrapolation of toxicological reports from the Research Institute for Fragrance Materials (RIFM).” So , I was not referring to Essential Oil Safety at all, I was referring to a previous, and very much smaller book.

2) These authors state on p ix, “the majority of essential oils we recommend should not be available to the general public”. In their opinion, the majority of essential oils should be restricted only to what they would regard as “qualified aromatherapists.” (p788)

This is what is actually said:
“In the UK and USA at least, it is currently possible to purchase, by mail order, the majority of the essential oils which we recommend should not be available to the general public.” Stewart is trying to make it sound as if I don’t believe essential oils should be available to the general public. Of the 450 odd essential oils produced today, I do believe that a dozen or so should not be publicly sold, because they are so toxic. To suggest that I am not in favor of ordinary people having access to essential oils is just incredible. David Stewart, what do you think I have been doing for the past 40 years? Why is there a brand of essential oils called Tisserand Aromatherapy? Why are these essential oils available to anyone? Why did I write The Art of Aromatherapy in 1977? And what was I thinking when I wrote a book called Aromatherapy for Everyone in 1988?

In both cases, by omitting the first part of the sentence, the meaning has been completely changed. And in the second quote, two words were omitted to further change the meaning. It’s sad that someone should invest so much energy in writing a comprehensive text, and then sabotage it by trying to bend the truth to suit a commercial agenda. (And if there is no commercial agenda, why are Young Living products mentioned throughout the book?)

By |2018-04-24T20:26:01+00:00August 24th, 2012|Book reviews|31 Comments

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  1. Lora August 24, 2012 at 4:31 pm

    WOW!!! Just WOW!!

  2. Marge Clark August 24, 2012 at 8:35 pm

    Thank you, Robert!!!!!!!!!!!!!!!

  3. Darlene August 24, 2012 at 11:35 pm

    THANKS sooooo much for your dedication to the truth! You are GREATLY Appreciated!

  4. Joanne Lang August 25, 2012 at 12:22 am

    Thank you for this great article, chemistry is often the least favourite aspect of aromatherapy training for students , so it is imperative that the information they receive is clear and accurate. Thank goodness for you and Joy Bowles books to offer to my students. Very much looking forward to the new edition of essential oil safety any news on when this will be available?.

  5. robert August 25, 2012 at 12:41 am

    Thank you all for your support. The new Essential Oil Safety manuscript will be in the hands of the publisher (Elsevier) by the end of September, and they reckon a project takes 12 months to publish, so it’s looking like September 2013. I am now looking out for conferences to speak at and other speaking engagements for late 2013 and early 2014.

  6. Stephanie August 25, 2012 at 5:34 am

    Robert, thank you so much for your dedication to the wonderful world of chemistry pertaining to Essential Oils. I love that you have quoted particular parts from stewarts book,it will help me clearly point out the inadequate information to others as well. Thank you again for sharing and for your HONESTY 🙂

  7. The Nova Studio August 27, 2012 at 2:24 pm

    Yikes, these are some serious mistakes. Looking forward to hearing more about your new book edition!

  8. Eliane September 4, 2012 at 10:57 am

    while reading your text i thought: sounds like somebody from a certain essential oil company wrote this book. and at the end you mention this company which offers “therapeutic grade” essential oils, if possible applied neat on everybody’s skin, in most of the “diseases” and conditions preferably thyme ct thymol, savory and wintergreen – as seen in their aromatherapy massage training dvd. all in all i counted at least 6 ml of PURE of those and the like essential oils on one single massage session shown on the dvd. wow!

  9. Ericka September 9, 2012 at 10:58 pm

    Hi Robert,
    thankyou for this honest dirrect informative account of the correct information regarding toxicity
    and essential oils. A valuable resource and knowledge base for begginer students like me looking to clear up the murky waters and conflicting information given in so much material.

  10. joy musacchio October 9, 2012 at 6:13 pm

    Fantastic review Robert. Thank you so much. Looking very forward to your book.

  11. Katharine Koeppen October 18, 2012 at 4:26 pm

    Go, Robert!

  12. Ann Wooledge October 18, 2012 at 6:48 pm

    Oh my goodness! I am amazed and impressed that you were able to keep such a “cool head” while you wrote this review. I would have been jumping up and down on any table I could find. Before I read your review, I took a close look at the cover of the book – usually a good indication of what will be inside. I was immediately taken back by the obvious marketing ploys that looked like something from an MLM and admit I was somewhat surprised because the author’s name is not unknown in the aromatherapy industry – not as well known or as respected as yours – but known nonetheless. This looks to me like a strong effort by one MLM company who is struggling, but I’m still surprised a professional aromatherapy “authority” would sabotage their reputation as well as further muddy up the truth of our industry solely for profit. Thanks once again Robert for bringing clarity to an already suffering reality in our industry that will fall to the wayside if books such as this and MLM companies such as that continue to spread their misinformation.

  13. Mary Humphrey October 19, 2012 at 5:27 am

    Thank you, Robert! Wow!

    I am looking forward to your new book!

  14. Amy December 27, 2012 at 11:34 am

    Thank You! I have resisted purchasing this book because I felt the author was trying to be an expert and didn’t like the YL connection. Thank You!!!!

  15. Patty Nickolaus January 23, 2013 at 4:14 pm

    Mr. Tisserand, Thank you for your expertise and effort to bring clarity to those of us who would use this book as reference to guide our use of and share information concerning essential oils. This is the first book I ever really “devoured” in my search for information to assist me in learning to use essential oils. I do not/never have/never intend to use EO’s marketed by an MLM company but this book seemed to make the information interesting and easy to understand for a lay person as myself. I appreciate the corrections you have made available.

  16. Cynthia Hillson February 9, 2013 at 6:20 am

    THANK YOU for your blog and all the credible work you do for the essential oil industry. Personally I have lots of issues with the mlm companies, perhaps more so than others since my books, teachings and products are based on Bible stories in which I pair essential oils to get a fuller experience of them. Not to go into detail but I had e-mail conversations with Stewart on errors in his healing oil book. I’ve felt I should write a blog on the errors but I’m not wasting my time. The people who are part of the essential oil mlm’s are dedicated to their companies, although they all seem to be brainwashed, sorry my opinion. Hmmm, perhaps I should write that blog.

    I’m looking forward to your new book.

  17. Kelly February 15, 2013 at 8:39 am

    Thanks so much Robert, appreciate your time and energy, and your wisdom! The author certifies people in RDT Therapy, so not much to be expected by way of a book filled with errors etc. Amazing!

  18. Susan Stype February 15, 2013 at 11:42 am

    Yes, Robert thanks for your continued education and use and safety of essential oils and aromatherapy.

  19. Lisa Browder February 15, 2013 at 7:37 pm

    Great review. Very thoughtful and, as usual, totally credible – unlike the other. Thank you, Robert.

  20. CC March 25, 2013 at 9:50 am

    Dear Robert,
    I don’t know where you get your info. Just because you appear to have the knowledge, it does not mean you do. Just because you post a rebuttal, it does not mean that you are accurate. FDA approves medicine every year, and the following year is recalling it, just because they were harmful, so someone was wrong to it’s accuracy and chemical reaction. I am not a scientist, I don’t know what each oil contains, so I can’t prove you right or wrong.

    All I know is that I got myself out of many health issues by using Young Living Essential Oils such as depression, panic attacks, paralysis, kidneys problems, multiple cysts, candida, menopause, … and many more. No one was coaching me, I simply got a book Reference Guide for Essential Oils, tested myself with ZYTO regularly and used exactly what ZYTO was reporting. I found that I would have “allergic reaction” with any other brand of essential oils, but Young Living, although at first I would have a reaction and skin irritated. However, the longer I used the oils, the less reactions I experienced, until they were all gone, just as Dr. Stewart writes in his book, which I got AFTER I already got rid of all the symptoms.

    From my personal experience it makes sense what Dr. Stewart states that a person will experience allergic reaction if an oil is adultered, as many brands are. Or that there will be a reaction during the detoxing process. It took me about a year to get myself out of all medicine. Now I am vibrant, full of energy, happy, I look 10 years younger, all the lines around my eyes disappeared, and I use exclusively Young Living products, as they are the best, and they are therapeutic to me. Thieves products are absolutely amazing, so are the personal care, all containing essential oils, all healing to the body, mind and spirit.

    I think you are the one who is doing a big disservice to the public. If I listened to you I still would be taking meds by a dozen. Instead, as a side effect I even got rid of my cellulite by using cinnamon bark, lemongrass, citrus fresh, helichrysum and grapefruit, all Young Living oils.

  21. robert March 25, 2013 at 11:37 am

    Dear CC,

    Where do I get my information? From reading research papers about essential oils, which I have been doing for more than 40 years. And yes, just because I posted a rebuttal doesn’t mean I’m right, though I’m not sure what the FDA has to do with it. Did I say somewhere that people should use conventional medicines in preference to essential oils?

    You seem to have interpreted my post as an attack on Young Living, which it is not, it is a book review that describes inaccuracies in the book. However, I am by no means claiming that everything in Dr. Stewart’s book is wrong or misleading.

    If you found a book that helped you in addressing some health issues, then I’m genuinely delighted to hear that! I have met thousands of people who found my book The Art of Aromatherapy inspirational, life-changing (and often career-changing) so I know how much influence a book can have.

    If you feel that there is something unique about Young Living oils, then we can simply agree to disagree on that point. Since YL buys most (not all, but most) of its essential oils from the same international sources as most other aromatherapy and perfumery businesses, the idea that they are in a league of their own has never made sense to me.

  22. CC March 28, 2013 at 3:34 pm

    Thank you for this explanation and the reply Robert. Because of the health changes and healing, I changed my career. I enrolled in a doctorate degree program in naturapathy a year ago. I read some other articles you posted, and you stated that there is no evidence of essential oils repairing eyes or vision. Well, by using Helichrysum, Lavender and Boswelia Carteri around my eyes daily, I completely got rid of my glasses that I used to wear since 1st grade. That’s evidence to me! Perhaps there is something that science cannot explain? I don’t know. All I know is how Young Living oils helped me and my family. I do believe there is something special about Young Living EO, because I used other brands with little or no effect.

    I don’t know if YL buys their oils from the same source, I know they don’t dilute the oils or change its integrity, I watched it being distilled and tested, and bottled. Although you claim there is no classes or grades of oils, Gary Young claims there are. They claim there is an A class, and Young Living actually buys 100% of that class, so there is no more left to buy.

    At any rate, I don’t doubt you are an expert in the field of essential oils, but perhaps you don’t have proper data, therefore forming false opinions? I don’t say that to get you upset, just an observation. The field of essential oils is not regulated by the FDA, and recently they asked Gary Young to set the standards for essential oils for the FDA. Perhaps he is considered the expert in this field.

  23. robert March 28, 2013 at 10:02 pm

    I wish you luck in your degree program. Your use of essential oils around your eyes is indeed evidence to you, but it’s only hearsay to anyone else. You can read my blog post about essential oils and eye safety here:

    Essential oils are not regulated separately by the FDA, they either come under FDA cosmetic legislation, or FDA drug legislation: Standards already exist for essential oils, and these are set by the International Organization for Standardization: Therefore, there is no conceivable reason why the FDA would ask Gary Young, or any other individual, to “set standards” for them. Gary Young has been the subject of an FDA warning letter:, and there is a proliferation of negative internet posts about him ( Some of this may not be true, but when there’s this much smoke you have to suspect there’s a fire burning!

  24. robert March 28, 2013 at 10:05 pm

    I wish you luck in your degree program. Your use of essential oils around your eyes is indeed evidence to you, but it’s only hearsay to anyone else. You can read my blog post about essential oils and eye safety here:

    Essential oils are not regulated separately by the FDA, they either come under FDA cosmetic legislation, or FDA drug legislation: Standards already exist for essential oils, and these are set by the International Organization for Standardization: Therefore, there is no conceivable reason why the FDA would ask Gary Young, or any other individual, to “set standards” for them. Gary Young has been the subject of an FDA warning letter:, and there is a proliferation of negative internet posts about him ( Some of this may not be true, but when there’s this much smoke you have to suspect there’s a fire burning!

  25. jeffrey July 28, 2013 at 7:30 pm

    Hi Robert! I believe when it comes to health and healing, there should be no sacred cows. From that point of view it is good that any information put out on essential oils be looked at with a critical eye, as you did with Mr. Stewart’s book. Having said that, I have read his book. I actually bought it by mistake, originally intending to order a book of almost the same name by David G. Williams. After receiving it where I live overseas I decided to read it, as return shipping would have cost more than the book. I know as one of the recognized authorities on essential oils, your eyes may have gone immediately to what appeared to be some rather glaring errors. I personally was not endeared to the parts of the book that had an underlying tone of promotion for a particular “school” of essential oil use that is quite controversial to begin with. I have no way to judge if neat application of certain essential oils along the spine can have a therapeutic effect. However, as a student of essential oils, I have to go with what is considered “best practice” in the topical application of essential oil, and the Hippocratic concept of “above all, do no harm,” and stick mostly with accepted levels of dilution. Having said that, I did find Mr. Stewart’s book to be interesting and informative when he wasn’t pushing a particular type of aromatherapy. Since your review I have looked at it with a much more critical eye, but do credit him when not erroneous in his information, for both trying to make the chemistry of essential oils easy to understand, and imparting a sense of the sacredness of working with essential oils, a gift from God and nature.

  26. Stacy September 30, 2013 at 9:46 am

    There is a lot of misinformation here. For instance, you said, “Since YL buys most (not all, but most) of its essential oils from the same international sources as most other aromatherapy and perfumery businesses, the idea that they are in a league of their own has never made sense to me.”

    This is absolutely false.

    That being said, I am interested in your new book. I would like more information on essential oil/drug interaction. And I’m sure we can all glean from one another. It’s just too bad you found it necessary to put someone else down to build yourself up.

  27. robert October 3, 2013 at 10:51 am

    Thank you for your comment, Stacy. I’m interested in facts, not in putting people down. Perhaps we are not understanding each other in regard to Young Living. I am saying that, if a company buys from the same sources that many others buy from, there’s no reason to think that their oils are unique. Let’s take the first 10 essential oils listed alphabetically by YL: Angelica, Balsam fir, Basil, Bergamot, Black pepper, Blue cypress, Blue tansy, Cardamon, Carrot seed, Cedarwood.

    Apart from balsam fir, how many of these are from plants grown on a YL farm?

  28. Marian Del Vecchio October 21, 2013 at 8:54 pm

    And we are looking for a book about chemistry “made silmple”.
    Thank you for the post.

  29. Kathleen February 25, 2014 at 12:30 pm

    I’m so glad I finally stumbled upon someone who actually knows his stuff. Knowledge is everything! Of course in finding you who has expertise and truth, I had to go through the cast of characters who just want to buy from them. Stumbling upon websites who through their essential oil recipes get you to purchase from Spark Naturals. Then in finding resources of information you realize they are promoting some great marketing jargon. Then I knew something was amiss. Lo and behold, I found you through other informative sites. I’m so relieved I can finally be able to actually learn about essential oils and the safest way to use them. Safest being of the upmost operative word here. I really don’t care what other people have to say about you in “condemning” another company. They need to get with the knowledge and put their emotions aside. But, to each his own. I prefer to apply oils safely for myself and whomever I want to help. Thank you again. I look forward to purchasing your book.

  30. Elizabeth Giuliacci March 7, 2014 at 7:23 pm

    I am trying to find answers about whether or not it is possible to be allergic to EO’s. I find your information to be most instructive. You said in this post that, “an essential oil constituent such as cinnamaldehyde (known as a ‘hapten’) can combine with proteins in the skin and can then be recognized by the immune system as an allergen”. So cinnamaldehyde is found in cinnamon. Ok, so we stay away from cinnamon oil with people with sensitivities. Are there other constituents that can combine with proteins in the skin? How long is that list?

  31. robert March 10, 2014 at 11:16 am

    Hi Elizabeth, yes there are others that can cause similar problems, primarily citral-rich oils such as lemongrass, and eugenol-rich oils such as clove and cinnamon leaf. Along with cinnamon bark, these are the main ones.

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