Essential oils and gut flora

In a blog post dated July 13th 2014, Madhupa Maypop quoted Paul Bergner, saying: “The scent of an essential oil can kill gut flora just like antibiotics do, according to Paul Bergner, director of the clinical studies program at the Rocky Mountain Center for Botanical Studies. He told me that breathing the oils puts them into the blood stream very quickly and can be a major disturber of intestinal health and contributor to poor immune functioning.” However this quote has now been removed from the post, since Paul Bergner has denied that he ever said this. Paul contacted me directly on July 15th, saying: “I have never said, or even thought, that inhaled essential oils could have any effect on the gut flora. There may be a theoretical concern about taking undiluted oils internally, but this has never been demonstrated.” The original Paul Bergner quote in fact comes from Susun Weed’s website. Paul has asked Susun to remove the misquote from her site.

It is true that inhalation of essential oils results in most constituents getting into the bloodstream (it’s not correct to speak of “essential oils” in the blood, since individual constituents are not equally absorbed). The same is true of any mode of application, though generally the amounts in the blood are in the range of 1-100 nanograms per mL of blood – quite low concentrations. Whether these constituents might then negatively affect the bowel flora is pure speculation.

Fit and slim female model exposing her belly and waist

We do know that enterically-coated capsules of peppermint oil are beneficial in cases of irritable bowel disease and that these capsules result in a (substantial) peak serum concentration of 1,492 ng/mL for menthol. We also know from this report that peppermint essential oil had a beneficial effect on the balance of gut bacteria in a case of SIBO (small intestine bacterial overgrowth).

It would be useful to know more about particular oils, doses, routes of administration and their effect on the body’s microbiome. But in the meantime, it is rash to assume that essential oils negatively affect the balance of bowel flora, because there is no clinical evidence that this happens. On the other hand, decades of clinical experience by doctors in France suggests that essential oils frequently heal both acute and chronic infections without the damaging, and often long-lasting effect on bowel flora that comes from the use of antibiotics.


By |2018-04-24T20:25:46+00:00July 14th, 2014|Aromatherapy / Research, Myth-busting|22 Comments

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  1. Dawnmarie Schneider July 15, 2014 at 6:41 am

    Thank you for addressing this issue. I was wondering about this point.

  2. Sylla July 15, 2014 at 6:49 am

    Paul when asked has denied saying that so it goes back to Susan Weed, herbalist who hates essential oils and thinks they are unsustainable….

  3. kelly Dolan July 15, 2014 at 6:58 am

    Thank you for clarification!! It is very troublesome when someone makes alarmist statements with no evidentiary back up. This blog post has been linked and re-linked all over Facebook.

  4. J Ribbe July 15, 2014 at 9:11 am

    Thank you for addressing this question — I just saw that article and was wondering about that portion. One further question, though: I’ve been very concerned about the recommendations for taking essential oils internally that I’m seeing more and more, especially from sales representatives for multi-level marketing companies (“add a few drops to your water …”). Could that be damaging to intestinal flora?

  5. Pat Robinson July 15, 2014 at 9:26 am

    EO effect on intestinal cells:

    EO effect on (mouse) embryos:

    EO effect on (chick) gut microbials:

    EO effect on (early weaned pig) gut microbials:

    EO effect on (pig) gut microbials:

    EO effect on (rabbit) gut microbials:

    EO effect on (pig) gut microbials (Conclusion, page 106.):


  6. Lindsay Wilson July 15, 2014 at 9:52 am

    Hi there Robert,

    I have since heard from Paul Bergner that he was misquoted in my article (due to the fact that the source I originally pulled the quote from had misquoted him) and have removed this misquote from my article. In my article I actually link to your 2nd edition of Essential Oil Safety and find it to be a good and reliable resource.

    The main point of my article is to high-light the overuse and abuse of essential oils. I do sense that essential oils, used in both a specific, strategic and skillful way can be very healing for people.

    Be well, Lindsay Wilson

  7. Ann Wooledge July 15, 2014 at 10:59 am

    Thank you Robert for writing this. I have been reading some herbal texts about herbs being antibiotics and kill only the harmful bacteria. Also in many aromatherapy books (the good ones, not the fluff ones), it is stated that essential oils do not kill good bacteria. That being said, I can personally tell you that my husband had a very deadly and extreme overgrowth of Candida back in Nov. 2011. We fought this using essential oils and chose not to take the steroids (really!?) that the dermatologists wanted him to take – which would, of course, have fed the Candida. So we were able to eliminate over the period of about six months this yeast overgrowth using essential oils – which shows me quite clearly that these essential oils did not affect the good bacteria balance but enhanced their balance. He took no other medications other than a fungicidal at the very beginning of this very scary experience and then for only a week. The book I’m reading right now – Herbal Antibiotics – goes into some detail about why plant-based medicines do not affect the good gut flora. I would assume that we could extrapolate that belief to natural essential oils as well.

  8. Kelly Ann Taylor July 15, 2014 at 3:20 pm

    Dr. Robert…I am so glad that you published this article. In my novice way of thinking…an antibiotic is an antibiotic. Whether it be nature’s antibiotics or Big Pharma, to me it does not make a difference if the action upon the subject be the same. I have been wanting to ask you about this for some time now, as I have many many friends to drop essential oils into gelatin capsules and take them when sick up to several times per day. After all the discussion is said and done, if there is no disruption of gut flora per se, then why are you against internal usage for the casual user and non medically qualified individuals? Because if it is not killing off good bacterium and flora, what other harms does it have?

  9. robert July 15, 2014 at 7:38 pm

    Thank you Pat Robinson,

    I will make a brief comment on each of your citations:

    EO effect on intestinal cells:
    This paper is about cytotoxicity, and is not relevant to the issue of gut flora.

    EO effect on (mouse) embryos:
    An important paper on toxicity and pregnancy, but not relevant to the gut flora issue.

    EO effect on (chick) gut microbials:
    If you can understand this paper, please explain it to me! And, “essential oil blends” were purportedly used, but no essential oils are mentioned.

    EO effect on (early weaned pig) gut microbials:
    This paper is not about essential oils, it is about essential oil constituents – carvacrol and cinnamaldehyde. Of 21 P-values cited, only one is significant, even from the high doses used.
    Also not about any essential oil. From a diet supplemented with 0.03% plant extract mixture, (including carvacrol and cinnamaldehyde) for 3 weeks, there was no reduction in the number of total bacteria, but some changes in ecologic structure and metabolic activity were noted.

    EO effect on (pig) gut microbials:
    This is not about an essential oil, it’s about thymol. Dietary supplementation with 1% thymol (for 5 days?) caused “clear changes in the small intestine microbacterial community”

    EO effect on (rabbit) gut microbials:
    Dietary supplementation with thyme oil (0.5 g per kg of food) had a positive effect on intestinal health.

    EO effect on (pig) gut microbials (Conclusion, page 106.):
    This is a 286 page thesis, with many citations. The conclusion refers to essential oil constituents, saying that they have the potential to “modulate the flora and fermentation pattern in the gastro-intestinal tract of pigs.” This is not presented as a negative. In another summary comment (p70) it is stated that “in none of these studies the total number of bacteria in the gastro-intestinal tract was reduced.”

  10. robert July 15, 2014 at 7:49 pm


    Essential oils are antimicrobial, but are not antibiotics. While this may seem merely semantics, there are significant differences. Until relatively recently, all bacteria were viewed as potentially harmful, and certainly not beneficial, though now we are starting to appreciate the long-term harm that antibiotic use can do, whether through animal farming, or over-use, even regular use, in disease treatment. You say that I am “against internal usage for the casual user” though this is not totally true. I do not believe that non-practitioners should prescribe/recommend oral use of EOs or others, and I am wary of scenarios involving the liberal oral use of EOs for people who are not sick. But I am not, and have never been, against sensible self-treatment using EOs orally, for a limited period of time.

    • Kristin March 22, 2016 at 5:42 pm


      Thank you so much for patiently clarifying issues so well. I continue to study your book on safety and continue to research the studies referenced, results and more. It was initially so difficult to find resources such as yours and Dr. Buckle’s Clinical Aromatherapy resources. I am fascinated by all of the possibilities but have a sincere concern for safety. Thank you again for your work. As a nurse I have seen how complicated it can be to cure but then have to deal with the undesired side effects. It is a fascinating field and very timely.

  11. Susan Burch July 17, 2014 at 6:24 am

    Hello Robert.

    I have IBS (mild) and would like to know what i should be looking for when buying peppermint oil capsules? I was taking Florea but they did not agree with me so I am searching.

    Thank you 🙂

  12. robert July 17, 2014 at 8:00 pm

    Hi Susan, I don’t know Florea, but you need enterically coated capsules such as Colpermin, Mintec, or Heather’s Tummy Tamers.

  13. tim blakley July 22, 2014 at 11:10 am

    Paul is an excellent and knowledgeable clinical herbalist who has done much over the years to further the use of medicinal herbs. I also have always enjoyed hanging out with Paul at conferences. However, at the Breitenbush Herbal Conference last year Paul did say something similar to what was reported, unfortunately I cannot quote it as it was nearly a year ago. A co-worker also heard it in his presentation and it had to do with smelling Rosemary essential oil and somehow that it just about knocked him out and was too strong to use. In that presentation Paul was clearly not a fan of essential oils and I was somewhat surprised. We all have our preferences and for some people smelling oils can be ‘overwhelming’ I guess. Personally, I’m an essential oil junkie and even though my song, ‘Aromatherapy Junkie’, played on the Ukulele, did not make it to the top of the Pop Charts, I continue to be an avid oil junkie.

  14. Susan Apito August 9, 2014 at 8:32 am

    You say “…decades of clinical experience by doctors in France suggests that essential oils frequently heal both acute and chronic infections without the damaging, and often long-lasting effect on bowel flora that comes from the use of antibiotics.”

    Carefully worded. And not the same as saying there is no damage to bowel flora at all, just not the effects we are currently familiar with from the use of antibiotics.

    I am confused by a comment, from the comments “Also in many aromatherapy books (the good ones, not the fluff ones), it is stated that essential oils do not kill good bacteria.”

    Do we really have a clear, hard line between good bacteria and bad bacteria? I don’t think so. Is Clostridium botulinum a good bacteria or a bad one? Because botulinum toxin can cause potentially fatal paralytic illness so “bad” – but it is thought to be a “good” bacteria when this same toxin is injected into people for medical or cosmetic purposes.

    What bacteria in the gut are responsible for some people being naturally thin and others suffering their whole lives with weight issues? The answer…we don’t know. Science suspects gut bacteria effect every metabolic process in our bodies, but they don’t know exactly which bacteria, or how or why or what drugs, foods or lifestyle choices determine who has the “good” bacteria and who does not. So how can we even guess that essential oils will have no effect and whether the bacteria that tip the balance one way or another are “good” or “bad”. Maybe the good bacteria make us fat, because fat people in certain life threatening situations are healthier. We just don’t know. So how does a person make an informed benefit vs risk assessment when so little is really known?

    Is “essential oils really only kill bad bacteria so feel free to take them internally, they can’t hurt” really what you want the *take away* from this post to be? Because that is what some people are reading, and repeating!

    Robert you write “But I am not, and have never been, against sensible self-treatment using EOs orally, for a limited period of time.” Most Qualified Aromatherapists will agree with you, however, I think as a leader in this industry you need to qualify what you mean by “sensible self-treatment” – because I can tell you from first hand experience with dozens and dozens of posts and emails and messages – that there are tens of thousands of salespeople and their customers out there, newly introduced to the wonderful world of essential oils, who honestly believe their internal use of essential oils is perfectly sensible, and in fact *better* than just “sensible” – they think it is safe under all circumstances; they view a limited time to be years not days; and they believe they are treating everything from diabetes to cancer, ADHD to EBOLA. So I think more specifics are necessary from you, as someone whose words are often taken out of context and used by multi-level-marketing salespeople in order to push internal use, undiluted use and medicinal use.

  15. Kelly Ann Taylor August 9, 2014 at 11:17 am

    That is extremely helpful information for me Robert, and thank you so much for your comprehensive reply!!! I will be reading every link and re-formulating my blanket reply to the endless list of customer who write to me. We all appreciate you very very much!

  16. robert August 9, 2014 at 12:36 pm

    Sue – I am not saying that there is no effect on bowel flora from the clinical use of essential oils, but I am saying that there is no evidence of a damaging effect (such as is seen from antibiotics), and that this seems very unlikely.

    I agree, the distinction between “good” and “bad” bacteria is unclear. Books have been written about this, such as Good Germs Bad Germs, Missing Microbes, and The Wild Life of Our Bodies. I would recommend all of these.

    It’s odd that you quote me, say that my words are often taken out of context, but you just did that. What I said in full was: “I do not believe that non-practitioners should prescribe/recommend oral use of EOs or others, and I am wary of scenarios involving the liberal oral use of EOs for people who are not sick. But I am not, and have never been, against sensible self-treatment using EOs orally, for a limited period of time.”

  17. n September 13, 2014 at 8:47 am

    i don’t like the mlm marketing for EO’s either. they can’t have it both ways. EO’s are either medicinal, in which case they should be taken as carefully as medicine, or they are just for flavor and aroma, then go ahead and add a couple of drops to your water just to suit your taste. but if it is medicine then best to use it as such. you wouldn’t add a couple of aspirin to your water for a flavor kick, or some alka seltzer just because you like the fizz. so don’t do it with therapeutic eo’s. use juice or extracts instead.

  18. Jenn September 23, 2014 at 8:38 am

    Hi Robert! Thank you for doing what you do. I am new to researching essential oils and from what I gather you are the man! 🙂 I will be reading everything I can from your site and hope to receive your book soon.
    Thanks again!

  19. kacie December 10, 2014 at 12:37 pm

    I really appreciate everyone’s input. I think lay persons try to get a “final answer” when EOs are not simple compounds and the body absorbs the different constituents in different %s. Tisserand brings up a lot of great points. When citing articles, many of the statistical reports are not done correctly. I had a class on interpreting statistics, so you have to look carefully. I think to truly understand the potential affects of EOs and their constituents, you need an understanding of chemistry esp organic and biochem. It is all interconnected, proteins, immune cells, gut flora, etc. There are so many more studies needed, which brings me to my next point… testing constituents on rats or other animals is not how the human body is or may respond. I take EOs orally when I am desperate for relief. I think in high enough doses (which we don’t know and probably depends on the % of gut flora species thus ratios) could EO constituents affect the health of proper digestion functions. In order to balance my use of EOs, I eat a balanced diet, ensure that I get my vitamins, minerals and I also drink Kefir. Excess microbes end up in my septic tank:) I personally think high enough doses over a certain prolonged period of time can affect or reduce your bowel flora. Let me give you an example…

    I took DDR capsules from doTerra. After a few months, I ended up with a urinary tract infection. I do not have intercourse and I do not use personal feminine hygiene products around there. I don’t eat sugar. Wondering the cause of my UTI, I researched how the digestive system affects the urinary tract, and felt there may have been a direct correlation. So, I stopped the DDR capsules, unfortunately had to take antibiotics, and then followed up with drinking kefir. All better now.

    However, the other day, I felt great, then ate out and ended up with a foodborne illness. Out of desperation, I took a few drops of essential oil + carrier oil I had on hand orally and followed it down with a few sips of water. After a few minutes, my sensation to vomit dissipated. It came back so I took a few more drops of EO, and about an hour later, I felt like I was going to live. I was so glad I had my EO blend on hand.

  20. Earl Martin March 11, 2015 at 1:42 pm

    Hi Robert, Thanks for sticking to the facts and leaving emotions and hearsay out of the discussion. As an MLM’er who uses and promotes the use of essential oils, and as a certified aromatherapist, I do get frustrated with misinformation about the use of EO’s. But this is not specific to this industry. Every industry has misinformation, including mainstream medicine. If everyone studied the effects of medically prescribed drugs the way many people study the effects of EO’s, the drug companies would be in trouble. There are so few incidences of harmful use of EO’s vs. prescription drugs that it’s sad to see how much backlash the EO’s receive from people that actually like EO’s. According to the US Center for disease control:

    “Deaths from drug overdose have been rising steadily over the past two decades and have become the leading cause of injury death in the United States. Every day in the United States, 120 people die as a result of drug overdose, and another 6,748 are treated in emergency departments (ED) for the misuse or abuse of drugs. Nearly 9 out of 10 poisoning deaths are caused by drugs.”

    In an article written by an herbal tea salesman, she writes:
    “It is no secret that some of these [essential] oils can kill you.”
    even though she quotes Robert’s article in which he states
    “As used in aromatherapy today, essential oils have not caused a single death.” She also quotes an article that says Tea Tree oil is poisonous because someone who ingested 1/2 Cup of it got sick. If someone took a 1/2 cup of Robitussin and got sick would they say it’s poisonous?

    And I would like to see someone come up with any statistic from a government or trusted medical website that states the real dangers or health risks of EO’s. I can only find warnings by the FDA about not stating that EO’s can treat or cure disease. Nothing about them being harmful or fatal. From the National Cancer Institute: “Safety testing on essential oils shows very few bad side effects or risks when they are used as directed.”

    Drink a 15ml bottle of pretty much any EO and you’re not going to feel very good. Eat 20 Tylenol and you have a good chance of liver failure.

    I know this is a discussion of gut health, but my point is about being smart. Dosages are critical, no matter what you take. Treat EO’s with respect and educate yourselves and others. If you see people abusing the use of oils, help educate them, don’t condemn EO’s or MLM companies that sell them.

    Thanks again Robert for your dedication to education and reason.

  21. robert March 26, 2015 at 5:14 pm

    Thank you for your comments Earl. For much detail on the safety issue, see my book And for more on the dynamics between conventional medicine and essential oils, see

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