Sorry, dear Atlantic: essential oils are probably not “the new antibiotics”

I feel like there’s a lot of hype about essential oils and herbs in popular culture today — check out the herbal aisle at Whole Paycheck sometime for example. They get advertised as possible cures for all kinds of disorders, often on the basis of rather thin evidence. Take, for example, this article in The Atlantic about essential oils from last week that cropped up in my facebook feed. I figured I’d blog about it, not just because it bothered me (hey, who cares) but because I think it illustrates something interesting, particularly if you don’t work in medicine and don’t spend a lot of time thinking about what properties make a molecule into a useful drug. (I mean, come on. Who doesn’t spend all their time thinking about that kind of stuff?)

The author of this article makes three main arguments. First, she claims that adding essential oils from herbs (e.g. oregano oil) to animal feed could help keep farm animals healthy and presents some evidence to back that up (farmers who are doing this now etc). I don’t know enough about chicken farming to know how practical this is, although anything that would reduce antibiotic use in agriculture is great so far as I’m concerned, because there’s evidence to suggest antibiotic use in farming accelerates the emergence of antibiotic resistant bugs in humans. So this part was interesting and it’s what got me to read the article in the first place, although again, I can’t really comment on how practical it might be.

Second, the author argues that some of these essential oils — specifically tea tree oil — make good antiseptics so they’d be useful in hand sanitizers. And yeah, tea tree oil is used as an antiseptic in various personal care products already, so I can’t really disagree with that.

Finally, the author argues that because oregano oil and certain other essential oils kill bacteria in a petri dish, you might be able to treat infections with them in humans and animals. She claims this needs and deserves more investigation but the pharma industry isn’t interested because there’s not enough money in it, and hence these “new antibiotics” have so far been ignored, although new research is turning all this around. It’s this third claim that doesn’t make sense to me.

First point I want to make: chemicals from these essential oils are already used in many consumer products. Thymol is one of the two main chemicals that make up oregano oil, for example, and it’s a common ingredient in supermarket-brand mouthwashes like the one I use. But the properties you need in a mouthwash and in a drug are not the same. And in fact, the available evidence (even some of the evidence cited in the article) suggests it’s unlikely that chemicals like the thymol and carvacrol in oregano oil would make useful antibiotic drugs. The reason why is sort of interesting, because it illustrates what kinds of properties make a molecule useful as a drug. So let me explain. And as always I’ll keep this pretty simple because that’s what I (try to) do.

——–

If you’ve read this blog before, you’ve heard me say it a million times but I’m going to keep saying it again and again. Everything is toxic; the only difference is that some things are toxic at a much lower dose. And that’s not just true for humans. It’s also true for bacteria in a petri dish. You can kill them with salt if you dump enough of it in there. But that doesn’t mean salt is a useful antibiotic: the dose of salt it would take to kill the bacteria causing your UTI is very similar to the dose of salt it would take to kill you.

Likewise bleach. In a petri dish, bleach is one of the most effective bug-killers known to humankind. It kills any and every bacteria that’s ever been discovered, reliably and efficiently. And it kills bacteria at a much lower dose than say salt for example. So why don’t we use bleach as an antibiotic? Because the dose of bleach that would kill the bacteria causing your UTI is very similar to the dose it would take to kill you.

You get the idea. For something to be an antibiotic, the dose that will kill the bugs has to be much smaller than the dose that will kill you. That’s why bleach and salt won’t work. But how can we find chemicals that will?

If you want to figure out whether a chemical could be an antibiotic, start with these two questions.

1) What concentration of the chemical does it take to stop a given strain of bacteria from growing? This concentration is called the MIC (minimum inhibitory concentration) in pharma-speak, and it’s usually measured in micrograms of drug per milliliter of broth (or blood or whatever the bugs are growing in) although that’s basically the same thing as ppm and more people are used to thinking in terms of ppm so that’s what I’ll use here.

2) Could we give you a dose that would cause concentrations of this chemical in your bloodstream to stay above MIC for a reasonable length of time without causing toxic side effects? In other words, how much of the chemical do we have to pour into you to reach the MIC in your bloodstream and is that enough to harm you?

Remember, the key thing here: the chemical has to be much more toxic to the bacteria than it is to you, and it has to stay in your body long enough that bloodstream concentrations will stay above the MIC for a reasonable length of time. (There’s lots of details that go into determining whether it’s going to meet these criteria — how well the drug dissolves in water, how the drug is metabolized, etc. etc. — but these are the big picture questions).

So let’s ask these questions about the two main active ingredients in oregano oil, a pair of chemicals called carvacrol and thymol. Structures below. They look sort of similar, right? The only difference is in where the OH is attached to the ring.

ThymolCarvacrol

Now if you think back to previous posts, you’ll remember that groups like OH or NH2 with a “selfish” atom like nitrogen or oxygen increase water solubility. Having a charge (either plus or minus) somewhere on the molecule increases water solubility even more. These molecules, however, are mostly greasy, water-unfriendly hydrocarbon with just one OH group and that OH is nowhere near acidic enough for the molecule to have a charge anywhere near pH 7.5. So these molecules have very low water solubility, and that’s why oregano oil doesn’t mix well with water. This is something I’ll come back to in a minute. For now, though, let’s figure out whether these could be good antibiotics by thinking about our two questions, starting with what are the MICs (concentration it takes to make bugs stop growing).

You can measure MICs in a petri dish or a well plate; there’s several different ways to do it, all of them reasonably straightforward. One way is the E-test test like in this picture. You place a premanufactured strip containing preset concentrations of the antibiotic into a petri dish with the bacteria then check the dish after a preset amount of time and you’ll see something like the picture below. The # marked on the strip tells you what the concentration of the antibiotic is at that point, so that’s the concentration it takes to stop this particular strain from growing. (There are other techniques that are better for most purposes, but this I feel like this one is easiest to explain so that’s why I’m using it for an example.) The #s on the strip in the picture are in ug/mL or ppm just so you know. With MICs lower is always better (the lower the concentration of the antibiotic required to stop the bugs from growing the more potent it is.)

So how do thymol and carvacrol from oregano oil measure up? Not well, I’m afraid. I skimmed through a few of the papers I found on PubMed for these chemicals (there’s not a lot of research on them out there but there are some published papers) and while you can bet there’s some variation between labs and studies and techniques and so forth, from what I can find, the MICs for thymol and carvacrol against the strains that have been tested are very high. They’re very weak antibiotics.

Just to take one example, see this paper from 2001, a collaboration between academic researchers and a couple of scientists at Unilever, a company that makes a lot of the consumer products in your supermarket (detergent, soap, cosmetics, mouthwash, deodorant, etc. etc.) They tested carvacrol and thymol against an MRSA strain and got MICs of about 175 and 140 ppm respectively. To give you an idea how weak that is, consider that if a staph strain has an MIC for the drug vancomycin of 16 ppm or above, it’s said to be vancomycin-resistant.

And it gets worse. Oregano oil had an MIC of 575 ppm — probably because a substantial fraction of the oil is other chemicals that have even less activity than thymol or carvacrol. The data from this paper suggests the effects of thymol and carvacrol are additive, not synergistic, meaning that 100 ppm thymol plus 100 ppm carvacrol has about the same effect as 200 ppm of either.

But let’s try another study. This Italian study in 2004 found MICs against various staph strains of roughly 150 ppm and up. Or let’s even take one of the papers the Atlantic article linked to, this one about basil and rosemary oil. The MICs for those oils are measured in microliters per milliliter, which is parts per thousand, and they’re so high (for an MIC) when I saw them I was initially a little worried they might have been misprints.

Now these kinds of MICs are OK for a preservative or a mouthwash additive or an antiseptic; you can easily put together a product that will include thymol or carvacrol at those kinds of concentrations. My mouthwash has close to 640 ppm thymol for example in ~20% alcohol (that alcohol will help dissolve the thymol, which doesn’t dissolve well in pure water, plus at 20% alcohol’s pretty good at killing bacteria too). But if I want to use thymol or carvacrol as an antibiotic, I’m going to need to give you enough that the concentration of thymol in your blood will reach those MICs and stay above those MICs for a reasonable length of time. That’s a very high bloodstream concentration of drug to maintain, especially given that it seems your liver rapidly metabolizes these chemicals and your kidney is also filtering them steadily from your bloodstream. On top of that, these chemicals are very fat-soluble so they should quickly diffuse out of your bloodstream into your tissues (the pharma-speak jargon is high volume of distribution). Put all this together and I’d bet you my lunch the doses you’d need to reach those kinds of bloodstream concentrations are probably either worrisome or unreasonable.

Does this mean that thymol and carvacrol definitely could not work as drugs? No, I’d need more data to prove that. In particular, I’d need more complete data on how rapidly your body eliminates them (through metabolism and excretion) and MICs for more strains would be nice. And I should also point out that I just wandered through PubMed and quickly skimmed through a few papers at random here, so I don’t claim this is a full survey of the literature. But just a quick look at the available data suggests it’s unlikely these are good candidates for further investigation, at least as antibiotics. They could certainly work as preservatives or antiseptics, and the article presents some interesting data on their possible use in animal feed to help keep chickens healthy, but as antibiotics to cure an infection, well…I don’t know how that’s going to work. Moreover, most of the data I linked to above has been out there for years. It’s not new at all.

So why does this Atlantic article argue these could be “The New Antibiotics”? I think probably the folks at the Atlantic saw some papers and/or press releases claiming that “Essential Oil X Can Kill Bacteria in a Petri Dish!” and didn’t realize how little that means by itself. When you say a chemical can kill bacteria or cancer cells in a petri dish, the first question you should ask is at what concentration? because anything can kill bacteria in a petri dish if you dump enough of it in there, but it’s a question of what concentration it takes, you know. Next, you should ask is that a concentration I can reach in your bloodstream with a reasonable dose and without causing toxic side effects? because that’s what separates the drugs from the other stuff.

The other (faintly) odd thing to me about this is the end of the article. The author says that essential oils need more research because, and I quote, “they should be given the same kind of scrutiny that antibiotics haven’t been.” And this part is just simply not true. Any drug has to get approved by FDA before doctors can start prescribing it. And FDA requires reams of clinical trial data (not to mention preclinical) before they’ll approve your drug, and that data has to make sense. Extensive scrutiny is what every drug receives — has to receive — before it’s approved. So that last part makes absolutely no sense to me.

19 thoughts on “Sorry, dear Atlantic: essential oils are probably not “the new antibiotics”

  1. I honestly don’t remember when I signed up for your blog but I’m really glad that I did. This was a great post!

    Out of curiosity, do you know if fresh garlic’s reputation as a killer antibiotic and antifungal agent is deserved? It’s always the first thing I turn to when sick and now I’m wondering if I’m just an idiot!

    • Thanks. That’s a good question. The simple answer would be I don’t know…but I know how I would try to figure out.

      If you want to look up what data is available on a given drug/chemical/extract, you can search at PubMed. It’s a database of all published scientific articles that relate to biology, medicine and biochemistry. Google Scholar works too and is also free to access. Unfortunately many science journal publishers still charge for access to their articles — personally I think that’s a little odd given that much of the research they publish was publicly-funded — so not all of the articles on PubMed/Google Scholar are free to access (if you stop by a university library, however, you can usually access these kinds of articles, because most large universities have subscriptions). Also, these are of course articles written by researchers and doctors for researchers and doctors, so they’re written in med-speak and assume a certain amount of background knowledge of medicine & biochemistry you may or may not have. For me, though, this is where I would go to find what kind of data is available on something like, say, garlic and health, because I always prefer to go find the original data when I can.

      If you just want to get a layperson-friendly summary without digging through zillions of references on PubMed, a good place to go is NIH MedlinePlus, which is maintained by National Institutes of Health. This is their page on garlic:

      http://www.nlm.nih.gov/medlineplus/druginfo/natural/300.html

  2. The recurrent meme “Kills 99.9% of bacteria” keeps showing up in advertising, and it takes a bit of thought to figure out why it’s likely not useful. My favorite example is in mouthwashes. They claim that their product “kills the bacteria that cause bad breath,” but what they don’t say is that the experiment is done in vitro. They carefully never claim that your mouth is cleansed of odor-causing bacteria. Your breath smells good (for a while) because of the scented additives in the mouth wash.

    Nice job Puff! Glad you’re back.

  3. An important feature of traditional antibiotics is that they are highly specific, whereas most essential oils appear to exert their effect through their general properties (volatile and lipophilic)–plenty of exceptions of course. Good antibiotics work by inhibiting some essential cellular process in bacteria like translation, transcription, or replication, and it is their chemical structure that gives them a high affinity for the active site of an enzyme. Sort of like a monkey wrench tossed into the gears of a motor. Essential oils, on the other hand, probably work as general membrane disruptors (Bakkali 2008 Food & Chem Tox). Since we and bacteria have similar plasma membranes in our cells, they aren’t very specific for their targets. The best antibiotics exploit the differences between bacteria and humans, such as different ribosome types or biochemical pathways present in one and not the other (bacterial isoprenoids are made through the MEP pathway–absent in humans). Finally, thymol and carvacrol may not even be the best anti-bacterial essential oils. Beta-caryophyllene may be more potent against some kinds of bacteria (Huang et al. 2012 New Phytol), but this is probably of more benefit to protecting plants from bacteria than humans. However, since food poisoning is usually due to bacterial contamination of food, essential oils may still be of considerable value in reducing food borne illnesses, assuming genetic engineering one day gains broad consumer acceptance. (Key words for the curious: terpene synthases, fosmidomycin, statins, plant volatiles, nerolidol, (E)-beta-farnesene)

    Great post by the way. Keep it up!

    • Thanks. Like you say thymol and carvacrol are believed to exert their antimicrobial effect primarily through membrane disruption, which is not the most terribly specific or selective mechanism of action you could think of. The polymyxin antibiotics (colistin, polymyxin B) are potent and work through membrane disruption but they’re fairly toxic to the patient and have some nasty side effects. Doctors tend to use them as a “weapon of last resort” against gram-negative bacteria. Unfortunately with the emergence of more antibiotic resistant gram-negs from what I’ve heard I believe doctors have been having to use them more often.

  4. Thank you for this. I went to an essential oils “class” run by a Doterra sales person the other day. She made a number of crazy claims about the products she peddles.

    One thing was about skin, particularly the soles of the feet, absorbing the oil into the bloodstream and having some sort of effect. Is there any evidence for this?

    • Well, sure, I imagine some fraction of the thymol or carvacrol in the oil is absorbed through your skin, but again, the question is at what rate and how much and would that be enough to hit the bloodstream concentrations you would require for this to act as an antibiotic without causing toxic side effects. I suspect your Doterra sales rep doesn’t have the answers to those questions — but is going to keep pushing this as a “natural antimicrobial” anyway

  5. As regards:

    “On top of that, these chemicals are very fat-soluble so they should quickly diffuse out of your bloodstream into your tissues”

    In this case, that seems like a good thing: if you have the usual sort of bacterial infection, most of the bacteria are going to be in your tissues, rather than in your bloodstream.

  6. I agree with you, essential oils are probably not viable replacements for antibiotics however I still think that more research relating to essential oils should be preformed ( Although I’m probably completely incorrect since I am biased on this matter due to the fact that I’ve been part of a team that have recently had a paper published (Nothing groundbreaking though) and that I’m currently performing research in this area.). I think the reason I believe this is that the essential oils are rather picky in what they want to kill, for example tea tree oil (I can’t remember what component is effective against e.coli) is extremely effective on e.coli even though it’s completely unaffected on MRSA. Anyways what I’m saying is that we shouldn’t dismiss essential oils so quickly, even though essential oils will probably be useless in the ‘real world’.

  7. I think people as well as european countries, who heavily use essential oils, are saying that the essential oil ITSELF does the healing in terms of disease and ailments. It is not necessary to turn it into a “drug” as you mentioned…that would probably be counterproductive.

  8. I would suggest you re-visit your research. Also I would suggest you spend some time getting a degree (at least) in microbiology or pharmacology. Any of these suggestions would be better then you spending your time slandering the efforts of those trying to come up with a solution that medicine has failed to deliver.

    • Currently doing research in this area, and alot of the information in the article is misrepresented and the author really hasn’t surveyed the literature at all.

      Also to echo the point of another reader who said “Also, oregano essential oil is made up of hundreds or probably thousands of phyto-chemicals, less than a handful of which have been researched. While you can try to break down and copy one component to market in other products, essential oils offer much more than one isolated component.”

      This is somewhat true and a completely valid point.

      Also what you said about MICs and dosing is just plain wrong.(I’ve been working on dosing and EO MICS for the past year.)

      If I were you I’d go through the literature again.

  9. There is also a meme in research where you just try 100 different harmless things, and see which ones may work. So like: you take someone with hay fever, and give them aspirin. Does it help? Maybe it does. Then figure out why. I call it the “throw it against the all and see what sticks” protocol. Kind of random, but sometimes it works.

    So I tried this with Oregano oil. I had a skin condition. Cellulitis, nasty stuff, as a result of a hospitilization and lots of IVs. Big lumps under the skin where the IV’s went in. I was prescribed an oral antibiotic to help: which it did. But as an experiment, I also took some fairly generic skin cream, added varying amounts of oregano oil, to one arm. But the arm with the ad-hoc cream went away about as twice as fast, much to my surprise! It also eased the pain rather immediately, which I liked.

    So here is the thing. I don’t know, in theory, if Oregano oil works on cellulitis. Or if it works in the lab. I do know that my ad-hoc mix DID work, or at least make the antibiotic work better. I’ve used it after the oral antibiotics ran out, and my skin just got better and better. What did it DO? I dunno. I do know it doesn’t make me sick, doesn’t cost much, and makes my skin healthier than it has been in years.

    The thing is: the fact you can’t PROVE something works, doesn’t mean it doesn’t work. If people can experiment, they will. If it works, they will tell other people, and they will experiment. That’s how science got invented.

    Later on someone will do the science to figure out why, say, quinine kills malaria or bread mold kills bacteria. For now though, the people who say “bread mold kills infections” turned out to be correct. I expect Oregano oil will prove to be one of those things that works too, even if we don’t know why.

  10. I would strongly disagree that the FDA can effectively evaluate drugs based on the research provided by the company trying to get their drug approved. They don’t conduct their own research anymore and rely only on the information provided them, which we’ve seen time and again is an issue. Pharmaceutical companies effectively largely fund the FDA, so you can’t say we can rely on the FDA’s approval to determine if a drug has truly received “extensive scrutiny.” Check out Overdosed America for well-researched/cited info about this topic, or start here: http://www.pbs.org/wgbh/pages/frontline/shows/prescription/hazard/independent.html, and dig around.

    Also, oregano essential oil is made up of hundreds or probably thousands of phyto-chemicals, less than a handful of which have been researched. While you can try to break down and copy one component to market in other products, essential oils offer much more than one isolated component. We still have only begun to scratch the surface of the research to understand how it works, but do your own research–test its efficacy on yourself.

  11. Essential oils can smell nice, but they’re hardly treatments for illness. When the dose makes the poison, a few drops of this and a few drops of that in some neutral carrier oil couldn’t poison a fly. It’s almost getting into homeopathy territory.

  12. I’m well on my way to recovering from infections of Borrelia, Bartonella, mycoplasma, and anaplasma. Essential oils of clove and oregano have played a huge part in this.

    • I did a semi-scientific test on this. I had some infections on both my arms. I was in the hospital for a week and they had made multiple IV’s. At each IV site, I got a huge welt, which the doc decided was cellulitis. So he put me on antibiotics to clear up the welts.
      Now, that DID start clearing them up, but they hurt. So on one arm I also used a homemade ointment where I mixed emu oil, tea tree oil, oil of oregano. On the other arm, I did nothing.
      The oral antibiotics worked on both arms. However, the welts with the herbs healed up within maybe 2 days, while the antibiotics-only took about 2 weeks. Also, both arms were quite swollen, but the swelling on the arm with the herbal oils shrunk much faster.
      At this point, when I get what is clearly any “skin” condition, I go for the ointment first. Let’s call it “first do no harm”. In favor of herbal oils you have:
      1. It is very highly unlikely to kill you. Or even make you nauseous.
      2. It doesn’t cost much.
      3. It doesn’t cause antibiotic resistance.
      4. It smells good.
      5. In real life, it works for a lot of people.
      So what if it doesn’t work in a petri dish? If it works on MY arm, there could be all kinds of reasons (and yep, mindset could be one of them).
      But there is another issue. Lately I’ve been going to the doc for what is clearly a bacterial infection (fever, high WBC) and the DOCTORS are having a backlash against antibiotics. “well, we don’t want to give you these because of clostridium!”. I’m not saying they are wrong (although really, we’ve been through clostridium and it’s not that hard to fight). Point is, I need something *I* can fight infections without relying on a prescription. Herbal oils do it. So does infrared heat, and topical iodine (be careful with both: they can cause burns).

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