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Why Is Essential Oil Dilution Important?

dilutionHi Robert,
I’m having some trouble understanding my essential oil dilution research and was hoping you could clarify for me.

1.) Why is dilution so important if 95% of the oil evaporates when applying topically?

2.) Is dilution recommended due to sensitivities that could occur? I have used oils neat before and never had an issue.

Thank you for your time,

Hi Danielle,

It partly depends on why you are applying essential oils, and why to the skin. Much of my teaching is about cosmeceutical effects and products for skin care. Dilutions of essential oils are generally more effective in this area, because the skin does not respond well to concentrated EOs. They are drying, the risk of adverse reactions is increased significantly, and for skin care/personal care you simply do not need more than 1-5% essential oil.

About 5% of applied EO is absorbed into the body through the skin, but more if undiluted oils are used. When you first apply an EO to the skin, 100% of it is there for a while. This is when any adverse skin reaction will occur, so while it is true that most of it evaporates with time, this is not as relevant as the initial dilution.

Essential oil dilution is important for two safety reasons. One, to avoid skin reactions: irritation, sensitization and phototoxicity. Two, to avoid systemic toxicity, such as fetotoxicity, hepatotoxicity, carcinogenicity and neurotoxicity. Adverse skin reactions are obvious when they happen, but systemic toxicities may not be. Skin reactions are totally dilution-dependent, and safety guidelines exist to minimize risk. This does not mean of course that every time a person uses an undiluted oil there will be an adverse reaction. Many times there won’t. But more is not always better, and minimizing risk is generally a good idea. A phototoxic reaction for example, can be very, very nasty.

If you want to know more about what can go wrong and why, I would recommend my book Essential Oil Safety 2e.


By | 2014-05-09T14:15:15+00:00 May 9th, 2014|Q & A|13 Comments

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  1. Karen Uhlman May 12, 2014 at 8:26 am

    Hello Mr. Tisserand, I was hoping you could help me with a question. I have a potential customer who would like to use essential oils for Emotional Freedom Technique (EFT). If she dilutes the oils, would that lessen their effectiveness? Does it change the megahertz? Thank you.

  2. robert May 21, 2014 at 8:25 am

    Hi Karen, I am not familiar with EFT, and cannot comment on dilution and effectiveness, but I would assume that any vibrational frequency is not changed by dilution.

  3. Daniel May 28, 2014 at 4:24 am

    Dear Robert,
    Regarding dosage for bathing, I have seen a video of a famous aromatherapist from Belgium recommending dilutions of 15 to 25 drops of essential oils for a bath. On my course (in London) and in some of the books from British authors the recommended dose is between 6 and 12 drops. I personally found that 6 drops is very mild and the fragrance only barely notice noticeable.
    Would you be able to explain such difference and tell us what your thoughts on safety this might imply?
    Many thanks

  4. Andrew May 29, 2014 at 1:27 pm

    I’m interested to know how you came to these conclusions about dilution, because they don’t really fit with what (admittedly little) I know about pharmacological/toxicological principles.

    According to classical toxicology, “the dose makes the poison.”

    Thus, if you were to put a certain amount of an EO on your skin neat, and then diluted, it should make no difference unless the carrier oil significantly impedes absorption.

    I can only see two ways that they would impede absorption in any significant way. One, they could speed evaporation, which is clearly not the case. Two, they could bind the oils chemically, which would presumably denature the oils.

    I suspect, however, that carrier oils act as a suspension medium for the essential oils, and thus do no more than space the molecules out. In this case, the systemic dosing would be the same for a neat oil or a diluted oil.

    In fact, if the carrier oil impedes evaporation of the oil, then the total absorbed dose would be higher with a diluted oil.

    But perhaps you have some experimental evidence showing differential absorption rates…

  5. robert June 4, 2014 at 8:47 am

    Hi Andrew, you are absolutely right, for systemic toxicity what matters is the total amount (dose) of essential oil that gets into the body. So whether you have a 10% dilution or a 1% dilution makes no difference, so long as you apply 10 times more of the 1% dilution than the 10% dilution. But applying 10 times more in practice is probably not feasible. Greater dilutions do reduce the total dose of essential oil proportionately, so long as the total amount of blend applied remains the same. Comparing transdermal absorption of an undiluted EO to a diluted one, there is a greater % absorbed from the undiluted oil, so we could deduce from this that a carrier oil slightly impedes absorption.

  6. robert June 4, 2014 at 9:42 am

    Daniel, it does depend on which oils are being used, and whether they are mixed in something that will help them dissolved in the water. If you want to take the risk of sitting on 5 or 10 drops of undiluted peppermint oil as you get into the bath, be my guest, and do report back!

  7. Leslie November 6, 2014 at 10:15 am

    I will attest to the fact that very little concentrated oil goes a long way! I made a ‘repellent’ that consisited of aloe juice, water and a total of maybe 18 drops of 3 different oils-Lemongrass included. I am now finishing up a does of Prednisone, as my arms and legs broke out in a rash that continued for over a week! Lesson learned!

  8. Angela Quirie January 23, 2015 at 1:44 pm

    I am currently reading a book by Patricia Davis – Subtle Aromatherapy and would recommend it for the understanding of using less essential oils in a blend. It ties in with a greater understanding of energy fields and sensitivity (with all due respect to the knowledge I have gained from reading Robert Tisserand).

  9. drew February 12, 2015 at 8:37 pm

    Hi Robert thank you for this blog post, I was reading about essential oil safety on another site (http://oilsforskin.com/are-essential-oils-edible/)

    But I didn’t realize how important dilution was until reading this post. I’m planning on buying your book via amazon.

  10. Mark March 23, 2015 at 10:57 am

    I have read this and many articles on dilution of essential oils and all are approximately the same in that they give the calculations for a particular % dilution. However, I have been addressing a more relevant question as to the range of dilution for specific oils. I ask this because each oil possesses unique properties, potency, and tendency toward irritation or sensitization. Therefore it follows that each oil would require a different dilution in order to optimize its safety and efficacy. Is there any publication or web site that addresses this issue?

  11. robert March 26, 2015 at 5:05 pm

    Hi Mark – yes indeed, different oils very often do require different dilutions, either for safety or for efficacy reasons. For example, tea tree oil does not work well for wound healing unless it is used at 5% or more. On the other hand for cosmetic uses, 5% would be a maximum not a minimum. Safety restrictions may be to guard against adverse skin reactions, or to avoid systemic toxicities. You will find a lot of detail on the chemistry and safety in my book http://roberttisserand.com/essential-oil-safety-book-second-edition/

  12. Cindy February 27, 2016 at 3:33 pm

    Hi just found out through a saliva test that I have adrenal fatigue and very high cortisol levels. I heard that lavender essential oil could help. How do I dilute this, with what and how much. Thank you for any help. Cindy

  13. Robert Tisserand February 27, 2016 at 8:58 pm

    Hi Cindy, lavender oil inhalation using a personal inhaler or through room diffusion, or application to the body diluted to about 3% in any vegetable oil or lotion base, can reduce cortisol levels.

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