What is Sensitization? - Everyday Essentials

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What is Sensitization?

We throw around this big word a lot: Sensitization. We get asked a lot what this means, so here’s a quick lesson that sheds some light on sensitization.

What Does This Mean?

Sensitization is an allergic immune response. It can also be referred to as Allergic Contact Dermatitis (ACD). This means that the reaction may or may not show up at the area of application. If you apply an oil or blend to your arm, the reaction may show up on your chest, neck or just about anyplace else. Sometimes it will take time to figure out which oil you are reacting to. Almost every time the reaction will happen faster and last longer than the time before.

Just like when you get bit by a mosquito or stumble upon poison ivy, a raised, itchy, red rash can appear. It’s that histamine reaction that can worsen over time. It may not happen the first, second, or even tenth time, but the fact remains it may happen. Now, here’s the really sad part: once sensitized to an oil you may not be able to use it without symptoms recurring. You may also have reactions to oils with a similar chemical make-up. An example of this is a compound called geranyl, widely used in modern cosmetics,  there are many people who have sensitization to Lavender since it contains geranyl.

Some signs of sensitization are:

  • itchy skin
  • raised, bumpy rash
  • eczema
  • shortness of breath
  • tightness in chest

How Can I Reduce My Risk?

This is why it is so important to follow proper safety dilutions. If you dilute your oils, you decrease your risk for sensitization. Why risk not being able to use your favorite oil? It is possible that if you use your oils undiluted for a long enough period of time, this can happen. Of course, this is not true in every case but why risk it? Always use the least effective amount of oil needed. I prefer to keep my dilutions to 1-2% for daily or frequent  use. For acute situations, like an injury, I go as high as 4-5 %.  Please refer to the dilution chart for guidelines on proper usage.

Applying products to arm

Higher Risk Essential Oils

If you are prone to allergies, eczema, dermatitis or have sensitive skin you may have an increased risk of sensitization. In this case, always use a lower dilution. Oils to avoid because they are known sensitizers are, Aniseed pimpinella anisum , Cassia cinnamomum cassia, Lemon Verbena Lippia citriodora or Aloysia triphylla, Peru Balsam myroxylon pereirae and Spearmint mentha spicata. There may be other oils that are prone to sensitization. Always do your own research to ensure that the oils you are choosing are right for you!

Using Essential Oils Neat

Does this mean you can’t use essential oils neat? No, not necessarily. There are cases where you can use oils neat, like when touching a hot pan and burn my finger. However, erring on the side of caution here is useful so that when you have a need to use an oil neat you can do so without fear of creating more of a problem for yourself. It is always wise to work with a certified aromatherapist who can guide your safe usage of essential oils. We want to empower your use of essential oils, not create an atmosphere of fear. Please note that we always urge safe, conservative use of essential oils so that you can continue to reap the benefits of these wonderful tools!

Here at Plant Therapy, we have on-staff aromatherapists who are happy to help you answer questions! Contact us at [email protected].


  1. Tisserand, R. (2014) Essential Oil Safety
  2. Fulcher, L. (2012) “Would you know if you had an essential oil “sensitization” reaction?”
  3. Clark, M. (2013) Essential Oils and Aromatics: A step by step guide for use in massage and aromatherapy

54 thoughts on “What is Sensitization?”

  • Once you’re sensitized to an EO, would it be advisable to not ingest that oil either? I was using lemon EO neat a few years ago (though I knew better and always advised others not to!), and then one day had a chemical-burn-like reaction in the middle of the night to the lemon which I’d only applied a few drops of that night to my shirt sleeve. My skin underneath was red and painful (smelled like lemon…and I couldn’t wash the smell away!) and my face where my sleeve had touched had the same reaction. Very painful, and I was worried about scarring. The burns were all up my arm. Amazingly, almost all traces of the burn were gone buy the next day. I’ve just made some whipped cream with a couple drops of lemon oil in it, which I normally wouldn’t have been afraid to try except for knowing I was sensitized a few years ago. I’ve not since used lemon oil on my skin, and just want to be clear on whether I should definitely avoid internal use (properly emulsified, of course) of lemon oil as well. I tasted a little of what I’d made to make sure I had enough stevia powder to sweeten it and to make sure you could taste the lemon yesterday, and then remembered that was probably not a wise decision, and my throat burned a little for maybe 15 minutes after, though I’m not sure if I was just imagining it out of anxiety! Thoughts? Thanks in advance!

    1. Hi Jenna, we don’t recommend the ingestion of essential oils and you can read more about why that is in this great blog post. You can also reach out to our team of aromatherapists at [email protected] with more questions.

    2. If I use a diluted oil ain’t twice a week every week, am I risking sensitization? I use Cypress oil on my legs about twice a week to help with a foot that swells after travel and in the summer . I also use the same 3 oils in a hair mask about twice a week.

  • Thanks for this information. I know people who have heard about the essential oils craze but have not educated themselves. I may have been one of them if it weren’t for Plant Therapy! They use it neat straight out of the bottle for perfume. And, sometimes it is the cheap, store-bought stuff. They don’t know what they don’t know.

  • Thank you for this info. It is very important.
    Is there any sensitization response when diffusing ?

  • This was a really good blog post, important to read as a newbie! Thanks for having so much good information easily available!

  • It says ” If you dilute your oils, you decrease your risk for sensitization.” So even with a dilution the risk is minimized not eliminated? You can get sensitized even if you dilute your oils?

    1. Nora, this is a wonderful question! Diluting essential oils for topical use is one way to minimize that sensitization, however, it can still occur through overuse. That’s why it’s a good idea to switch your oils up occasionally. There really is no sure fire way to prevent sensitization from occurring. It can happen to anyone. There are thing you can do to lessen the likelihood(diluting, intermittent diffusion, etc.) but not a definite way to eliminate sensitization.

  • Hi there! Sensitization! It seems I have been reading this word a lot these days. Before I started using EOs I was diagnosed with contact dermatitis and even had a skin patch. The doc gave me a list of substance/ chemicals I’m sensitive or allergic to which most of personal care products are full of these substances. So I decided I just have to make my own DIYs. But 3 months ago, I developed itchiness on my eyelids and under my eyes skin. Right now I’m so disappointed because I thought I found an answer to my problem. Before it was only in my hands being a health care worker I developed sensitivity with gloves and frequent hand washing and using hand sanitizer. I’m still under the care of a dermatologist but I’m afraid that the meds they’re giving me will have worst side effect in the long run. I don’t know where to go from here and I still use my EOs mainly for diffusing and cleaning but not topically anymore. Any suggestions how to desensitized?

    1. Rose, I’m so sorry to hear that you’re dealing with this uncomfortable experience. If you could please email us at [email protected] so we can gather more information we would love to assist you further. We’re looking forward to hearing from you!

  • Your aromatherapist recommended I read this post as I was not aware that I may have been using my blend improperly by using it all over my face instead of as a spot treatment. She recommended using a weaker dilution rate to avoid this. Maybe this should repost on the blog. LOVE this ompany and thankful for all of the advise, great products and affordability.

  • My 5 year old seems to rub her eyes when I put juniper berry and cedarwood on her for sleep. It’s 2 drops of each in 5 ml fractionated coconut oil. Does this sound like allergy or sensitisation? It hardly affects her if it’s just on her feet. TIA

  • Quick question I think I have become sensitized to Frankincense oil. I was applying it without realizing I wasn’t putting the right ratio of carrier oil to essential oil on my face. If I have become sensitized to the oil, will I ever be able to use it again? Thanks in advance!

    1. Unfortunately, this may be a life long problem now. At the very least, you need to take a significant break from using (any) essential oils. I would recommend several weeks.

  • I think this maybe the cause of the itchy bumpy rash all other my 4 year olds belly and back. How do you figure out which oil is the cause? Stop using all of them and then start testing one by one? How long does it take before rash will go away once you stop using oils?

    1. Yes – it may take a one-at-a-time approach!! If it is sensitization (and not just a rash) this probably means you won’t be able to use the offending essential oil with your child.

  • I was wondering…I did follow a company that promoted using oils neat. I didn’t pay much attention for I was new to it and went ahead with peppermint oil neat on the back of my neck. I broke out in a bad itchy rash in that area. BUT…if I dilute the peppermint oil or diffuse it…i don’t have the problem…unless I dilute improperly. Is this a sensitation issue and I should not use peppermint…or is this just a skin irritation issue from the improper use? It is so hard to tell…I have had that happen to a few oils (vetitver and theives).

  • Does sensitization only happen with topical application or can it happen with inhalation as well?
    I’ve seen comments posted that people will use an EO or blend for a few weeks and then change it for a few weeks to avoid sensitization, what is the maximum time to use an oil before taking a break. How long should you break before going back?

      1. Thank you for the clarification.
        What is the maximum time to use an oil before taking a break. How long should you break before going back?

      2. So to clarify using a cleaning blend weekly or daily would be ok right? What about dryer balls..if I put a few drops of oil on wool dryer balls doesn’t it end up on your skin a little or not enough to cause a sensitization?

        1. It’s so far evaporated that I haven’t had any issues with sensitization, I just get a slight aroma. If you have very sensitive skin it may be better to take a break after a couple of weeks.

  • Glad I saw this. We have been making our own hand soap this way for years, but I was only using about 10 drops of eo in it. I am guessing the higher amount will really help when germs are going around. I have found this to be drying for our hands, but to work around that I add in a few drops of glycerin, and that seems to help a lot. Thanks for sharing, love all the new scent ideas.

  • Thank you for this post! Is a phototoxic reaction the same thing as an allergic immune response? A friend used a 4% dilution of bergamot oil and went out in the sun the next day. She had red rash/sun burn on her arms for a week! Should she avoid this oil in the future?

  • I usually drop some FCO in my palm and mix with a drop of whatever oil I’m using, but this infers a need to dilute much more. The practicality of this for me is what stops me…do you have additional bottles for every oil you use with the carrier oil added? I’m not sure how to make this work for me.

    1. Connie, what a great question! I do keep smaller bottles on hand for creating diluted blends I know I will use often. 10 mL roller bottles are also useful for application – and you can keep them handy in your purse, etc. I hope that helps solve your dilemma

  • I’m posting this link on Facebook with the message “Wow! An essential oil company that actually EDUCATES their customers on the potential for OVERUSING an essential oil, ALLERGIC reactions, and basically saying that LESS is more. I’m falling more in love with Plant Therapy.”

    Seriously. I’ve been highly impressed with the safety concerns Plant Therapy shows.

    1. Thank you for those kind words. We strive, with all we do, to ensure that our customers feel empowered to use essential oils in a safe, responsible manner. We want you to be your own best health advocate. At Plant Therapy, if you ask a question and we don’t feel essential oils are the answer – we’ll try to point you to a source that may help or advise that you speak to your physician. Essential oils are amazing – but we know they aren’t right for every situation or for everyone! Thanks for being a loyal customer! Referrals to our business are the best form of flattery!

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