Essential Oil Sensitization: Are you at risk?

Essential oils are beautiful gifts from nature and they are use has become increasingly popular. However, they are highly concentrated product of plant material and when used incorrectly and not in accordance to safety principles can be irritating at least and toxic and even in some cases lethal at most.

One of the first safety issues an aromatherapist learns in their training is to understand the three important reactions to the skin when essential oils are used topically. These are:

  1. Irritation (localized to the areas where the product has been applied)
  2. Phototoxicity (a light-induced reaction to a photoactive essential oil that requires contact with the aromatic then subsequent exposure to UV light)
  3. Sensitization (an allergic reaction that shows up in places other than where the oil was applied).

Essential oil allergic reaction, known as sensitization, is the worst.

Sensitization is in its essence an allergic immune response and can also be referred to as Allergic Contact Dermatitis (ACD). The skin normally reacts in the form of a rash, blotchy redness, often accompanied by slight blistering. One important clue about sensitization is that the reaction may or may not show up at the area of application. For example, if you apply an oil or blend to your arm, the reaction may show up on your chest, neck or just about anyplace else.

woman with symptoms of allergic contact dermatitis


Sometimes it will take time to figure out which oil you are reacting to. Sensitization is considered to be unpredictable as some individuals will be sensitive to a potential allergen and some will not.

However, once sensitization occurs with a specific essential oil, with subsequent use almost every time the reaction will happen faster and last longer than the time before.  Thus, if an essential oil causes a reaction, it should be discontinued immediately as it is highly possible that next time the reaction will be more severe.

What can you do?


First and foremost, do not apply undiluted essential oils straight from the bottle on your skin. Always mix first with a carrier oil in a low dilution between 1% and 3%. You may have seen people on social media applying oils straight from the bottle – even adding to water or cooking with them - typically sold by multi-level marketing companies. This is NOT a safe practice and no qualified aromatherapist will ever recommend this.


Please do a patch test first, especially with new and unfamiliar oils. Add a tiny bit of the diluted substance to the inner elbow and cover it.  Wait an hour or two.  If there is itchiness, even slight, avoid the oil!


At the very least read the safety precautions from the essential oil supplier and read about the oil from reputable sources. There is so much misinformation on the internet so working with reputable suppliers and finding trustworthy information is key!


Even lavender can cause sensitization when used in prolonged period of time. It is a good idea to take a break from a specific essential oil after a certain period of use and even a good idea to occasionally take a little break from essential oils to allow your senses to take a break.

Which oils are sensitizers?

As mentioned, sensitization is highly individual so you should pay attention with every oil but there are certain oils that are considered dermal sensitizers.

High risk sensitizers: Luckily, these are more exotic oils that most people will not be using on a day to day basis, including cinnamon bark, fig leaf absolute, oakmoss absolute, saffron oils

Medium risk sensitizers: Peru balsam, clove bud, clove leaf, cinnamon leaf, lemon verbena, jasmine, styrax, lemongrass, may chang, Melissa.

Low risk sensitizers: Benzoin, citronella, lemon thyme, palmarosa, lemon basil, spearmint, geranium, tea tree.

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