Essential Oil Risk: What is Skin Sensitization?

Friday, April 27, 2018

Essential Oil Risk: What is Skin Sensitization?

In recent years, more and more people are using essential oils in various applications. In Philippines alone, you will see a lot of people selling essential oils online – it’s like the latest craze in the country. What worries me is that there are a lot of essential oil enthusiasts who are not aware about the possible risks associated with the use of essential oils. In fact, there has been also a rise of reported cases of people who got adverse reactions from the improper use of essential oils.

Even though essential oils are considered natural (since they are plant-derived), a couple of skin reactions may occur if they are use in the wrong way. These skin reactions include irritation, sensitization and photosensitivity (a.k.a. phototoxicity). The focus of this article is skin sensitization.

Skin sensitization (also known as Allergic Contact Dermatitis) is a type of allergic reaction to essential oil when it comes into contact with skin. It could either be immediate or delayed allergic reaction. Immediate allergic reaction occurs upon first dermal contact with the essential oil. It is also possible not to get any allergic reaction on first exposure but during subsequent exposures – this is called delayed allergic reaction. Regardless of the type of sensitization, the symptoms are the same:
  • Rashes/hives
  • Blisters
  • Itchy red skin
  • Chemical burn
The skin reaction may or may not show up on the actual area where you applied the essential oil. For example, it is possible that you applied the essential oil to your arms but the allergic reactions appeared on your chest area. Skin reactions also vary for each person and are dependent on the type and amount of essential oils used.

Once a person became sensitized with one essential oil, he is most likely to be allergic to it for the rest of his life. It means he won’t be able to use that particular essential oil (or oils belonging to the same family) without experiencing sensitization.

How to Avoid Skin Sensitization When Using Essential Oils?

1. Dilute Essential Oils Properly

Most reported cases of skin sensitization are due to using undiluted (neat) essential oils on the skin. It is very important to ALWAYS dilute essential oil in carrier oil (vegetable oil). Contrary to what you read in most DIY articles, the following items CANNOT dilute essential oils: witch hazel, full-fat milk, vinegar and salt. Actually, I used to believe that witch hazel can dilute essential oils until my recent studies where I learn that witch hazel only contains 14% alcohol (ethanol), wherein the required amount is 95% for essential oil dilution.

It is equally important to know the proper dilution amount for essential oil. I always use the smallest dilution in my cosmetic formulations, which is 0.5 – 1% dilution of essential oil (or blend of essential oils). It is best to measure the dilution in weight (rather than in drops) using a digital scale. If you don’t have a digital scale and prefer measuring in drops, then you can use this Tisserand Institute’s dilution chart as a guide. Take note also that each essential oil has its own maximum dermal limit. For instance, lemon essential oil should not be used at more than 2% dilution.

2. Do Not Overuse Essential Oils

There are several people who apply multiple essential oils on their body several times a day, every single day for a long period of time. This could cause skin sensitization due to overuse of essential oils, most specially undiluted or improperly diluted essential oils. I usually just use 1 to 3 essential oils per day and only apply them once or twice at most in a day. Also, when I’m making my own blend of essential oils, I limit my formulation to a maximum of 4 essential oils. In case I’ll have sensitization with the blend, it would be easier for me to find the culprit since I only use less essential oils. “Less is more” is the rule I set for myself when it comes to essential oils.

3. Avoid Essential Oils That Are Known Skin Sensitizers

Some essential oils are known to cause dermal sensitization, which means there is a high probability you’ll get sensitized if you use them, so avoid them at all cost!

The following table lists essential oils that are known skin sensitizers.

Backhousia citriodora
Cinnamomum cassia
Cinnamon Bark
Cinnamomum zeylanicum
Costus Root
Sausurrea costus
Elecampane Oil
Inula helenium
Fig Leaf Absolute
Ficus carica
Oak Moss Absolute and Resinoid
Evernia prunastri
Peru Balsam
Myroxylon pereirae
Rue Oil
Ruta graveolens
Juniperus sabina
Styrax Gum
Liquidambar orientalis
Tea Absolute
Camellia sinensis
Tree Moss Absolute
(Pseudeo) Evernia furfuracea
Turpentine Oil
Pinus spp.
Verbena Absolute
Lippia citriodora
Oxidized oils from Pinaceae family (e.g. Pinus & Cupressus species) and Rutaceae family (e.g. citrus oils)

4. Do Not Apply Essential Oils to Open Wound

Some essential oils have healing properties so it is not unusual to see people who apply essential oils to fresh, open wounds. However, professional aromatherapists don’t recommend this as it could make your skin more vulnerable to skin sensitization. Take for example this case of a woman who developed rashes after applying frankincense essential oil to her open wound. The right way to do this is to wait for the wound to close up a little before applying essential oils that further promote healing.

Essential oils have so many wonderful benefits. However, if not used properly they could possibly do more harm than good so it is very important to stay educated to avoid possible risks associated to the use of essential oils.


Moore, G. (2016, January 5). Sensitization – What is It and How to Reduce the Risk. Retrieved from

Tisserand Institute: Adverse Reaction Database. Retrieved from

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Disclosure: This post contains affiliate links, which means that if you click on one of the product links and purchase the products, I’ll receive some commission.

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