Essential Oil: Potential Reactions & Warnings

Kristyn Bango

When using essential oils, it's possible to experience adverse or unwanted events. It's important to know what these are and what to look for when using essential oils, so you're able to recognize them and rectify the problem. When using essential oils, it's imperative that you know not only their applications but any potential issues that may arise with their usage. The following are some common adverse reactions that may occur with essential oil use.

Irritant - this can be a skin irritant or mucous membrane irritant that happens when oils are not adequately diluted on the skin or ingested without proper knowledge or guidance from a medical professional. It can present itself in the form of blotchy skin and itching, burning or pain where oil has come in contact with the body.

Essential oils that may be irritating to the skin include those that are high in aldehydes and phenols but are not limited to these. Dermal irritation may occur in some individuals while in others may cause no reaction at all. The degree of irritation may be relevant to the strength of the mixture applied to the skin. These types of reactions are usually localized and short-lived. 

Phenols and aldehydes are often responsible for irritating mucous membranes also.

Common essential oils high in phenols include:


Cinnamon Leaf

Clove Bud and Leaf



Common essential oils high in aldehydes include:



Lemon Eucalyptus



Sensitization - this refers to the possibility of becoming sensitive to a particular oil over time, whether from overuse or improper dilution. Once a person becomes sensitized to an oil, they may no longer be able to use it without encountering some reaction ranging from skin irritation to an allergic reaction. This may also apply to oils with similar chemical components. Contact sensitization can produce a reaction on the skin after numerous uses. These types of reactions may produce no response after the first application but may develop later.

Phototoxicity - these oils may cause sensitivity to the skin when exposed to the sun. Sun burns may occur many hours after application. This is associated with many citrus oils. Sweet orange and mandarin are not phototoxic oils, but bitter orange and wild orange are. Always check if phototoxicity is a concern.


Pregnancy is a time where extra caution should be taken when using essential oils. Some oils may be capable of crossing the placenta and should be avoided in the 1st trimester as their effects on newly formed fetuses have not been studied.  Essential oils may also produce emmenagogue effects which help promote menstrual flow, and these oils should be avoided during pregnancy.


Additional symptoms that may be observed include:





difficulty concentrating


These may be present after inhalation where the scent is readily absorbed.  Effects may be seen in asthmatic people after inhalation where certain fragrances may irritate the respiratory system, which may increase asthmatic and allergic symptoms. These symptoms may increase with prolonged exposure to the irritants. 

 Having a thorough understanding of essential oils allows proper uses and applications to be applied. This knowledge helps avoid serious adverse events. Possible sensitization and allergic reactions can also be easily recognized so usage may be changed or discontinued when necessary.

Want to learn more about essential oils? Pick up my e-book Essential Oil Love on Amazon today!

We also offer Aromatherapy Consultations book your appointment now, for help with specific questions and concerns regarding essential oils, and herbs.

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