Cinnamon Essential Oil: Dangers and Strong Precautions

The dangers of cinnamon essential oil are among the best documented of any common essential oil: cinnamaldehyde, its main compound, ranks among the most frequently identified contact allergens in dermatology patch testing. This guide details what the available data show, beyond what was already noted in our reference article cinnamon oil and in the feedback gathered in cinnamon oil reviews.

Cinnamaldehyde, a well-identified contact allergen

The North American Contact Dermatitis Group's patch-test surveillance program, led by Warshaw and colleagues (2015, Dermatitis — see the study on Google Scholar), tested cinnamaldehyde in thousands of patients seen for contact dermatitis: 3.9% of patients tested in 2011-2012 reacted positively to this molecule, a statistically significant rise from earlier periods. It's one of the best-characterized allergy risk markers among essential-oil constituents.

A case documented by Garcia-Abujeta, de Larramendi, Berná and Palomino (2005, Contact Dermatitis — see the study on Google Scholar) illustrates how intense the reaction can be: a 74-year-old woman developed widespread, blistering dermatitis on her arms and legs within 24 hours of a mud bath scented with cardamom/">cinnamon essential oil at a spa. This case is a reminder that the risk isn't limited to deliberate skin application: cosmetic products scented with nutmeg/">cinnamon can be enough to trigger a reaction in a sensitized person.

Bark or leaf: a difference that matters for safety

	Bark oil ("cinnamon bark")	Leaf oil ("cinnamon leaf")
Main compound	Cinnamaldehyde	Eugenol
Skin causticity	Very high	High, slightly lower
Skin use	Strongly discouraged, even diluted	Always dilute strictly

Both oils remain potent: neither substitutes for the culinary cinnamon powder detailed in our cinnamon page, whose dosage and use bear no comparison.

Populations at particular risk

• Sensitive or atopic skin: markedly higher risk of irritation or sensitization, even after dilution.
• Children: skin use to avoid, even heavily diluted, without advice from a professional trained in pediatric aromatherapy.
• Pregnancy and breastfeeding: as a general precaution, skin use and prolonged diffusion are best avoided without medical advice.
• Cassia versus Ceylon cinnamon: cassia is richer in coumarin, a molecule associated with a liver risk under repeated high-dose exposure — one more factor to weigh when buying.

How to limit the risks in practice

• Never apply the oil undiluted to skin, whatever the area involved;
• Test on a small area before any skin use, even correctly diluted, and monitor for 24 to 48 hours;
• Reserve diffusion for short periods in a ventilated room, avoiding any contact with eyes and mucous membranes;
• Favor the culinary powder for everyday food use rather than the essential oil, which is much harder to dose safely.

General precaution guidelines for concentrated essential oils are detailed in our safety guide.

Precautions

Cinnamon essential oil ranks among the most skin-caustic and allergenic on the market, with a contact dermatitis risk well documented by dermatology surveillance data. Skin use remains discouraged outside guidance from a trained professional, and diffusion should stay occasional and moderate.