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), 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) 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 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 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.

Side effects in detail

Our article cinnamon essential oil: dangers and strong precautions already set the general framework of caution. This companion piece details the side effects actually documented in dermatology, drawing on the available clinical cases, for cinnamon essential oil.

What the reference study on contact dermatitis shows

A study by Ackermann, Aalto-Korte, Jolanki and Alanko, published in 2009 in Contact Dermatitis, documented cases of occupational allergic contact dermatitis, including via airborne exposure, in people regularly exposed to cinnamon at work (bakeries, pastry-making, perfumery). The compound most often responsible is cinnamaldehyde, the main aromatic constituent of cinnamon bark, known for its strong sensitizing potential even at trace levels inhaled or through indirect contact. This finding is a reminder that prolonged diffusion in a closed room can be enough to sensitize a person, without any direct skin contact with the oil.

Catalogue of possible side effects

Effect	Context	Frequency
Contact dermatitis (redness, burning)	Skin application, even diluted, in a sensitive person	Common for an undiluted essential oil
Allergic sensitization	Repeated exposure, including airborne diffusion	Documented in occupational settings
Irritation of the mucous membranes (nose, throat)	Overly concentrated or overly prolonged diffusion	Occasional
Chemical burn	Undiluted application	Rare but severe

Cassia or Ceylon: a difference that matters for the skin

Cassia cinnamon (Cinnamomum cassia), the most common and cheapest kind, is noticeably richer in irritating compounds and coumarin than Ceylon cinnamon (Cinnamomum verum). This difference carries over into the essential oil: the Cassia version is generally considered more dermocaustic, which calls for even stricter dilution and extra vigilance when the botanical origin on the label is unclear.

Reducing the risk in practice

• Never apply undiluted to the skin, whatever the area;
• Dilute heavily (1% maximum, roughly one drop per tablespoon of carrier oil) before any occasional skin use;
• Inner-elbow patch test, 24 hours before first use, even diluted;
• Keep diffusion sessions short, in a ventilated room, to avoid prolonged airborne exposure;
• Stop immediately in case of redness, burning or breathing discomfort.

These pointers complement our article cinnamon essential oil: dangers and strong precautions. General precautions are gathered in our safety and precautions guide.

Pregnancy and breastfeeding: the full picture

Cinnamon essential oil is best avoided during pregnancy without explicit medical advice, including as a diluted skin application. This caution contrasts with cinnamon used in cooking, which our article cinnamon and pregnancy notes is generally considered reasonable at usual culinary intake — the difference lies in concentration. An essential oil packs the active compounds of far larger quantities than a cooked dish into a few drops.

This article completes our reference article cinnamon essential oil with the still-missing pregnancy angle, closing the five-part series already published for this oil (review, dangers, how long, side effects, dosage).

Why This Essential Oil Raises Particular Concern in Pregnancy

Our article cinnamon oil: dangers and precautions already details, based on the study by Ackermann, Aalto-Korte, Jolanki and Alanko published in 2009 in Contact Dermatitis, this essential oil's irritant and sensitizing potential, capable of causing contact dermatitis even through airborne exposure (diffusion). This study does not concern pregnancy, but it establishes a level of skin and respiratory reactivity high enough to justify, as a precaution, avoiding any concentrated exposure during this period, when skin and mucous membranes can be more sensitive.

Added to this is cinnamon's natural coumarin content, particularly in the Cassia variety, already flagged in cinnamon and pregnancy for repeated culinary use: an essential oil concentrates these compounds to a level far above that of a spice, and no study has established a safety threshold for skin or diffused use during pregnancy.

Culinary Spice and Essential Oil: Two Different Logics

Form	Assessment During Pregnancy
Cinnamon powder or stick, in a dish or drink	Generally considered reasonable at usual culinary doses
Essential oil in a diffuser	To be avoided as a precaution, given the already-documented respiratory irritant potential
Essential oil applied to the skin, even diluted	To be avoided without medical advice, for lack of pregnancy safety data
Essential oil taken internally	To be ruled out, as with almost all concentrated essential oils

Why Not Simply Dilute It Further?

Our dosage section already details the very low dilutions recommended for everyday use of this oil, precisely because it is among the most irritating in the herbal pharmacopoeia. During pregnancy, this dilution logic alone is not enough to guarantee a safety that has not been demonstrated: no study has established a dilution threshold considered safe for this specific period, which justifies complete avoidance rather than a simple dose adjustment.

What to Do in Practice

• Cooking: continue using cinnamon powder or stick at usual culinary doses, with no particular change;
• Diffusion and massage: avoid cinnamon essential oil throughout pregnancy, even diluted;
• Alternative for comforting diffusion: favor an essential oil whose compatibility with pregnancy is better established, after advice from a professional trained in aromatherapy;
• After pregnancy and breastfeeding: cinnamon essential oil can be reintroduced following the dilutions detailed in our dedicated article.

What About Breastfeeding?

The same caution applies during breastfeeding, for lack of data on the passage into breast milk of this essential oil's highly concentrated compounds. Culinary use of cinnamon powder remains compatible with breastfeeding under the same guidelines as pregnancy.

Precautions

In summary, cooking with cinnamon during pregnancy carries no identified risk. It is the concentrated essential oil, whether diffused or applied to the skin, that should be avoided without medical advice during this period, given its already-documented irritant potential and the absence of specific safety data. To learn more, see our article cinnamon oil: dangers and precautions, our Ayurveda and pregnancy guide and the safety and precautions guide.

Dosage: usual amounts and duration

Our reference article cinnamon essential oil covers its traditional uses in diffusion and, more rarely, on the skin. This article details the exact quantities to respect: this is one of the essential oils for which a too-generous dilution quickly leads to irritation, as detailed in our article cinnamon oil dangers.

How many drops for diffusion?

Diffuser type	Indicative quantity	Session length
Nebulizing diffuser, 200 sq ft room	2 to 3 drops maximum	15 to 20 minutes
Gentle-heat diffuser	1 to 2 drops	20 to 30 minutes

Unlike gentler essential oils, cinnamon does not lend itself to generous diffusion: beyond these guidelines, the risk of respiratory-tract irritation rises without any added benefit to the diffused scent.

What dilution for occasional skin use?

Professional aromatherapy recommends a maximum dilution around 1% in a carrier oil for this essential oil, roughly one drop of cinnamon essential oil per 5 ml (one teaspoon) of carrier oil. That is notably lower than for most essential oils, whose usual dilution sits more around 2 to 5%.

Amount of carrier oil	Drops of cinnamon essential oil (1% dilution)
5 ml (1 teaspoon)	1 drop
10 ml (2 teaspoons)	2 drops
30 ml	6 drops

Why such a strict dilution?

A study published in 2009 in Contact Dermatitis by Ackermann, Aalto-Korte, Jolanki and Alanko documented several cases of occupational allergic contact dermatitis linked to cinnamon, including one case triggered by mere airborne exposure without direct skin contact. This particular sensitivity justifies scrupulously respecting a low dilution, even for an occasional, localized skin use, and avoiding any repeated application on the same area.

Never orally without professional guidance

Unlike the cinnamon powder used in cooking, the essential oil should never be ingested without the advice of a professional trained in aromatherapy. Its concentration is not comparable to that of the culinary spice: one drop of essential oil is equivalent to several grams of powder.

Precautions

These dilution guidelines do not replace a preliminary 24-to-48-hour skin test before any use, even diluted. Precautions are detailed in our article cinnamon oil dangers. General precautions are gathered in our safety and precautions guide.