Cassia Oil

• Skin: cassia oil is on the high-risk list for rashes and lasting allergy. Never put it on skin undiluted.. The Tisserand Institute (aromatherapy safety educators) says cinnamon bark and cassia oils are regarded by dermatologists and aromatherapists as high risk for adverse skin reactions, and that its 2015 survey of 345 users confirmed they are high-risk oils on the skin. We read only the free summary, not the paid report, so no reaction rate is given here. NAHA lists cassia as a dermal sensitiser that is not recommended in aromatherapy massage. NCCIH says some cinnamon oil or powder on the skin may cause irritation or contact dermatitis. Cinnamal (the allergen name for cinnamaldehyde), cinnamyl alcohol, coumarin and eugenol are on the European list of fragrance chemicals most often reported as consumer contact allergens. Case reports show how bad it can get: one woman had long-lasting, blistering dermatitis within 24 hours of a spa mud bath with cinnamon oil and was still allergic to cinnamal and related fragrances 5 years later; six patients had delayed allergy to cinnamon, one from airborne exposure. Poison Control says pure oils are potent, that a rash should be washed off at once, and that oils should not go on damaged skin. A sensitisation allergy can last for years and can spread to other fragrances. Authoritative guidance ^{23 14 15 6 8 2 19}
• Do not swallow cassia oil, and do not put it in the mouth, in baths or near the eyes.. Poison Control says misuse of essential oils can cause serious poisoning, that some are poisonous if swallowed or absorbed, and that swallowed oil can enter the lungs and cause pneumonia. NAHA says cinnamon bark oil irritates mucous membranes and should be avoided in baths completely; its tables name cinnamon bark (Ceylon), not cassia, so we cannot say whether cassia is milder. A 1989 case report of toxic effects after a child swallowed cinnamon oil exists, but PubMed holds only its title, so we cannot describe what happened. We found no cassia-specific poisoning series and no toxic amount, and this page gives none. If an oil may have been swallowed, call poison control (US: 1-800-222-1222) or your emergency number. Authoritative guidance ^{19 14 18}
• Coumarin and the liver: a question about cassia bark spice, not shown for the oil.. NCCIH says coumarin in cassia cinnamon has been reported to interact with the liver, that usual food amounts do not generally contain enough to cause significant problems, that some cassia products contain high levels, and that prolonged use could be an issue for sensitive people such as those with liver disease. A review of coumarin says it is toxic to the liver, that a subgroup of people is more susceptible than animals for unknown reasons, and that heavy consumers of cassia cinnamon may reach the tolerable daily intake. Another review gives up to 3.6 g/kg coumarin in cassia against 15 mg/kg or less in Ceylon cinnamon, and a 2025 lab study found up to 43.73 mg/g coumarin in extracts of some cinnamon products. A 2025 case report describes liver injury in a woman after long-term cinnamon for weight loss (species not stated); it cleared after she stopped. For the oil: one 2026 analysis of a cassia bark oil lists coumarin as a minor constituent, with no amount in the abstract. No source we read measured coumarin across oils, so do not assume the spice figures apply to the oil. Authoritative guidance ^{15 1 3 13 24 4}
• Keep it away from children and pets.. Poison Control says children have thin skin and immature livers and may be more susceptible to toxic effects, and that oils at home must be locked out of sight and reach of children and pets (or discarded if young children are in the home). Pet Poison Helpline says essential oil poisoning can affect many species and that cats and birds are at the greatest risk; its page does not name cassia or cinnamon, which is not proof that it is safe. We found no study of cassia oil in children or pets. Authoritative guidance ^{19 17}
• Pregnancy and breastfeeding: not shown to be safe.. A 1999 review says the safety of aromatherapy oils in pregnancy, childbirth and babies has not been clearly demonstrated. NCCIH says larger amounts of Ceylon cinnamon in pregnancy are considered unsafe and little is known about larger amounts of Ceylon or cassia while breastfeeding; those statements are about the spice, not the oil. We found no study of cassia oil in pregnancy or breastfeeding. Not having data is not proof of safety. Ask a midwife or doctor before using any essential oil. Narrative review ^{11 15}
• Quality: a bottle may not be what the label says.. Poison Control says essential oils are not well regulated and it can be hard to know the species, concentration or contaminants. NCCIH says cinnamon products often do not state species or part, and that the types and parts differ in chemistry. Cassia oils vary a lot (four chemotypes across 20 oils; leaf oil changes with season), and in one 2025 lab study ready-made cinnamon products bought from a herbalist showed no detectable cinnamaldehyde or coumarin. Authoritative guidance ^{19 15 9 5 13}

NCCIH says coumarin in cassia cinnamon has been linked to liver problems in reports and that prolonged use could matter for people with liver disease. A 2025 case report describes liver injury after long-term cinnamon for weight loss, which recovered after stopping. These concern the bark spice. One analysis of a cassia bark oil lists coumarin as a minor constituent without an amount, so the oil is not known to be free of it. LiverTox was not opened. ^{15 24 1 4}

How often. Not established.

Monitoring. Not applicable. People with liver disease should ask a clinician about any cinnamon product.

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This is a safety connection. It is not evidence that Cassia Oil supports liver health.

Summary. No lethal or toxic amount for cassia oil is described in the sources we read, and none is stated here. Poison centres warn about essential oils in general.

Amounts. No safe amount is established, and this page gives none.

Onset and course. Not described for cassia oil.

Repeated use. Repeated skin exposure is the route linked to contact allergy in oils generally; occupational allergy to cinnamon is described (six patients).

Animal data. A mouse study reports an oral toxicity test of cassia bark oil; the number is not repeated because it is animal data and could be mistaken for guidance. Pet Poison Helpline names cats and birds as most at risk from oils in general and does not name cassia.

Toxic parts. The oil is a concentrate from bark or leaf. Cinnamaldehyde (about 87% to 92% of the oils measured) is the main compound and the cinnamal allergen. Coumarin was a minor constituent in one bark oil.

Not read. The full EFSA coumarin opinion, IFRA and EU cosmetic limits, Tisserand's paid survey report and safety data, LiverTox, LactMed and veterinary papers were not read.

What is in a bottle can differ from the label, and cassia oil varies a lot.

Unknown species, strength and contaminants. Poison Control says it can be hard to know the species, concentration or contaminants in an essential oil. NCCIH says cinnamon products may not say which species or part was used. ^{19 15}

Composition varies. Twenty cassia oils from different places fell into four chemotypes; leaf oil changed with the season (trans-cinnamaldehyde about 91% to 93% in spring and autumn); bark and leaf oils differ in minor aroma compounds. ^{9 5 10}

Different plants sold as cinnamon. Cassia (C. cassia or C. aromaticum) and Ceylon cinnamon (C. verum or C. zeylanicum) are different trees with different coumarin levels; NCCIH says studies often do not say which was used. Labels such as cinnamon bark oil and cassia oil may or may not be the same species. ^{15 3}

Products without the expected compounds. In a 2025 lab study, ready-made cinnamon products bought from a herbalist showed activity but no detectable cinnamaldehyde or coumarin. That study was of spice products, not oils; it shows how much labels can differ from contents. ¹³

• If a child or pet may have swallowed any essential oil, call poison control (US: 1-800-222-1222) or your local emergency number right away. For a pet, call a vet or an animal poison helpline.
• Swelling of the face or throat, trouble breathing, or a spreading or blistering rash after contact with an oil needs urgent medical care.
• Choking or coughing after oil is swallowed can mean it has entered the lungs: seek emergency care.
• A rash after use: stop, wash the oil off, and see a doctor if it does not clear.
• Yellow skin or eyes, dark urine or belly pain after taking any cinnamon product: see a doctor.

Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.