Cinnamon cassia oil is an essential oil extracted from the bark of the Cinnamomum cassia tree, a species native to China and widely cultivated across Southeast Asia. Its dominant compound, trans-cinnamaldehyde, typically makes up 82% to 92% of the oil, giving it the warm, spicy, slightly sweet aroma most people associate with cinnamon. This is the variety behind most commercial cinnamon products and is distinct from Ceylon cinnamon, which comes from a different species.
Where It Comes From
Cinnamomum cassia, sometimes called Chinese cinnamon, grows primarily in southern China but is also cultivated in Vietnam, Indonesia, and other parts of tropical Asia. The oil is produced through steam distillation of the inner bark. Branch bark tends to yield more oil (2.7% to 3.1% by weight) than stem bark (0.4% to 2.6%), depending on the tree’s age and which section of the trunk is harvested. China’s official pharmacopoeia sets a minimum oil content of 1.2% in dried bark for quality purposes.
The bark can be harvested at different stages of growth, and the age and location on the tree affect both the amount of oil produced and its chemical profile. Leaves also contain cinnamaldehyde, though bark oil is the standard commercial product.
What’s in the Oil
Trans-cinnamaldehyde dominates the composition, with most analyses placing it between 82% and 92% of the total oil. The remaining fraction includes smaller amounts of cinnamyl acetate (around 3% to 5%), benzaldehyde, coumarin (roughly 1.2%), and trace compounds like phenylethanol and methoxy-cinnamaldehyde. The high cinnamaldehyde concentration is what gives cassia oil its intense flavor and most of its biological activity.
This composition differs noticeably from Ceylon cinnamon oil, which contains more eugenol and far less coumarin. Cassia oil’s coumarin content is one of the main reasons the two types of cinnamon are treated differently in food safety guidelines.
Antimicrobial and Antifungal Properties
Cassia oil has well-documented activity against bacteria and fungi. Cinnamaldehyde is hydrophobic, meaning it can penetrate the fatty outer membranes of microbial cells, disrupt their structure, and increase permeability until the cell dies. Its aldehyde groups can also cross-link with fungal DNA and proteins, interfering with reproduction. Studies have confirmed the oil’s effectiveness against common fungal contaminants like Saccharomyces cerevisiae and Acremonium species, both of which cause spoilage in fruit products.
These properties make cassia oil useful in food preservation and surface cleaning applications. It’s one of several essential oils being explored as a natural alternative to synthetic preservatives.
Effects on Blood Sugar
One of the most studied aspects of cassia cinnamon is its potential influence on blood sugar levels. The exact compound responsible is still debated. Early research pointed to a polymer called MHCP, which appears to mimic insulin by binding to cell receptors and promoting glucose uptake. More recent work suggests that polyphenols in cinnamon, particularly one called polyphenol A, may also play a role.
The effects seem to go beyond simply helping cells absorb glucose. Research from Nutrition and Metabolic Insights found that cassia cinnamon’s impact on blood glucose values was greater than dietary changes alone, suggesting that one or more compounds alter broader carbohydrate metabolism rather than acting through a single pathway. These findings are promising but the mechanisms are not yet fully mapped.
Traditional Medicine Uses
Cassia cinnamon has been used in Traditional Chinese Medicine for nearly 2,000 years. Its earliest recorded use appears in the Shennong Bencao Jing, a foundational medical text from the Eastern Han Dynasty (25 to 220 AD), where it was prescribed for arthritis. Other classic texts documented its use as a painkiller and a treatment for abdominal pain and menstrual cramping.
Today, more than 500 formulas in the Pharmacopoeia of the People’s Republic of China contain cassia bark. Modern TCM applications include cardiovascular disease, chronic gastrointestinal conditions, gynecological disorders, inflammatory disease, kidney problems, and diabetes management. The range is broad, reflecting centuries of empirical use across multiple medical traditions in China, India, Indonesia, and beyond.
Cassia vs. Ceylon: The Coumarin Question
The most important safety distinction between cassia and Ceylon cinnamon is coumarin content. Cassia contains roughly 1% coumarin, while Ceylon cinnamon contains about 0.004%. In measured samples, cassia bark has been found to contain up to 116 mg of coumarin per kilogram, compared to as little as 5.6 mg per kilogram in Ceylon cinnamon. Coumarin can cause liver damage at high doses, which is why the European Food Safety Authority set a tolerable daily intake of 0.1 mg per kilogram of body weight.
For a 70 kg (154 lb) person, that limit is 7 mg per day. If you’re using cassia cinnamon occasionally in cooking, this is rarely a concern. But people who consume large daily doses of cassia cinnamon for blood sugar management or other health reasons could exceed that threshold. Switching to Ceylon cinnamon or monitoring intake is a practical option for regular users.
Safe Use on Skin
Cassia oil is one of the more irritating essential oils when applied topically. Cinnamaldehyde activates pain and heat receptors in the skin, which is why undiluted cassia oil can cause burning, redness, or allergic sensitization. General dilution guidelines from the Tisserand Institute suggest ranges based on application type: 0.2% to 1% for sensitive or compromised skin, 0.5% to 1.2% for facial products, and 1% to 3% for body oils and lotions. Cassia oil falls into a category of oils that carry specific restrictions beyond these general ranges, so lower dilutions are typically recommended.
If you’re using cassia oil in a diffuser, standard intermittent use (30 minutes on, 30 minutes off) is the common approach. Direct skin application without a carrier oil like coconut, jojoba, or sweet almond is not recommended.
Food and Regulatory Status
The U.S. Food and Drug Administration lists cinnamon bark oil (Cinnamomum spp.) as Generally Recognized as Safe for use as a flavoring agent. It carries FEMA number 2291 and is regulated under 21 CFR 182.206. This means it’s approved for use in food products at concentrations typical for flavoring, not for therapeutic dosing. The distinction matters: a few drops in a recipe is a different exposure than taking capsules of concentrated oil daily.