Are there any negative side effects to cinnamon?

October 28, 2025 •

4 min read

With its popularity in both culinary and medicinal applications, many people ask: are there any negative side effects to cinnamon? The answer depends heavily on the type and quantity consumed, as the common Cassia variety contains a compound called coumarin that can be toxic to the liver in large doses.

Quick Summary

Excessive consumption of cinnamon, particularly the Cassia type, can lead to liver damage, low blood sugar, and mouth sores due to its high coumarin content. Potential drug interactions and allergic reactions are also possible, though Ceylon cinnamon is significantly safer for regular use. Moderation and choosing the right variety are key.

Key Points

Two Types, One Major Risk: Cassia cinnamon contains high levels of coumarin, a compound toxic to the liver in large doses, whereas Ceylon cinnamon is low in coumarin and safer.
Liver Damage is a Primary Concern: Excessive consumption of Cassia cinnamon over time can lead to liver toxicity, especially for those with pre-existing liver conditions.
Mind Your Medication: Cinnamon can interact with blood thinners and diabetes medication, potentially causing dangerous drops in blood sugar or increased bleeding risk.
Be Aware of Allergic Reactions: Though rare, allergies to cinnamon or its compounds can cause mouth sores, skin rashes, and in severe cases, anaphylaxis.
Safe Use is Possible: For regular or high consumption, opt for Ceylon cinnamon. For normal culinary use, both are generally safe in moderation.
Avoid the 'Cinnamon Challenge': Inhaling large amounts of cinnamon powder can cause severe respiratory issues, including lung inflammation.

Understanding the Different Types of Cinnamon

Not all cinnamon is created equal. The two main types available commercially are Cassia and Ceylon, and they differ significantly in their chemical makeup and potential side effects. Cassia cinnamon is the variety most commonly found in grocery stores due to its lower cost and stronger flavor. It is also, however, much higher in a naturally occurring compound called coumarin, which is the primary concern for those worried about cinnamon's side effects. Ceylon cinnamon, often called "true" cinnamon, is lighter in color, has a milder flavor, and contains only trace amounts of coumarin, making it the safer choice for regular or heavy consumption.

Liver Damage from Coumarin in Cassia Cinnamon

The most significant risk associated with excessive cinnamon intake is liver damage caused by coumarin, which can be hepatotoxic in high doses. While it's unlikely that normal culinary use would cause problems, consistently consuming large amounts of Cassia cinnamon, especially in supplement form, can be problematic for sensitive individuals or those with pre-existing liver conditions. The European Food Safety Authority (EFSA) sets a tolerable daily intake (TDI) for coumarin at 0.1 mg per kilogram of body weight. A single teaspoon of Cassia cinnamon can sometimes exceed this daily limit, highlighting the need for caution.

Symptoms of Coumarin Toxicity

Symptoms that may indicate coumarin toxicity include:

Tiredness and fatigue
Nausea
Jaundice (yellowing of the skin and eyes)
Abdominal discomfort
Dark urine
Pale stools

Other Potential Negative Side Effects

Beyond liver concerns, other adverse reactions can arise from overconsumption of cinnamon:

Mouth Sores: The compound cinnamaldehyde can cause an allergic reaction called "cinnamon stomatitis," leading to mouth and lip sores or irritation in some people. This is often linked to prolonged contact from sources like chewing gum or toothpaste.
Low Blood Sugar: While cinnamon's ability to help lower blood sugar can be beneficial for some, consuming too much, particularly for those on diabetes medication, can cause blood sugar to drop dangerously low (hypoglycemia).
Breathing Problems: Accidentally inhaling ground cinnamon powder, as seen in the dangerous "Cinnamon Challenge," can cause severe coughing, gagging, and irritation of the throat and lungs. In extreme cases, it can lead to lung inflammation or even aspiration pneumonia, especially for those with asthma.
Allergic Reactions: Though uncommon, some individuals may have a true cinnamon allergy, which can trigger a variety of symptoms, from skin rashes and hives to more severe reactions like anaphylaxis.

Cinnamon Side Effects: Cassia vs. Ceylon Comparison


Feature	Cassia Cinnamon	Ceylon Cinnamon
Coumarin Content	High	Very low, often trace amounts
Primary Health Risk	Liver damage with excessive intake	Generally considered safe for regular consumption
Flavor Profile	Strong, spicy, and slightly bitter	Mild, sweet, and delicate
Appearance	Hard, single-layer sticks; dark reddish-brown	Delicate, multi-layered quills; lighter tan color
Availability	Most common in supermarkets	Pricier; found in specialty stores or online

Drug Interactions

Cinnamon can interact with several types of medications, and it is vital to consult a healthcare provider if you are taking any of the following:

Blood Thinners: The coumarin in Cassia cinnamon has blood-thinning properties, which can increase the risk of bleeding in individuals taking anticoagulant medications like warfarin.
Diabetes Medications: The blood sugar-lowering effect of cinnamon can be compounded by diabetes drugs, potentially leading to dangerously low blood sugar levels.
Hepatotoxic Drugs: If you are taking medications that can affect the liver, such as statins or acetaminophen, excessive coumarin intake from Cassia cinnamon could further increase the risk of liver damage.

How to Use Cinnamon Safely

For most people, using cinnamon in small amounts as a culinary spice is perfectly safe. The key is moderation and being mindful of the type you are consuming. If you use cinnamon frequently or in larger quantities, such as in supplements, choosing Ceylon cinnamon is the safest option. Always check the product label, and if it just says "cinnamon" without specifying, it is likely the higher-coumarin Cassia variety. For therapeutic uses or if you have any pre-existing health conditions, consult a healthcare professional.

Conclusion

While cinnamon offers a variety of potential health benefits, it is not without its risks, especially when consumed excessively. The primary concern is the high coumarin content found in Cassia cinnamon, which can pose a threat to liver health. Being aware of the distinction between Cassia and Ceylon varieties is crucial for mitigating these risks. By exercising moderation and making informed choices, you can enjoy the flavor of cinnamon while avoiding its potential negative side effects. For those with medical conditions or taking certain medications, professional advice is essential to ensure safety.

For more detailed information on coumarin and its effects, you can visit the European Food Safety Authority's website.

Frequently Asked Questions

Excessive and prolonged consumption of Cassia cinnamon can be bad for your liver due to its high coumarin content. The risk is highest for those who consume large amounts or have a pre-existing liver condition.

Ceylon cinnamon is significantly safer for regular, daily consumption because it contains only trace amounts of the liver-toxic compound coumarin. Cassia cinnamon is high in coumarin and should be consumed in moderation.

Yes, cinnamon can lower blood sugar levels. This can be a risk for people taking diabetes medication, as combining the two could cause blood sugar to drop too low.

Symptoms of a cinnamon allergy can range from mouth sores and skin rashes to more serious reactions like difficulty breathing, swelling, hives, and in rare cases, anaphylaxis.

For Cassia cinnamon, it is recommended to limit intake to about half a teaspoon or less per day, especially for regular consumption. There is no official limit for Ceylon cinnamon, but moderation is always advised.

Yes, cinnamon can interact with medications for diabetes, blood thinners, and drugs that can affect the liver, such as statins. Always consult a doctor if you are on medication before taking cinnamon supplements.

Cinnamon is generally safe for children in small, culinary amounts. However, avoid cinnamon supplements, which contain concentrated amounts, and ensure you use the low-coumarin Ceylon variety if using it regularly.