Are there any negative effects of cinnamon?

November 12, 2025 •

4 min read

Research from the European Food Safety Authority suggests a tolerable daily intake of 0.1 mg of coumarin per kilogram of body weight, a compound found in certain types of cinnamon. This highlights that while cinnamon is generally safe, there are indeed negative effects of cinnamon when consumed in excessive amounts, depending on the variety and individual health factors.

Quick Summary

Excessive intake of cinnamon, especially the common Cassia variety, can cause liver damage due to its coumarin content. Other risks include allergic reactions, mouth sores, and medication interactions.

Key Points

Cassia Cinnamon contains high coumarin levels: This common, inexpensive variety can cause liver damage if consumed in excessive amounts over a long period.
Ceylon Cinnamon is safer for frequent use: The 'true' cinnamon contains only trace amounts of coumarin, making it the better choice for those who use it often or in larger quantities.
Excessive intake can cause mouth sores and allergies: High doses of cinnamon's cinnamaldehyde can lead to allergic reactions, including irritating mouth sores known as stomatitis.
Cinnamon can lower blood sugar too much: While beneficial for blood sugar control, excessive amounts or interactions with diabetes medication can cause dangerous hypoglycemia.
Supplements require caution: Cinnamon supplements are not regulated and may contain high levels of coumarin, so they should be approached with care and medical consultation.
Medication interactions are a risk: Cinnamon can interact with blood thinners, diabetes medication, and liver-affecting drugs, so consult a doctor if you are on medication.

Understanding the Different Types of Cinnamon

Before diving into the potential negative effects, it is crucial to understand that not all cinnamon is created equal. The two most common types are Cassia and Ceylon.

Cassia Cinnamon

Cassia is the most widely available and inexpensive type of cinnamon, typically found in most grocery stores. This variety originates from China and has a stronger, spicier flavor. However, it contains high levels of a compound called coumarin, which can be harmful to the liver when consumed in large quantities. Cassia is the primary concern when discussing the negative effects of cinnamon.

Ceylon Cinnamon

Also known as “true” cinnamon, Ceylon comes from Sri Lanka and has a milder, sweeter flavor profile. Crucially, it contains only trace amounts of coumarin, making it a much safer option for frequent or high-dose consumption. This is why experts recommend Ceylon cinnamon for those who are concerned about coumarin intake.

Potential Health Risks of Excessive Cinnamon Intake

When discussing the question "Are there any negative effects of cinnamon?", the focus is primarily on the excessive, long-term consumption of Cassia cinnamon due to its high coumarin content.

Liver Damage

This is one of the most serious potential side effects associated with high coumarin intake from Cassia cinnamon. In sensitive individuals, or with very high doses, coumarin can cause hepatotoxicity, or liver injury. Symptoms can include abdominal pain, dark urine, and jaundice, though these are typically reversible when intake is reduced. While regular culinary use is unlikely to cause problems, those with pre-existing liver conditions or who take supplements should be cautious.

Mouth and Skin Irritation

Some individuals may experience allergic reactions to cinnamaldehyde, the compound that gives cinnamon its flavor. Ingesting high amounts, such as through cinnamon-flavored products or powders, can lead to mouth sores, swelling, and a burning sensation, a condition known as cinnamon stomatitis. When applied topically, cinnamon oil or powder can also cause skin irritation or contact dermatitis.

Lowered Blood Sugar

Cinnamon is well-regarded for its potential to help lower blood sugar levels and improve insulin sensitivity. However, in excess, this effect can be a double-edged sword. For individuals with diabetes, especially those on blood-sugar-lowering medication, taking too much cinnamon can cause blood sugar to drop too low, leading to hypoglycemia. Symptoms of hypoglycemia include tiredness, dizziness, and potential fainting.

Breathing Problems

Attempting viral internet challenges like the "cinnamon challenge," which involves consuming a tablespoon of dry cinnamon, can be extremely dangerous. The fine texture of the powder makes it easy to inhale, which can irritate and damage the lungs. The spice's fibers can accumulate in the lungs and potentially lead to aspiration pneumonia and permanent scarring.

Medication Interactions

Cinnamon can interact with several types of medication, enhancing their effects or side effects. This is particularly relevant for those taking drugs for diabetes, heart conditions, or blood-thinning agents. The coumarin in Cassia cinnamon can increase the risk of liver damage when combined with other hepatotoxic drugs like acetaminophen or statins.

Comparison of Cassia vs. Ceylon Cinnamon


Feature	Cassia Cinnamon	Ceylon Cinnamon
Common Name	"Regular" Cinnamon	"True" Cinnamon
Origin	China, Indonesia, Vietnam	Sri Lanka
Coumarin Content	High	Trace Amounts
Flavor	Strong, Pungent, Spicy	Mild, Delicate, Sweet
Cost	Less Expensive	More Expensive
Availability	Widely Available	Found in specialty stores
Health Risk	Higher risk of liver damage with large intake	Very low risk, safer for regular use

Safe Consumption Guidelines

To enjoy the flavor and potential health benefits of cinnamon while minimizing risk, it's best to follow these simple guidelines:

Choose Ceylon Cinnamon: If you plan to consume cinnamon frequently or in larger doses, switch to Ceylon cinnamon to avoid high coumarin intake.
Moderate Intake: For Cassia cinnamon, stick to moderate amounts. The U.S. Department of Agriculture suggests that half a teaspoon or less per day is generally safe for most people.
Avoid Supplements: Cinnamon supplements often contain concentrated doses and may not specify the type of cinnamon used. Always consult a healthcare professional before starting any supplement regimen.
No Dry Cinnamon: Never attempt to swallow dry cinnamon powder. This poses a significant choking and lung health risk.
Consult Your Doctor: If you take medication for diabetes, heart disease, or liver conditions, discuss your cinnamon intake with your doctor to avoid harmful interactions.

Conclusion

While a delicious and beneficial spice in moderation, there are indeed negative effects of cinnamon, especially when dealing with the high-coumarin Cassia variety. The most significant risks include liver damage from coumarin, allergic reactions, and interactions with certain medications. By being mindful of the type of cinnamon you use and moderating your intake, you can safely enjoy this popular spice without significant health concerns. For those with health conditions or who want to use cinnamon therapeutically, choosing Ceylon cinnamon and consulting a medical professional is the safest approach. For more health-related information, consider visiting the National Center for Complementary and Integrative Health website.

Frequently Asked Questions

Yes, excessive, long-term consumption of Cassia cinnamon can cause liver damage due to its high coumarin content. For this reason, individuals with pre-existing liver conditions should be especially cautious and consider using Ceylon cinnamon instead.

Yes, Ceylon cinnamon, often called 'true' cinnamon, is much safer than Cassia. It contains only trace amounts of coumarin, the compound linked to potential liver issues, making it a better option for high or regular intake.

While it's difficult to overdose, consuming too much, especially the Cassia variety, can be problematic. The primary concern is the liver toxicity associated with excessive coumarin exposure over time.

The 'cinnamon challenge' is a dangerous viral trend involving swallowing a tablespoon of dry cinnamon. This can lead to breathing problems, choking, and even permanent lung damage from irritation and inflammation.

Yes, cinnamon can interact with certain medications, including blood thinners, diabetes drugs, and those that affect the liver. You should consult your doctor if you take these medications and regularly consume cinnamon.

Cinnamon can cause allergic reactions, especially when consumed in large amounts. Symptoms may include mouth sores, swelling of the tongue or mouth, and skin rashes.

While small culinary amounts of cinnamon are likely safe during pregnancy, supplements or large doses are not recommended due to limited research and potential risks. Always consult a doctor about safe intake levels.