12 Side Effects of Cinnamon

Those who take cinnamon daily for dieting or other health reasons should switch to Ceylon cinnamon, which contains only 0.03–0.04% coumarin. Other types of cinnamon contain much higher levels (about 0.4–0.8%) of coumarin, which can lead to liver damage if consumed daily or in high doses. In fact, Cassia cinnamon was even banned in parts of Europe for a time due to its effects on the liver. Cassia cinnamon also contains higher levels of compounds such as styrene, benzene, 1,1′-(2-butene-1,4-diyl)bis-, benzene, 1,1′-(1,2-cyclobutanediyl)bis-, palmitic acid, stearic acid, 4-phenylbutyl chloride, and (2,3-diphenylcyclopropyl) methyl phenyl sulfoxide—substances found in only negligible amounts in Ceylon cinnamon (Rush University).

Cinnamon may also lower your blood sugar levels, depending on the amount you consume. While taking 2 teaspoons of Ceylon cinnamon powder or boiling a cinnamon stick into tea may not have a significant effect, Ceylon cinnamon bark oil can cause a dramatic drop in blood sugar, potentially leaving you lightheaded and a bit woozy—especially if you're also taking medication. So, be cautious.

If you add more than 2–3 drops of Ceylon cinnamon bark oil to your tea or coffee, you might feel lightheaded. However, the flavor it adds is incredible when used in moderation—probably one of the reasons Coca-Cola uses Ceylon cinnamon bark in its formula, even though it's loaded with sugar.

Pregnant women should avoid taking cinnamon. This is because cinnamon—especially its essential oils—can induce premature labor or cause uterine contractions. While cinnamon may help with stomach pain, gas, or indigestion, it shouldnotbe used for these purposes during pregnancy. It's better to be safe than sorry. An occasional cup of cinnamon tea is probably harmless, but why take the risk? Taking cinnamon tablets—or especially inhaling cinnamon oil—should be avoided entirely.

Cinnamon is believed to have blood-thinning properties. These effects are particularly strong in Cassia cinnamon, while Ceylon cinnamon does not appear to have the same impact. The blood-thinning effect of Cassia cinnamon may help it act as a natural anti-clotting agent, which can be beneficial for those with heart disease.

However, caution is advised: cinnamon should not be taken alongside blood-thinning medications (also known as anticoagulants, or medications that prevent blood clots from forming or growing). This is one reason doctors often advise against using cinnamon supplements while on such medications.

If you touch cinnamon oil without diluting it, it can irritate your skin and cause a burning sensation—similar to the effect of chili powder. This reaction can be especially severe if you accidentally touch sensitive areas, such as the genitals, after handling undiluted cinnamon oil. It's best to wear gloves or take extra care not to get it on your hands.

High doses of cinnamon may be dangerous for individuals with heart conditions, as cinnamon is known to increase heart rate. Similarly, undiluted cinnamon oil can cause a rapid heartbeat, especially in children. Remember, cinnamon oil is highly concentrated and should be diluted to less than 2% before use. At that level, it is generally considered safe for most people

A small minority of people may be allergic to cinnamon, even if they have consumed it previously without any ill effects. Symptoms usually include a runny nose, watery or sore eyes, shortness of breath (often triggered by inhaling cinnamon oil), upset stomach, facial or hand swelling, anaphylactic shock (including irregular heartbeat, dizziness, confusion, or a sudden drop in blood pressure), and nausea.

Most of the time, cinnamon allergies are not life-threatening. While adults are more commonly affected, young children—especially infants and toddlers—may also develop a reaction, sometimes as a result of the mother consuming cinnamon. If you suspect a cinnamon allergy, stop consuming it and remove all traces from your home. Cinnamon is found in many foods, so be sure to check that anything you eat does not contain it—particularly Cassia cinnamon. An allergy test should determine which type of cinnamon you are sensitive to, so appropriate treatment can be provided.

Because cinnamon can act like a natural antibiotic in many ways, taking commercial antibiotics alongside cinnamon may create a conflict—similar to taking a double dose of antibiotics. It is best to stop taking cinnamon when you are on prescription antibiotics and to consult your doctor. The FDA states that cinnamon has no proven health benefits. If that is the case, why isn’t it allowed to be marketed as a drug?

Traditional Chinese medicine advises avoiding anything that increases body heat when necessary. Cinnamon, like alcohol, black pepper, cayenne pepper, cauliflower, lobster, coffee, garlic, ginger, glutinous rice, kimchi, onions, and pumpkin, may increase body heat. As body heat or inflammation rises from consuming too much cinnamon, the body attempts to release the excess heat. This usually manifests as boils under the tongue, cracked lips, pimples, or thick, crusty mucus seeping from the eyes. You may not notice this as much in winter, but during summer it can be more pronounced if you consume too much cinnamon. For example, if you are going through menopause, you should avoid cinnamon. Likewise, if you have recently eaten a large amount of lobster, it’s best not to eat cinnamon.

Lately, teens and even preteens have been playing a dangerous game of seeing who can swallow a tablespoon or more of cinnamon powder. Swallowing cinnamon powder without water poses a serious choking hazard that could be fatal. The powder can also enter your lungs, leading to a severe chest infection and major breathing complications. In some cases, this can cause lung collapse, which is life-threatening—especially if ventilator support is not available. Additionally, inhaling cinnamon powder can scar the lungs, resulting in long-term medical issues. In fact, any powder—not just cinnamon—can cause these serious complications.

If you touch cinnamon oil without diluting it, it can irritate your skin and cause a burning sensation—similar to the effect of chili powder. This reaction can be especially severe if you accidentally touch sensitive areas, such as the genitals, after handling undiluted cinnamon oil. It's best to wear gloves or take extra care not to get it on your hands.

We do not believe cinnamon tablets or capsules are safe or effective to take, largely due to ingredients like silicon dioxide used in their manufacture. Click here to see our in-depth look at the dangers of cinnamon capsules.