An allergic reaction to cinnamon can cause a wide range of symptoms, depending on the severity of the allergy and whether the cinnamon touches the skin or is ingested internally. Some of the most common symptoms include watery eyes, runny nose, and cough. Skin irritation may result in various types of dermatitis, including eczema. Swelling of the face or throat, especially if accompanied by difficulty breathing, may indicate the presence of a severe and potentially life-threatening allergic reaction known as anaphylaxis. Any questions or concerns about possible signs of an allergic reaction to cinnamon should be discussed with a doctor or other medical professional.

In many cases, an allergic reaction to cinnamon is so subtle that it may be confused with other problems, such as the common cold or seasonal allergies. This is especially true when cinnamon is an added ingredient in a product, because the affected person may not even realize that cinnamon has been consumed. Itchy, watery eyes and a stuffy or runny nose are commonly reported signs of an allergic reaction to cinnamon and usually begin within a matter of seconds or minutes following contact with cinnamon. Cough, a mild fever, or a sore throat may also be present. Those with underlying respiratory illnesses such as asthma may notice a worsening of symptoms after coming into contact with cinnamon.

Sometimes, an allergic reaction to cinnamon may manifest in the form of skin irritation, medically known as dermatitis. This often involves a condition known as eczema, in which the skin may itch, peel, or develop blisters that break open. This type of reaction is most common when cinnamon comes into contact with the skin, although those with a relatively mild allergy may develop skin symptoms if cinnamon is repeatedly ingested.

Anaphylaxis may occur during an allergic reaction to cinnamon, although this is not common. Symptoms of this severe type of allergic reaction may include swelling of the face, tongue, or throat as well as difficulty breathing. When breathing becomes difficult, there is a risk of oxygen deprivation to the brain and other organs of the body. This lack of oxygen can cause permanent brain damage or even death within a matter of minutes, making it crucial to obtain emergency medical assistance at the first sign of these symptoms. Life support measures such as oxygen therapy may be necessary, and hospitalization is likely until the health of the patient has stabilized.