Triggers of Canker Sores

5 Common Triggers for Canker Sores

While canker sores are usually not serious, they can be a real nuisance. A canker sore is essentially a small and shallow ulcer that erupts inside our lips or around the oral cavity, and while a specific, definite cause is still uncertain, we do understand that there are several triggers for them. If you know the triggers to watch for, it can go a long way to preventing these nasty little visitors from rearing their ugly heads in the first place. Here are five of the most common triggers to be aware of:


One of the most common triggers for canker sores is mental or emotional stress. Being in a state of stress can weaken your immune system, making you more vulnerable to the formation of sores. A different form of stress physical stress on the tissues of your mouth—can also contribute to them.


Anything that bruises or damages the tissues in your mouth can be a trigger for canker sores. Sometimes, damage is caused by braces or mouth guards rubbing against tissues. It can also be the result of using harsh mouthwashes or oral products. Tissue damage can even be caused by rough brushing. Any small cuts or scrapes in your mouth can cause canker sores to form, so avoid chewing on pens and other foreign objects, or eating particularly rough foods.

Illness or Poor Immune System

Any infection in your body can leave you more prone to canker sores. In addition, if your immune system is compromised (by short-term illness or a long-term condition) you are more likely to develop them as well.

Highly Acidic Foods and Nutritional Deficiencies

Pineapples, lemons, strawberries, tomatoes, sour candies, and other highly-acidic foods can all trigger canker sores to form, or worsen those that have already formed. Their high acid content can irritate and enflame tissues that are already under stress. If you’re prone to canker sores already, or feel one coming one, stay away from these for the time being. In addition, nutritional deficiencies can also trigger canker sores to form, particularly with regards to iron, folic acid, and zinc. In children, a B-12 deficiency is often to blame for triggering a canker sore flare-up. Calcium deficiencies can worsen existing canker sores.

Dental Appliances

Ill-fitting dental appliances, such as braces, dentures, or mouth guards, can rub against the delicate tissues inside your mouth. As a result, the irritation from these appliances is often responsible for the formation of painful canker sores. In the case of mouth guards or dentures, adjustments can be made to make them fit better. If braces are the culprit, applying dental wax to the area that’s causing irritation can help keep it at bay.

If canker sores are a regular problem for you, be sure you are using a soft-bristled toothbrush and that you aren’t heavy-handed while brushing. Try to find a toothpaste that doesn’t contain sodium lauryl sulfate. Avoid foods that tend to trigger or worsen them, and rinse frequently with salt water.

To learn more, visit Dr. Terry Brewick, DDS and his committed team at:

Dr.Terry Brewick, DDS helps patients in the Governor’s Park neighborhood of Denver, Colorado.