What Causes Canker Sores? Triggers and Risk Factors

Canker sores are small, painful ulcers that form inside your mouth. They appear on your tongue, gums, or the inside of your cheeks and lips. While doctors do not know the exact cause, several factors can trigger these annoying sores.

Common Triggers for Canker Sores

Many things can trigger canker sores. Minor injuries to your mouth, like biting your cheek or brushing too hard, are common causes. Stress and lack of sleep also play a big role in triggering outbreaks.

Certain foods can cause problems too. Acidic fruits like oranges and tomatoes, spicy foods, and coffee are known triggers. Some people react to ingredients in their toothpaste, especially sodium lauryl sulfate.

Nutritional deficiencies can make you more likely to get canker sores. Low levels of vitamin B12, iron, folic acid, or zinc have been linked to frequent outbreaks. Hormonal changes during menstruation may also trigger sores in some women.

Are Canker Sores Contagious?

No, canker sores are not contagious. You cannot spread them to others through kissing, sharing food, or any other contact. This is one key difference between canker sores and cold sores, which are caused by a contagious virus.

Are Canker Sores Herpes?

No, canker sores are not herpes. This is a common confusion. Cold sores (fever blisters) are caused by the herpes simplex virus and appear on or around your lips. Canker sores have no viral cause and only form inside your mouth. They are completely different conditions.

How Long Do Canker Sores Last?

Most canker sores heal on their own within 1 to 2 weeks. Minor sores, which are the most common type, are usually painful for 3 to 5 days before they start to feel better. Major canker sores are less common but can take 2 to 6 weeks to heal and may leave scars.

When to See a Doctor

See your doctor if a canker sore lasts more than 2 weeks, if you get them very often, or if you have a fever with your sores. Frequent canker sores can sometimes signal an underlying health issue like celiac disease or an immune system problem.