Canker sores, aphthous ulcers, are common, small lesions inside the mouth. These ulcers are generally shallow, round, or oval, featuring a white or yellow center surrounded by a red border of inflamed tissue. While they are not contagious and typically heal within one to two weeks, they can cause significant pain and make routine activities like eating and talking difficult. Managing the diet during an outbreak is one of the most effective ways to reduce discomfort and support the body’s natural healing process.
Foods That Cause Chemical Irritation
Highly acidic foods are among the most significant sources of irritation, directly causing a stinging or burning sensation upon contact. The open wound exposes underlying nerve endings, and the low pH of these foods irritates the sensitive tissue. Citrus fruits, including lemons, oranges, and grapefruits, should be avoided because their high acid content can exacerbate the pain and potentially delay healing.
Tomatoes and foods made with a tomato base, such as pasta sauces, ketchup, and salsa, are problematic due to their relatively high acidity. Other acidic items, like vinegar and pickled vegetables, can also cause a painful reaction when they encounter the ulcerated area. Carbonated beverages, including soda, should be avoided as well, since the dissolved carbonic acid contributes to the overall acidic environment in the mouth.
Spicy foods present a different type of chemical irritant, primarily due to the compound capsaicin found in chili peppers and hot sauces. Capsaicin activates the transient receptor potential vanilloid 1 (TRPV1) receptor, which is a pain receptor in the mouth that usually detects heat. When capsaicin binds to this receptor on the exposed nerve endings of the sore, the brain interprets the signal as a burning pain, intensifying the discomfort.
Salty foods and products containing high concentrations of certain additives can also irritate the open sore. High sodium concentrations can draw moisture out of the tissue, which causes a painful stinging sensation. Many processed foods contain flavor enhancers or preservatives that may also act as chemical irritants, sometimes triggering a painful response in susceptible individuals.
Foods That Cause Physical Damage
Beyond chemical irritation, foods with specific textures can cause physical damage to the canker sore and surrounding healthy tissue. Abrasive textures are particularly problematic because they can scrape or rub against the delicate ulcer, increasing the size of the wound or preventing the formation of a protective layer. Hard, crunchy, or sharp foods like potato chips, pretzels, crusty bread, toast, and nuts should be temporarily removed from the diet.
Popcorn, especially partially popped kernels and the hard outer shell, presents a double risk of scraping the sore and potentially lodging a sharp piece in the wound. Physical damage not only increases immediate pain but also prolongs the healing time by constantly re-injuring the area. Even seemingly innocuous foods, such as crackers or granola, can have edges sharp enough to cause friction on the mouth’s inner lining.
Temperature extremes can exacerbate the pain associated with canker sores. Extremely hot foods or beverages, like freshly brewed coffee or steaming soup, cause inflammation by increasing blood flow to the already-irritated area. While cold foods are often soothing, hot items trigger a sharp pain response.
Foods that require extensive or repetitive chewing can also cause friction on the sore, even if they are not inherently abrasive. Chewy or sticky items, like taffy or some kinds of dried fruit, force the mouth muscles and tongue to work harder, repeatedly pressing the sore against the teeth or cheek. Minimizing the need for vigorous mastication can help keep the ulcer undisturbed and allow the healing process to progress.
Bland and Healing Diet Choices
To minimize pain and encourage the healing of canker sores, selecting soft, bland, and non-acidic foods is recommended. Dairy products like plain yogurt, soft cheeses, and milk are excellent choices because they are generally low in acid and easy to swallow. The cool temperature of yogurt or cottage cheese can also provide a soothing, numbing effect on the irritated area.
Starchy, soft foods are also well-tolerated and provide calories without irritation. Examples include mashed potatoes, well-cooked pasta, oatmeal, and cream of wheat. Scrambled eggs and soft fruits, such as bananas and applesauce, are nutritious options that require little to no chewing.
Consuming cool or room-temperature foods and liquids is preferable to hot items to avoid triggering pain receptors in the inflamed tissue. Smoothies made with non-acidic fruits, such as pears or bananas, are a good way to maintain nutrient intake. Staying adequately hydrated is important, and plain, cool water is the ideal choice to keep the mouth moist and help rinse away food particles without causing irritation. It is best to avoid all carbonated drinks, fruit juices high in citric acid, and alcohol until the canker sore has fully healed.