Though most people think of canker sores as those sores that develop on the inside of the lip or cheek, they also can develop on the tonsils as well. When they develop on the inside of the cheeks, lips or gums, they're usually the result of biting or injuring the area; when they develop on the tonsils however, they usually were caused by allergies to something ingested like food, medication, or even oral hygiene products. Beside being an allergic reacting tonsil canker sores may result from poor oral hygiene.

Food allergies are one of the most common causes of canker sores on the tonsils. Foods that are often to blame for the development of this condition include strawberries, tomatoes, or other highly acidic fruits and vegetables. In addition, some types of shellfish are also linked to a high occurence of canker sores on the tonsils. Individuals who develop these types of canker sores might benefit from keeping track of what they eat and when they develop the canker sore. This sort of tracking can help identify the cause of the sore so that that particular food can be avoided. Food allergy tests can also help uncover the particular food that causes the sores.

Allergies to certain types of medications can manifest as canker sores anywhere in the mouth, including the tonsils. Again, keeping track of what medications were introduced and when these canker sores developed will help identify which particular medication caused the sore. Sometimes, antibiotics may be the culprit. If a medication is the cause of the canker sore, it's important to consult a health care professional; ceasing the drug regimen without the advice of a professional can cause other problems.

Canker sores on the tonsils in particular have also been linked to toothpaste allergies. In most cases, the allergic reaction occurs due to a specific ingredient in the toothpaste. Individuals who experience an allergic reaction to toothpaste should read the ingredient list closely. Comparing the ingredient list of an allergy-causing toothpaste with one that has not produced a reaction can help identify the canker sore causing ingredient.

In some cases, canker sores on the tonsils can be result from poor hygiene. Failure to brush one's teeth on a regular basis, for example, has been identified as a possible cause of canker sores. Brushing on a regular basis, using the right type of toothbrush, and applying appropriate amounts of pressure are all important in ensuring adequate dental hygiene.