Canker sores (aphthous ulcers) are frequent lesions that develop inside the mouth. These painful, shallow sores are typically round or oval, presenting with a white or yellowish center and a distinct red border. Unlike cold sores, which are caused by the contagious herpes simplex virus, canker sores are not infectious and cannot be spread. Understanding the nature of these non-contagious oral sores helps determine what might be causing pain deep within the throat.
Where True Canker Sores Appear
Canker sores have a specific preference for the type of tissue they affect. They almost exclusively develop on non-keratinized mucous membranes, which are the soft, movable tissues inside the mouth. This includes the inner surfaces of the cheeks and lips, the floor of the mouth, and the underside of the tongue.
The tissue lining the throat (pharynx) is mostly separate from these typical locations. While a canker sore may occasionally form far back on the soft palate, close to the throat, it is uncommon for a true aphthous ulcer to manifest on the tonsils or in the deeper pharyngeal region. If a painful sore is clearly located deep in the throat, it is likely caused by a different underlying condition.
Common Triggers for Canker Sores
The precise cause of canker sores is not fully understood, but their appearance is linked to several factors. Physical trauma to the mouth lining is a common trigger, such as accidentally biting the cheek, injury from aggressive toothbrushing, or irritation from dental devices. Stress and fatigue are also frequently reported to precede an outbreak, suggesting a connection to immune system fluctuations.
Dietary sensitivities may play a role, with acidic foods like citrus fruits, tomatoes, and spicy items potentially initiating or worsening a sore. A deficiency in specific micronutrients, particularly vitamin B12, folate, or iron, has been identified in some people who experience recurrent canker sores. Avoiding toothpastes that contain sodium lauryl sulfate (SLS) may also help reduce the frequency of outbreaks.
Other Causes of Painful Throat Sores
If a sore is felt deep inside the throat, the cause is often not a classic canker sore but a result of other infections or irritations. Viral infections frequently cause ulcers on the soft palate and pharynx, such as Herpangina or Hand, Foot, and Mouth Disease (caused by Coxsackievirus). These viral sores often appear suddenly, may be accompanied by fever, and present as small, blister-like lesions before rupturing into ulcers.
Another common source of throat irritation is gastroesophageal reflux disease (GERD), where stomach acid washes back up into the esophagus and throat. This acid exposure can damage the mucosal lining, resulting in inflammation or ulceration that causes a persistent sore throat sensation. Strep throat, a bacterial infection, typically presents as intense throat pain and swollen tonsils with white patches or pus, but it does not usually cause the distinct, circular ulcers characteristic of a canker sore. Primary Herpetic Gingivostomatitis, often seen in children, is a viral condition that can cause widespread, painful ulcers throughout the mouth and throat.
Managing Pain and Promoting Healing
For most non-severe oral ulcers, the goal of management is to relieve pain and encourage natural healing. Over-the-counter topical anesthetics containing ingredients like benzocaine or lidocaine can be applied directly to the sore to temporarily numb the area before eating or speaking. Rinsing the mouth several times a day with a warm saltwater solution or a mixture of baking soda and water can also help soothe the irritation.
Avoid foods that might mechanically or chemically irritate the sore, such as crunchy chips, abrasive breads, or highly acidic juices and spices. Most minor ulcers will resolve completely within one to two weeks without intervention. If a sore is large, causes difficulty swallowing or breathing, is accompanied by a fever, or lasts longer than two weeks, seeking medical attention is recommended to rule out a more serious underlying condition.