canker sore

canker sore, a small, painful ulcer of the oral cavity, typically round, shallow, and white in appearance and occurring on soft tissues, such as the inner surface of the cheek or lip, beneath or on the surface of the tongue, or on the soft palate. They are surrounded by an inflamed area and may reach 1 inch (2.5 cm) in size.

Canker sores are often preceded by a burning or tingling sensation, and once formed, they may cause significant discomfort, particularly when eating, drinking, or speaking. The discomfort may be exacerbated by contact with certain foods, including spicy foods, such as those made with hot sauces; acidic foods, such as citrus; or crunchy or hard foods, such as crackers or pretzels. The most severe cases may interfere with eating and speech.

Canker sores vary in size and severity and are generally classified into three types: minor aphthous, major aphthous, and herpetiform ulcers. Minor aphthous ulcers are small lesions, measuring less than 0.39 inch (1 cm) in diameter, that typically heal within 7 to 14 days without scarring. Major aphthous ulcers are deeper and larger, typically exceeding 0.24 inch (6 mm); they can persist for weeks or months and may leave a scar upon healing. Herpetiform ulcers, which occur as numerous small, superficial ulcers, appear simultaneously in clusters; the clusters may merge to form larger, irregular lesions.

As much as half the global population may develop canker sores at some time. The cause of the sores remains unknown, although scientists suspect that an immune reaction is involved. No permanent cure is known either, and canker sores usually heal by themselves. Local anesthetic agents and anti-inflammatory drugs may provide partial relief from discomfort.