Mouth Sores

Sores commonly develop on the lips and inside the mouth. These sores may be painful or bothersome, but most are harmless. Occasionally, they result from a serious disorder. Any sore that is present for more than 3 to 4 weeks should be evaluated by a dentist or doctor.

Cold sores: The most common sore on the lips is a cold sore (herpes labialis). Cold sores are caused by a viral infection. Exposure to sunlight or cold can trigger a cold sore. Cold sores are small and filled with fluid. Often, they occur in clusters. Typically, cold sores appear on the lips and reappear in the same place. Often, an area of the lips tingles or burns before the sore develops. The sore forms a crust, then disappears after 5 to 7 days. A prescription drug used immediately after the tingling is felt can make the sore disappear more quickly. Some of these drugs, such as penciclovir, are applied to the lips. Some, such as valacyclovir or acyclovir, are taken by mouth.

Canker sores: The most common sore inside the mouth is a canker sore (aphthous stomatitis). Canker sores are more likely to develop during stress or illness. They are white, flat, and surrounded by a red area. They can be painful. Many are round, but sores may be irregularly shaped. They usually last 7 to 10 days and heal without a scar. They often recur. Prescription drugs that resemble corticosteroids, such as triamcinolone, or anesthetics, such as lidocaine or benzocaine, can be applied to the sores to help them heal.

Thrush: Thrush (candidiasis) is a fungal infection. It tends to develop in the mouth in people who take antibiotics or have a dry mouth. Thrush often appears as a white, curdlike film coating the gums, including the gums under dentures, and the inside of the mouth. Thrush is usually painless, although the affected areas sometimes appear red and burn. Thrush may also affect the corners of the mouth, which become cracked, red, and dry. Antifungal creams and rinses are effective in most cases. When thrush is severe, antifungal drugs may be taken by mouth.

Oral cancer: Oral cancer starts as a red or white sore on the lips or mouth. The sores may or may not be painful. They do not heal and gradually get larger. Any red or white sore that does not heal after 3 to 4 weeks should be checked by a dentist or doctor because it may be an early sign of cancer. A biopsy, culture, x-ray, or blood test may be done to check for oral cancer or another disorder.

Other sores: Other disorders can cause sores that resemble those due to oral cancer. Lupus (systemic lupus erythematosus), a disorder in which the immune system malfunctions, causes mouth sores that are usually painless. They are a mixture of red and white sores that can occur on the tongue, inside of the cheeks, roof of the mouth, and gums. Lichen planus, a skin disorder that causes itching and a rash, causes mouth sores that are usually painless. They are bluish white and flat with an irregular shape that can resemble a spider's web. If lupus, lichen planus, or another disorder causes sores near the back of the mouth, eating and swallowing become difficult. Because these sores are difficult to distinguish from oral cancer, they should be checked by a dentist or doctor.