Mouth sores may make eating and talking painful. The most common mouth sores are cold sores and canker sores. In severe cases of canker sores, a doctor may prescribe a medicine to ease inflammation and pain.
Other possible causes of mouth sores include:
Impetigo. Symptoms may include oozing, honey-colored, crusty sores that appear on the face, usually between the upper lip and nose. Impetigo is more common in children than adults.
Hand-foot-and-mouth disease (Coxsackie virus), in children. Ulcers may appear on the inside of the cheeks and on the gums and sides of the tongue, usually lasting 2 to 3 days. These symptoms, which usually are mild, may also occur with a blister-type rash on the palms of the hands and soles of the feet. Although the mouth sores may only last 2 to 3 days, the illness may last a week.
Herpangina (Coxsackie virus). The virus most commonly occurs in the summer and autumn. It starts with a high fever, sore throat, headache, and a general feeling of illness (malaise). Usually, painful sores (ulcers) develop in the back of the mouth, especially the soft palate, within 24 to 48 hours of the fever. The illness lasts 7 to 10 days.
Medicines. Chemotherapy, sulfa drugs, phenytoin (such as Dilantin), and gold compounds are a few examples of medicines that can cause mouth sores.
Inflammation of the gum and mouth tissue (gingivostomatitis), which is common in children. A child who has gum sores and a fever or who does not feel well should be evaluated by a health professional.
Chickenpox. Chickenpox sores in the mouth look different than chickenpox on the body. In the mouth, the sores look like raised bumps (papules) and then turn into shallow ulcers. Sores on the body crust over after the blister stage, but crusting does not occur in the mouth.
Injury. Tongue ulcers may result from biting, chewing, or burning of the tongue.
Piercings. Mouth, tongue, and lip sores can be caused by the piercing itself or by irritation from the jewelry used in the piercing.
Oral cancer, which may develop in any part of the oral cavity. Your chances of getting oral cancer are increased if you smoke, use smokeless (spit) tobacco, or use alcohol excessively.
Skin diseases. Blisters in the mouth can be caused by immune system diseases, such as lichen planus, pemphigus vulgaris, pemphigoid, lupus, or erythema multiforme.