Canker Sores (Aphthous Ulcers)

Canker sores, or aphthous (AF-thus) ulcers, are small, round sores in the mouth that quickly turn white and usually are painful.


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Aphthous ulcers

Oral inflammation


Ashley's Story

Ashley first noticed a slight tingle in her mouth one morning as she was brushing her teeth before school. It was inside her lower lip, on the soft, fleshy part in front of her bottom teeth. By the next morning, she felt a bump that hurt when her tongue touched it and when she tried to drink orange juice with her breakfast. By dinner time, when Ashley pulled down her lip (gently) to look at the small, round blister in her mouth, she saw that it was white and rimmed with a red ring that looked like a halo. It was Ashley's first canker sore, but it probably would not be her last.

What Is a Canker Sore?

Canker sores are small, round sores that are found where Ashley discovered hers: inside the mouth. They may occur on the inside of the lips, on the tongue, on the roof or floor of the mouth, or inside the cheeks. They may appear as one small sore or in groups, and they can be quite irritating and painful to even the slightest touch. Contact with acidic, salty, or spicy foods and fluids, like chips or orange juice, can be particularly painful for people with canker sores.

Canker sores are not contagious * . They cannot be passed along from one person to another by kissing or by sharing food. It is important, however, to distinguish canker sores from other kinds of mouth sores, which may be caused by viral infections * , trauma, vitamin deficiencies, and sometimes, but not often, cancer. If a mouth sore has not healed within a week or two, it is important to see a doctor.

What Causes Canker Sores?

No one is sure what causes canker sores, although they occur more frequently when people are experiencing stress. Often, the first sores appear as children near middle school age. Canker sores are more common among women.

How Are Canker Sores Treated?

Ashley's canker sore disappeared on its own two weeks after she first noticed that sore feeling inside her mouth. Most canker sores clear up the same way, without treatment, although some people use over-the-counter medications to numb canker sores during the first four or five days when they are most painful. It also helps to avoid the sore while brushing teeth and to cut out foods that aggravate the pain, such as salty chips, citrus fruits, or spicy foods.

If canker sores recur or return, or if they do not heal on their own within two weeks, they may need to be seen by a doctor or dentist. But usually, canker sores go away on their own.

* contagious means transmittable from one person to another.

* viral infections cause mouth sores that are called fever blisters or cold sores. These are often caused by the herpesvirus, and they usually appear on the gums or around the mouth and lips. Unlike canker sores, fever blisters and cold sores are contagious.

See also


U.S. National Institute of Dental Research (NIDR), Building 31, Room 2C35, 31 Center Drive, MSC 2290, Bethesda, MD 20892-2290. The U.S. National Institute of Dental Research publishes information about canker sores, fever blisters, and mouth care.

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