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Canker Sores

About 1 in 5 people regularly gets bothersome canker sores, which can make eating, drinking, and even brushing teeth a real pain. But just because they're relatively common doesn't mean these small open sores inside the mouth should be ignored.

About Canker Sores

Also known as aphthous ulcers, canker sores are small sores that can occur inside the mouth, cheeks, lips, throat, or sometimes on the tongue. But don't confuse canker sores with cold sores or fever blisters, which are sores that are caused by the herpes simplex virus and are found outside the mouth around the lips, on the cheeks or chin, or inside the nostrils. Whereas cold sores are contagious, canker sores are not contagious — so kissing cannot spread them.

Although canker sores aren't contagious, the tendency to have outbreaks of canker sores can run in a family. If you're prone to canker sores, your child has a 90% chance of getting them as well.

Although no one knows exactly what causes canker sores, many factors are thought to put a person at risk. Diet may be a factor. People who have nutritional deficiencies of folic acid, vitamin B12, and iron seem to develop canker sores more often, as do people who have food allergies. Canker sores may also indicate that a person has an immune system problem.

Mouth injuries, such as biting the inside of your lip or even brushing too hard and damaging the delicate lining inside the mouth, also seem to bring on canker sores. Even emotional stress seems to be a factor. One study of college students showed that they had more canker sores during stressful periods, such as around exam time, than they did during less stressful times, such as summer break.

Although anyone can get them, young people in their teens and early twenties seem to get them most often, and women are twice as likely to develop them as men. Some girls and women find that they get canker sores at the start of their menstrual periods.

Signs and Symptoms

Canker sores usually appear as painful, red spots that can be up to 1 inch (2.5 centimeters) across, although most of them are much smaller. Sometimes the area will tingle or burn before a spot actually appears. Once it does, the canker sore may swell and burst in about a day. The open sore may then have a white or yellowish coating over it as well as a red "halo" around it. Most often, canker sores pop up alone, but they can also occur in small clusters.

Although uncommon, canker sores can be accompanied by such symptoms as fever, swollen lymph nodes, and a lethargic or slightly ill feeling.

It takes about 2 weeks for canker sores to heal. During this time, the sores can be painful, although the first 3 to 4 days are usually the worst.

If your child develops canker sores that last longer than 2 weeks or is unable to eat or drink because of the pain, contact your doctor. Also call the doctor if the sores appear more than two or three times a year.


If your child has recurrent canker sores, the doctor may want to perform tests to look for possible nutritional deficiencies (which can be corrected with dietary changes or using prescription vitamin supplements), immune system deficiencies, and food or other allergies.


Often, canker sores can be easily treated with over-the-counter or even home remedies. Carbamide peroxide is a combination of peroxide and glycerin that cleans out the sore while coating it to protect the wound.

Many over-the-counter remedies have benzocaine, menthol, and eucalyptol in them. These may sting at first and need to be applied repeatedly, but they can reduce pain and shorten the duration of the sore.

You can also have your child rinse his or her mouth with a homemade solution for about a minute, four times a day, as needed. It's extremely important to remember, though, that these rinses should not be swallowed, so they shouldn't be used in kids too young to understand not to swallow.

You can try these rinse recipes:

  • 2 ounces (59 milliliters) of hydrogen peroxide and 2 ounces (59 milliliters) of water
  • 4 ounces (118 milliliters) of water mixed with 1 teaspoon (5 milliliters) of salt and 1 teaspoon (5 milliliters) of baking soda

Another option to help reduce discomfort and speed healing is dabbing a mixture of equal parts water and hydrogen peroxide directly on the sore, followed by a bit of milk of magnesia.

Some doctors suggest applying wet black tea bags to the sore. Black tea contains tannin, an astringent that can help relieve pain. You can also get tannin in over-the-counter medications. Ask the pharmacist for more information.

If the doctor prescribes a medicine that should be applied directly to the canker sore, first dry the area with a tissue. Use a cotton swab to apply a small amount of the medication. Finally, have your child avoid eating or drinking for at least 30 minutes to make sure that the medicine isn't immediately washed away and has time to work.

In some cases of severe mouth sores, the doctor may prescribe immunosuppressive drugs or mouth rinses or gels that contain steroids.

Caring for Your Child

Help make canker sores less painful and prevent them from recurring by encouraging your child to:

  • avoid eating abrasive foods, such as potato chips and nuts, which can irritate gums and other delicate mouth tissues
  • try brushing and rinsing with toothpastes and mouthwashes that do not contain SLS
  • use only soft-bristle toothbrushes and be careful not to brush too hard
  • avoid any foods he or she is allergic to
  • avoid spicy, salty, and acidic foods (such as lemons and tomatoes), which can aggravate tender mouth sores

Although they can certainly be a pain, in most cases, canker sores aren't a huge problem. Many people have learned to deal with them — and your child can, too.

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