Canker Sores- What are they, and why does my child get them?

Also known as aphthous ulcers, canker sores are small sores that can occur inside the mouth, cheeks, lips, throat, or sometimes on the tongue. Canker sores shouldn’t be confused, however, 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.

At a different time we will certainly discuss all issues concerning sores that are caused by the herpes simplex virus. However, if your child was diagnosed by your pediatric dentist or pediatrician with canker sores, you should definitely read the following.

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. If both parents are prone, unfortunately your child is even more prone. Although we don’t know exactly what causes canker sores, many factors are thought to put your child at risk.

Diet may be a factor. Children who have nutritional deficiencies of folic acid, vitamin B12, and iron seem to develop canker sores more often. Also, children with some food allergies are prone as well. Canker sores may also indicate that a child 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. It’s always hard to imagine what kind of stress your three or four year old child may have; however, little stress can also go a long way with young children.  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 those most often, and females are twice as likely to develop them as males. Some girls and women find that they get canker sores at the start of their menstrual periods.

What are the signs and symptoms of canker sores?

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 popup 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.

How are canker sores diagnosed?

Canker sores are usually diagnosed by visual inspection by your pediatric dentist or pediatrician.  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.

Are canker sores preventable?

Mouth sores cannot be prevented, but the first line of defense against canker sores in children is to manage their oral environment to reduce the risk of developing these painful sores. Help your child maintain good oral hygiene. Help young children brush and teach growing children how to brush thoroughly and effectively.  Your child’s pediatric dentist will be able to best equip your child for good oral health for life.

  • Avoid buying toothpaste that contains sodium lauryl sulfate because it is known to cause canker sores.
  • Allow young children to use plastic utensils to help prevent mouth sores caused by injuries to the mouth.
  • Avoid feeding your child rough or acidic foods that may irritate the delicate inside of their mouth.
  • If your child has recurrent canker sores, discuss diet and medications with your pediatrician to identify any food or drugs that may be causing an allergic reaction.
  • Encourage children to eat yogurt, which contains acidophilus and may help prevent or encourage the healing of mouth sores.

How do I treat my child’s canker sores?

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. You can also try to apply a wet black tea bag 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.

Kaufman Children’s Dental Hospital


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