What to Know About Canker Sores in Children

Medically Reviewed by Dan Brennan, MD on July 19, 2022
5 min read

What are canker sores? If you’ve ever had one, you probably remember exactly how it feels. These sores are small, painful ulcers that can develop in your mouth for a variety of reasons. They’re referred to as canker sores, mouth ulcers, or by their scientific name — aphthous stomatitis. 

While there are a few medical conditions that cause canker sores, most sores don’t have obvious causes. Even so, there are a few tests your child’s doctor can run if your child has repeat flare-ups of this painful condition. 

Learn more about canker sores in children, their causes, and their treatments in the following guide.

Canker sore causes aren't entirely clear, but outbreaks tend to follow patterns: Girls, for example, tend to get canker sores more often than boys do. Canker sores also usually affect teens more than kids under the age of 10, but younger children can get them too. 

Your pediatrician may not be able to confirm the exact cause of your child’s sores. Nobody really knows why they develop, but the following factors are often linked to these ulcers:

A viral infection. If your toddler or elementary schooler keeps developing canker sores, a virus might be the cause. Hand, foot, and mouth disease is a common (and very contagious) virus that affects babies, toddlers, and preschoolers. If your child has this illness, you’ll notice mouth ulcers, as well as similar spots that show up as blisters on your child’s hands and feet.

An autoimmune condition. Recurrent canker sores that don’t have an obvious cause such as a viral illness or a nutrient deficiency may be a sign of a brewing autoimmune illness. Many kids with celiac disease and inflammatory bowel conditions struggle with frequent canker sores in addition to many other symptoms like tiredness, brain fog, and joint pain.

Nutritional deficiencies. Low ferritin, a marker of the iron stored in your child’s body, is linked to recurrent mouth ulcers like canker sores. Iron deficiency is common in kids, and you might notice other signs of this deficiency like pale skin, dark circles under the eyes, and tiredness even though your child is sleeping well. 

Your child needs around 8 to 15 milligrams of iron a day depending on their weight and whether or not they’re having monthly menstrual periods. 

Having a deficiency in folic acid or vitamin B-12 is also linked to canker sores.

Food sensitivities. Certain foods can irritate the mouth in some kids and cause canker sores. The culprits here are usually highly acidic foods like chocolate, coffee, and citrus fruits that irritate the sensitive mucous membranes in your child’s mouth.

It’s important to know that canker sores are not the same as cold sores and that canker sore symptoms are not contagious. Cold sores are usually visible to a person looking at the child because they’re located around the mouth, on the lips, or near the nose. 

Canker sores, in contrast, develop within the mouth. They’re located on the soft tissues of the inside of the child’s cheeks. A child with canker sores might notice the following symptoms:

  • Spots of pain inside their cheeks or lips
  • Small, white patches with red rings around them that are only a few millimeters wide
  • A tingling sensation where new sores are starting to develop
  • New canker sores appearing before a menstrual period, when eating certain foods, or during times of stress
  • Either one sore or many at a time (but one is more common)
  • No illness symptoms like a fever or chills (though your child might have a fever if they already have a viral illness)

It’s usually pretty easy to diagnose a canker sore because they are visible to the naked eye. They’re painful, are white with a red “halo” around them, and only appear inside the mouth. 

Your child's pediatrician might prescribe a treatment for the sores without doing additional testing, but if the sores keep coming back, it might be time for blood tests or a small biopsy of a sore to learn more about what’s causing them.

Treatment. If your child frequently struggles with canker sores due to viral infections, a menstrual period, or a weakened immune system, your pediatrician can advise you on the right course of action. A doctor might recommend a special mouth wash, prescription medication, or over-the-counter treatment that will help prevent the sores from returning. 

Canker sores usually heal by themselves in a week or two, but they can be painful to live with during the healing process. If you’re looking for canker sore treatment to soothe your child’s discomfort at home, you might try giving them a liquid antacid, honey, or milk — but remember that infants younger than one year old should not eat honey for safety reasons. Give your child soft food without sharp edges and ensure that they drink enough liquids to speed up healing.

Prevention. Prevention depends upon knowing the cause of the sore. For example, if your child has an iron deficiency that your pediatrician thinks is causing their recurring canker sores, following the pediatrician’s instructions for treating the deficiency is important to prevent related health problems — including mouth sores.

Children who have canker sores might feel irritable or distracted, and they probably won’t want to eat or drink anything spicy or acidic (like spaghetti sauce or orange juice) because this can cause more pain. 

Though the canker sores will go away with treatment after about a week or two, some children have recurring sores that really bother them and affect how they eat, speak, and interact with others. 

Canker sores are a normal part of life for many healthy children. For two-thirds of children who develop them, an outbreak is a one-time occurrence. If your child is experiencing mouth pain due to recurring canker sores, it’s important to pay your pediatrician a visit to determine if there’s an underlying cause you can treat.