Canker sores

My baby has a sore inside his mouth that seems to bother him when he's eating. Could it be a canker sore?

Canker sores, also called mouth ulcers, are rare in babies. In fact, they're rare in children under 10, but it's possible that this is what's causing your baby's discomfort.

A canker sore is a roundish white or yellow open sore surrounded by a red halo. Canker sores usually appear inside the cheeks or lips, as well as on the tongue, gums, and soft palate (the soft tissue around and behind the hard roof of the mouth). They usually appear individually but can also show up in small clusters.

© Dr. P. Marazzi / Science Source

Canker sores aren't serious, but they can be painful, especially when your baby is eating or drinking or when they're touched.

What causes canker sores?

It's not really clear what causes canker sores. They tend to run in families, so they appear to have a genetic link. Some people are prone to getting sores when they're under stress.

Canker sores can also appear after a trauma to the mouth, such as a break in the skin caused by a dental procedure or by biting the tongue or cheek. There's some evidence that food allergies, viral infections, and dietary deficiencies (in particular, not getting enough iron, folic acid, zinc, or B12) can trigger canker sores.

Is a canker sore the same as a cold sore?

No, canker sores and cold sores (or fever blisters) are two different things. Canker sores are not contagious, and they appear in the soft tissues of the mouth. Cold sores (caused by the herpes simplex virus) are contagious and generally appear on the outside of the lips.

How should I treat a canker sore?

Canker sores almost always go away on their own, usually in a week to ten days (although large ones can take longer). The pain often subsides in three or four days.

In the meantime, you might want to apply ice to the sore to help numb the area. If your baby's eating solid food, cold or frozen foods – such as ice pops – may also do the trick. But don't give him hot, spicy food or citrus, which could make his mouth hurt more.

You might try a teething gel or cream, but apply it carefully – touching the sore can hurt. For a home remedy, combine 1 part hydrogen peroxide and 1 part water. Dab (gently!) on the canker sore with a cotton swab. Follow by dabbing on a little milk of magnesia. Do this three or four times a day to soothe the area and help it heal.

If your baby seems really uncomfortable, ask his doctor about giving him the proper dose of an over-the-counter pain reliever, like acetaminophen or ibuprofen. (Never give your baby aspirin, which can trigger a rare but deadly disease called Reye's syndrome in children with a viral illness.)

Should I take my baby to the doctor if he has a canker sore?

If you're not sure whether your baby's sore is a canker sore or it lasts longer than a couple of weeks, take him to the doctor for a diagnosis.

Also talk with his doctor if your baby has any other symptoms – like a rash, swollen lymph nodes, or a fever – or if the sore makes it difficult for your baby to drink adequate amounts of liquid. Talk with the doctor if your baby seems to be getting canker sores frequently, too.