A canker sore usually heals on its own in a matter of days, but it can be a painful inconvenience for a kid who's waiting for it to get better. The mouth ulcer often develops on the inside of the cheek or on the tongue, making eating uncomfortable. Canker sores are not contagious, unlike cold sores, which are blisters that usually appear on the lips.
Dab a mixture of equal parts water and hydrogen peroxide on the sore, and then follow with a bit of milk of magnesia. This can reduce pain and help clear up the sore, according to KidsHealth. A small amount of milk of magnesia dabbed on the sore several times a day eases pain and speeds healing, according to Blue Cross Blue Shield of Massachusetts. Applying a paste of baking soda and water directly on the sore after meals also helps.
Mouthwashes with tetracycline help reduce pain, promote healing and prevent bacterial infections in the sores, according to the National Institute of Dental and Craniofacial Research. Tetracycline requires a prescription, and it may stain the teeth of young children. KidsHealth recommends a homemade mouthwash with 2 ounces of hydrogen peroxide and 2 ounces of water or 4 ounces of water, a teaspoon of salt and a teaspoon of baking soda. Rinse the mouth four times a day. Rinsing with a cup of warm water and a half-teaspoon of salt several times a day can also help.
Medicines containing peroxide and glycerin clean and coat the sore while easing the discomfort. Medicines with benzocaine, menthol and eucalyptol can be applied repeatedly. They may cause some stinging at first but can then numb the sore and help healing. Benzocaine helps reduce the pain and duration of canker sores, according to the National Institute of Dental and Craniofacial Research.
Placing wet black tea bags on a sore can help, KidsHealth says. Black tea contains tannin, which relieves pain and is found in some medicines. Tea bags have long been used as home remedies for toothaches.
Make sure your child avoids spicy and sour foods and chips, which can irritate a canker sore, Blue Cross Blue Shield of Massachusetts advises. Your child should use a soft-bristled toothbrush and avoid toothpaste that contains sodium lauryl sulfate, which may promote sores.