Daughter has 2 canker sores on her tonsils at the back of throat their kind of small. plus she has 2 on the front of her mouth howl long will it last?

Canker sores: The most common observable lesions in the oral cavity. Individual ulcers typically last 7-10 days. The topical anesthetic otc application is recommended. Rec.: see your pcp if concerned.

7-10 days usually: During this time have her eat softer foods and avoid acidly foods (soda, ketchup, tomato sauce, etc.). Have her rinse with warm salt water several time a day. If it interferes with eating have her rinse (not swallow) with a mixture of malox and liquid benadryl (diphenhydramine). If other cold symptoms develop then see your pediatrician.