Your child is suffering from a tonsil infection, a common malady that occurs when a virus or bacteria invades the tonsils. It can be caused by a number of factors, including colds, influenza and bacteria. Most tonsil infections are not serious and clear up on their own. However, they are often associated with strep throat, a bacterial infection that must be treated with antibiotics. Occasionally, surgery to remove the tonsils is recommended, but this is reserved for severe or recurrent cases.