Tonsillitis in children is mainly caused by bacterial infections.
First, take the child's temperature.If the temperature exceeds 101.3°F (38.5°C), you need to consider using antipyretics, such as Motrin.If the temperature is below 101.3°F, physical cooling methods can generally be used, such as cold compresses.

In addition, you need to consider using antibiotics to fight the infection. Cephalosporins are commonly used.
However, these are all prescription drugs, so you need to visit a pediatrician or an otolaryngologist.
