Tonsillitis is inflammation (swelling) of the tonsils.
The tonsils are lymph nodes in the back of the mouth and top of the throat. They help to filter out bacteria and other germs to prevent infection in the body.
A bacterial or viral infection can cause tonsillitis. Strep throat is a common cause.
The infection may also be seen in other parts of the throat. One such infection is called pharyngitis.
Tonsillitis is very common in children.