Tonsillitis is inflammation of the tonsils, two oval-shaped pads of tissue at the back of the throat — one tonsil on each side. It's usually caused by a viral infection or, less commonly, a bacterial infection.

It's a common type of infection in children, although it can sometimes affect adults. It's a common type of infection in children, although it can sometimes affect adults.

The tonsils are two small glands that sit on either side of the throat. In young children, they help to fight germs and act as a barrier against infection.

When the tonsils become infected, they isolate the infection and stop it spreading further into the body. As a child's immune system develops and gets stronger, the tonsils become less important and usually shrink. In most people, the body is able to fight infection without the tonsils