Tonsillitis is an infection of the tonsils that causes inflammation. It's most common in children aged 3 to 7, who have larger tonsils than adults and older children. The tonsils are made of lymphatic tissue. Their job is to produce antibodies that fight infection. Ironically, such tissue is quite prone to becoming infected itself. Tonsillitis can be caused by viral or bacterial infections.
Many cases of tonsillitis never reach the doctor's office, but it is estimated that 15% of all visits to family doctors are because of tonsillitis.
Tonsillectomy (tonsil removal) has always been the most common childhood operation, but it is considered a last resort for tonsillitis these days.