Tonsils are lymph nodes present within the folds of tissues called crypts, on each side of the throat. They function as a defense mechanism and help in fighting the infection. However, sometimes they get infected and this inflammation of the tonsils is called tonsillitis. There is no specific cause of tonsillitis but anything that causes infection in the head region can cause inflammation of the tonsils.  Tonsillitis is usually associated with underlying health conditions such as infections, tumors, and chronic cough.