The tonsils lie within folds of tissue (crypts) on either side of the throat. The tonsils perform immune functions, helping to fight infection in the head region. Tonsillitis refers to inflammation of the tonsils; however, it does not refer to a specific cause. Anything that causes inflammation and/or infection in the head region may cause activation and enlargement of the tonsils. Tonsillitis rarely occurs without an underlying cause such as viral, bacterial, and fungal infections, tumors, chronic cough, and periodontal disease.