Tonsillitis generally results from infection with beta-hemolytic streptococci but can also result from other bacteria or viruses, such as herpesvirus, cytomegalovirus, or adenovirus.

Chronic tonsillitis may result in chronic upper airway obstruction, causing sleep apnea or sleep disturbances, cor pulmonale, failure to thrive, eating or swallowing disorders, and speech abnormalities. Febrile seizures, otitis media, cardiac valvular disease, abscesses, glomerulonephritis, subacute bacterial endocarditis, and abscessed cervical lymph nodes may also be noted. Scarlet fever, rheumatic fever, and heart disease may also occur, but these conditions are not as common as they were before the widespread use of antibiotics.

The patient with acute tonsillitis may complain of mild to severe sore throat. In a child who is too young to complain about throat pain, the parents may report that the child has stopped eating. The patient or parents also may report muscle and joint pain, chills, malaise, headache, and pain that is frequently referred to the ears. Because of excess secretions, the patient may complain of a constant urge to swallow and a constricted feeling in the back of the throat. Such discomfort usually subsides after 72 hours. Fever of 100° F (37.8° C) or higher may be present, and palpation may reveal swollen, tender lymph nodes in the submandibular area.

Inspection of the throat may reveal generalized inflammation of the pharyngeal wall, with swollen tonsils that project from between the pillars of the fauces and exude white or yellow follicles. Purulent drainage becomes apparent when pressure is applied to the tonsillar pillars. The uvula may also be edematous and inflamed.

Patients with chronic tonsillitis may report recurrent sore throats and attacks of acute tonsillitis. They may present with purulent drainage in the tonsillar crypts, foul breath, and persistently tender cervical nodes.