Tonsillitis is an inflammation or infection of the tonsils, which are lymph glands located in the throat that help fight bacteria and viruses. Common causes are streptococcus bacteria and various viruses. Symptoms include sore throat, difficulty swallowing, and fever. Diagnosis involves examination of swollen tonsils and testing of throat secretions. Complications can include abscesses, but tonsillitis is usually treated with antibiotics, acetaminophen, and ibuprofen. Repeated cases may require tonsil removal. Prevention involves avoiding sick people and practicing good hand hygiene.