Tonsillitis is an inflammation of the tonsils, the two lymphoid tissues located at the back of the throat that help fight infections. It is commonly caused by viral or bacterial infections and can occur at any age, though it is more frequent in children. Symptoms typically include a sore throat, difficulty swallowing, swollen and red tonsils, white or yellow patches on the tonsils, fever, swollen lymph nodes in the neck, and sometimes bad breath. Recurrent or severe tonsillitis can lead to complications such as peritonsillar abscess or chronic throat discomfort. Because the symptoms can resemble other throat infections, medical evaluation is often needed to determine the underlying cause.