A peritonsillar abscess is a pocket of pus that forms in the space around the tonsils.
A peritonsillar abscess forms when tonsillitis spreads beyond the tonsils. The infection travels into the space between the tonsil and the underlying muscle. This infection then forms a gradually enlarging abscess, or pocket of pus.
Most episodes of peritonsillar abscess follow tonsillitis, or an infection of the tonsils. These infections are usually caused by bacterial organisms called group A streptococci. Obstruction of certain glands around the mouth may also cause a peritonsillar abscess.
A person who has had peritonsillar abscess or chronic tonsillitis in the past is at a higher risk for another in the future. Peritonsillar abscesses are rare in children. They are more common in adolescents and adults.