A peritonsillar abscess is a bacterial infection that usually begins as a complication of untreated strep throat or tonsillitis. A pus-filled pocket forms near one of your tonsils. It can cause pain ...

Blocked airway. Mucus can form behind a tumor or foreign object in your windpipe and cause an abscess. If bacteria get into the mucus, the blockage stops you from coughing it out. Blood-borne causes.