Quinsy or Peritonsillar abscess is a rare but very serious complication of tonsillitis. The condition causes pus to collect and build up between the tissues of your throat and the tonsil. Pus accumulates in an infected area when a bacterial infection (tonsillitis) is untreated thereby spreading from the tonsil to the surrounding tissues in the throat. Although quinsy can occur at any age, it is most common in young adults and teenagers but rare in young children and infants. You can get quinsy more than one time in your lifetime. This condition can cause swelling and pain in the throat. In severe cases, it can lead to obstruction of the throat which could lead to difficulties while swallowing, breathing and speaking.