What causes quinsy

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Last updated: April 4, 2026

Quick Answer: Quinsy, also known as a peritonsillar abscess, is an infection that causes a collection of pus to form behind the tonsil. It typically develops as a complication of untreated or inadequately treated tonsillitis (strep throat). The bacteria responsible, most commonly Streptococcus pyogenes, spread from the tonsil tissue into the surrounding space.

Key Facts

Overview

Quinsy, medically termed a peritonsillar abscess, is a serious complication that can arise from tonsillitis. Tonsillitis itself is an inflammation of the tonsils, commonly caused by viral or bacterial infections. When bacterial tonsillitis, particularly that caused by the bacterium Streptococcus pyogenes (group A Streptococcus), is not effectively treated or if the infection progresses, it can lead to the formation of an abscess. This abscess is essentially a localized collection of pus that develops in the tissues surrounding one of the tonsils, pushing it inward towards the center of the throat.

What is a Peritonsillar Abscess (Quinsy)?

A peritonsillar abscess is a painful collection of pus located just outside the tonsillar capsule, in the space between the tonsil and the muscles of the pharynx. This space is known as the peritonsillar space. The infection originates in the tonsil tissue and then spreads into this adjacent area, leading to inflammation, swelling, and the formation of an abscess. While often a complication of tonsillitis, it can sometimes arise from other throat infections or even dental infections.

Causes of Quinsy

The primary cause of quinsy is a bacterial infection, most frequently caused by Streptococcus pyogenes, the same bacterium responsible for strep throat. When tonsillitis, especially strep throat, is not adequately treated with antibiotics, or if the infection is particularly aggressive, the bacteria can penetrate deeper into the tissues surrounding the tonsil. This invasion leads to an inflammatory response and the formation of a pocket of pus.

Factors that can increase the risk of developing quinsy include:

How Does Tonsillitis Lead to Quinsy?

Tonsillitis involves inflammation and infection of the tonsils. The tonsils are lymphoid tissues located at the back of the throat. When bacteria, such as Streptococcus pyogenes, infect the tonsils, they can cause symptoms like sore throat, fever, and difficulty swallowing. If this infection is not fully eradicated by the immune system or antibiotic treatment, the bacteria can spread from the tonsillar tissue into the surrounding connective tissue and lymphatic channels within the peritonsillar space. This invasion triggers an intense inflammatory response, characterized by the accumulation of white blood cells, dead tissue, and bacteria, forming a collection of pus – the abscess.

Symptoms of Quinsy

The symptoms of quinsy typically develop rapidly over a few days and can be quite severe. They often begin with a worsening sore throat, which may initially be mistaken for persistent tonsillitis. Key symptoms include:

Diagnosis and Treatment

Diagnosing quinsy typically involves a physical examination of the throat, where a doctor can often see the swollen tonsil and the bulging abscess. A needle aspiration of the affected area may be performed to confirm the presence of pus and identify the bacteria. Treatment is essential and usually involves:

In recurrent cases or if tonsils are frequently infected, a tonsillectomy (surgical removal of the tonsils) may be recommended after the abscess has healed.

When to Seek Medical Attention

If you experience severe sore throat, difficulty swallowing, fever, or a muffled voice, especially if symptoms worsen rapidly or are on one side of your throat, it is crucial to seek immediate medical attention. Prompt diagnosis and treatment are vital to prevent complications such as airway obstruction, spread of infection to deeper tissues, or sepsis.

Sources

  1. Peritonsillar abscess - WikipediaCC-BY-SA-4.0
  2. Quinsy - NHSfair-use
  3. Peritonsillar abscess - Symptoms and causes - Mayo Clinicfair-use

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