Part of the TeachMe Series


star star star star star
based on 16 ratings

Last updated: May 16, 2020
Revisions: 10

Last updated: May 16, 2020
Revisions: 10

format_list_bulletedContents add remove

Tonsillitis refers to inflammation of the palatine tonsils, most commonly due to infection.

Whilst most cases of tonsillitis are mild and fully resolve, significant complications include deep neck space infection and airway compromise.

Tonsillitis is a common presentation in primary care, most common in children and young adults. Recurrent tonsillitis has an incidence in the UK of around 100 per 1000 population a year.

In this article, we shall look at the pathophysiology, clinical features and management of tonsillitis.


The palatine tonsils are located within the oropharynx as part of Waldeyer’s ring (Fig. 1). Waldeyer’s ring is a collection of lymphatic tissue located within the pharynx, forming a ringed arrangement, comprised of the pharyngeal tonsil, tubal tonsils (x2), palatine tonsils (x2), and lingual tonsil.

Tonsillitis is most commonly caused by viral infections (50-80% of cases), including adenovirus, rhinovirus, influenza, and parainfluenza. Bacterial causes account for approximately one third of cases (causative organisms include S. PyogenesS. Aureus, and M. Catarrhalis).

Figure 1 – The four tonsils that comprise Waldeyer’s ring

Clinical Features

Tonsillitis presents with odynophagia or dysphagia, often with associated pyrexia or halitosis. A cough and coryzal symptoms may also be present.

On examination, the tonsils will appear erythematous and swollen (Fig. 2). A purulent exudate may be present (more common in bacterial cases), as well as anterior cervical lymphadenopathy.

Figure 2 – Tonsillitis. The tonsils are erythematous and swollen, with evidence of exudate.

The Centor Criteria

The Centor criteria are often used in primary care to assess for the likelihood of bacterial infection in tonsillitis

Antibiotics should be considered if ≥2 criteria are met:

  • History of pyrexia
  • Tonsillar exudates
  • No cough
  • Tender anterior cervical lymphadenopathy

The Centor criteria however is not suitable for emergency presentations and is rarely used in a hospital setting.

Differential Diagnosis

Important differentials to consider include head and neck malignancy, haematological malignancies, or deep space neck abscess (see below).


Tonsillitis is often a clinical diagnosis; further investigations are only warranted in cases with suspected complications (see below).

Ensuring sufficient analgesia (normally achieved with Difflam spray and regular paracetamol ±NSAIDs) and hydration is the mainstay of treatment. Hospital admission may be required in uncomplicated cases who cannot swallow fluids after initial management.

If the cause is thought to be bacterial, antibiotics should be prescribed (typically penicillin-based, however follow local guidelines)

*Remember that starting amoxicillin in tonsillitis caused by EBV can result in a maculopapular rash developing

Indications for Tonsillectomy

Tonsillectomy can be performed by cold steel excision or diathermy. Typical indications are:

  • ≥7 episodes in the preceding year, or ≥5 episodes in each of preceding 2 years, or ≥3 episodes in each of preceding 3 years
  • Suspected malignancy
  • Presence of sleep apnoea
  • Previous peritonsillar abscess formation

The main complication from tonsillectomy is secondary bleeding (>24hrs post-op) from infection, occurring in around 5% of cases and most at post-operative days 5-9.

This is often treated conservatively, with antibiotic and hydrogen peroxide mouth wash. Fortunately, surgical re-intervention is rarely required


Peritonsillar Abscess

A quinsy is a peritonsillar abscess, a rare complication of bacterial tonsillitis. Patients present with a severe sore throat (worse unilaterally), with associated severe odynophagia. Associated symptoms include stertor and trismus.

On examination (often difficult due to trismus), there will be extensive erythema and soft palate swelling, with the anterior arch being pushed medially and a deviated uvula (Fig. 3).

Patients should be admitted and started on intravenous antibiotics, with regular analgesia and topical analgesic throat sprays. All peritonsillar abscess will require either needle aspiration (following topical local anaesthetic) or an incision and drainage (with further opening via use of Tilley’s forceps)

Figure 3 – A quinsy, causing significant uvula deviation

Deep Space Neck Infection

A rare complication of tonsillitis is the development of a Deep Space Neck Infection. Infection can spread from the tonsils into the surrounding potential spaces between the fascial planes of the neck, either as:

  • Parapharyngeal abscess– forms when infection spreads to the potential space posterolateral to the nasopharynx (most common subtype)
  • Retropharyngeal abscess – infection spreads to the potential space anterior to the prevertebral fascia (commonly seen from necrotising lymph nodes in children)

Pharyngeal abscesses may present in a similar manner to peritonsillar abscesses, however specially will often have associated reduced neck movement, cervical pain, or torticollis (in children).

If a pharyngeal abscess is suspected, a CT scan with IV contrast is the gold-standard investigation, alongside routine bloods and blood cultures.

Any concerns about airway compromise should be addressed as a priority, however most cases will be treated with intravenous antibiotics and surgical drainage.

Key Points

  • Tonsillitis refers to inflammation of the palatine tonsils, most cases of which will resolve with conservative management
  • The Centor criteria is often used in primary care to assess for the likelihood of bacterial infection
  • Peritonsillar abscess and deep space neck infections are rare complications of tonsillitis that should be assessed for in any prolonged, severe, or atypical case