Acute tonsillitis is an acute infection of the palatine tonsils resulting in a sore throat. It can be of viral or bacterial cause. Viral causes are more common. Most cases are self-limiting and don’t require antibiotics. Children aged 5-15 years are more commonly affected. However, it is important to remember that the majority of sore throats are not caused by tonsillitis.


  • Incidence: 500.00 cases per 100,000 person-years
  • Peak incidence: 6-15 years
  • Sex ratio: 1:1
Condition Relative
Viral upper respiratory tract infections60.00
Acute tonsillitis1
Peritonsillar abscess (quinsy)0.06
Acute epiglottitis0.004
<1 1-5 6+ 16+ 30+ 40+ 50+ 60+ 70+ 80+


  • Viral
    • Tonsillitis is usually viral.
    • Rhinovirus, coronavirus and parainfluenza virus (ordered from most to least common) account for 25% of all sore throats
    • Adenovirus (4%)
    • Influenza virus type A and B (4%)
    • Herpes simplex virus (2%)
    • Epstein-Barr virus (glandular fever; 1%).
  • Bacterial
    • Group A ß–haemolytic streptococci (20% in children; 10% in adults)
    • Group C ß–haemolytic streptococci (5%)
    • Rarer bacterial causes: Mycoplasma pneumonia and Neisseria gonorrhoea.


Acute tonsillitis is the inflammatory infection of the palatine tonsils:
  • Micro-organisms which successfully penetrate the tonsillar epithelium are phagocytosed by macrophages.
  • Macrophages then process and present them to B and T cells within the tonsils, thus stimulating cellular and humoral immune responses.
  • Inflammatory cytokines (e.g. phospholipase A2) are produced.
    • Such local inflammatory pathways destroy the virus or bacteria, cause pyrexia and result in oropharyngeal swelling, pain and erythema.

Clinical features

Patients typically present with a combination of an acute onset of:
  • Sore throat (99%)
  • Fever >38ºC (82%)
  • Dysphagia (66%)
  • Nasal congestion, headache, earache, cough (47%)
    • These 4 symptoms may be present if viral aetiology.
    • If no cough is present, this is more likely bacterial cause.

Examination of the pharynx may reveal:
  • Severely inflamed tonsils (87%)
  • Painfully enlarged anterior cervical lymph nodes (49%)
  • Purulent tonsils (41%)
    • Pus on the tonsils is suggestive of bacterial cause.

Do not examine if epiglottitis suspected.
  • Additional features suggestive of epiglottitis:
    • A young child
    • A muffled voice
    • Excessive drooling and pooling of saliva.
  • Call for an anaesthetist and an ENT surgeon.


Acute tonsillitis is usually a clinical diagnosis.
  • Investigations are only used if confirmation of group A streptococcal (GAS) infection is required (e.g. in patients on immunosuppression, very old or young, with severe symptoms).
    • In these patients, the NICE 2018 Clinical Knowledge Summary suggests performing a rapid antigen test for GAS.
    • If this antigen test is negative, a throat culture should be performed.

In all other patients, clinical examination in combination with a clinical prediction score (FeverPAIN or Centor - see 'Management' section) should be used to establish the likelihood of GAS infection.
  • This is important, as GAS aetiology requires antibiotic treatment.

Differential diagnosis

  • Viral upper respiratory tract infection
    • Similarities: sore throat, fever.
    • Differences: coryza, nasal obstruction, facial pain, earache.
  • Primary herpes labialis (oral herpes)
    • Similarities: sore throat, fever cervical lymphadenopathy.
    • Differences: mouth pain, burning or tingling, visible vesicles or crusted ulcer.
  • Peritonsillar abscess (quinsy)
    • Can be a complication of tonsillitis.
    • Similarities: sore throat, high fever, dysphagia.
    • Differences: trismus (lockjaw), muffled voice, uvular deviation, unilateral enlarged and displaced tonsil.
  • Infectious mononucleosis
    • Similarities: sore throat, fever, lymphadenopathy.
    • Differences: does not resolve after 1 week, splenomegaly, hepatomegaly, persistent fatigue, weight loss.
  • Epiglottitis
    • An airway emergency. Can be life-threatening due to airway obstruction.
    • Now rare since Haemophilus influenza type B is vaccinated against in routine childhood immunisations.
    • Similarities: sore throat, high fever.
    • Differences: muffled voice, excessive drooling (in children), possible stridor and breathing difficulty.
  • Retropharyngeal abscess
    • Collection of pus in the space between the pre-vertebral fascia and the neck constrictor muscles.
    • Can be life-threatening if not identified early.
    • Similarities: sore throat, high fever, dysphagia.
    • Differences: trismus (lockjaw), visible neck swelling, torticollis.
  • Gonococcal pharyngitis
    • Similarities: sore throat, high fever, dysphagia.
    • Differences: adolescent and adult patients with history of oral sex (sexually transmitted).
  • Primary HIV infection
    • Similarities: sore throat, high fever, lymphadenopathy.
    • Differences: more generalised lymphadenopathy, weight loss, fatigue, malaise, risk factors for HIV.


Reassurance and symptomatic relief advise should be offered to all patients (NICE 2018 guidelines).
  • Reassure – symptoms can last for around 1 week, but most people get better within this time without treatment.
  • Paracetamol or ibuprofen – for pain or fever.
  • Fluids – adequate intake maintained.

Other treatment
  • antibiotics are not routinely indicated, but may be indicated if certain criteria are met as below
    • if antibiotics are indicated then either phenoxymethylpenicillin or erythromycin (if the patient is penicillin allergic) should be given. Either a 7 or 10 day course should be given
  • there is some evidence that a single dose of oral corticosteroid may reduce the severity and duration of pain, although this has not yet been incorporated into UK guidelines

NICE indications for antibiotics
  • features of marked systemic upset secondary to the acute sore throat
  • unilateral peritonsillitis
  • a history of rheumatic fever
  • an increased risk from acute infection (such as a child with diabetes mellitus or immunodeficiency)
  • patients with acute sore throat/acute pharyngitis/acute tonsillitis when 3 or more Centor criteria are present

Scoring systems

The Centor criteria are: score 1 point for each (maximum score of 4)

Centor scoreLikelihood of isolating Streptococci
0 or 1 or 23 to 17%
3 or 432 to 56%

The FeverPAIN criteria are: score 1 point for each (maximum score of 5)
  • Fever over 38°C.
  • Purulence (pharyngeal/tonsillar exudate).
  • Attend rapidly (3 days or less)
  • Severely Inflamed tonsils
  • No cough or coryza

FeverPAIN scoreLikelihood of isolating Streptococci
0 or 113 to 18%
2 or 334% to 40%
4 or 562% to 65%

Special patient groups:
  • If on DMARDs or carbimazole, check FBC urgently.
  • If immunosuppressed (eg leukaemia, HIV/AIDS), seek urgent specialist advice.


Complications of acute tonsillitis are rare.

Potential complications include:
  • Acute otitis media
    • Common, benign and self-limiting.
    • Antibiotics reduce the risk.
  • Peritonsillar abscess (quinsy) or neck abscess
    • Usually in the first 2 months after acute tonsillitis episode.
    • Presents with spiking fever, neck pain and dysphagia.
    • Antibiotics reduce the risk. Drainage required.
  • Acute sinusitis
    • In 0.4% of untreated patients.
    • Antibiotics reduce the risk.
These very rare complications usually only occur if an underlying bacterial infection is untreated, and include:
  • Scarlet fever
    • Presents as a blanching erythematous papular rash, a strawberry tongue and circumoral pallor.
  • Acute rheumatic fever
    • Extremely rare (<1:100,000).
    • Causes widespread inflammation throughout the body.
    • Presents with arthritis, subcutaneous nodules, erythema marginatum, chorea and carditis.
    • Antibiotics reduce the risk.
  • Acute post-streptococcal glomerulonephritis:
    • Exceedingly rare.
    • Presents with haematuria, oedema, vomiting and anorexia.
  • Streptococcal toxic shock syndrome:
    • Very rare but life-threatening.
    • Presents with progressive multiple organ failure and shock.
    • Due to exaggerated inflammatory response to streptococcal antigens.