[1][5][6] When caused by the bacterium group A streptococcus, it is classed as streptococcal tonsillitis[11] also referred to as strep throat.

[12] Rarely bacteria such as Neisseria gonorrhoeae, Corynebacterium diphtheriae, or Haemophilus influenzae may be the cause.

[4] Antibiotics probably reduce the number of people experiencing sore throat or headache, but the balance between modest symptom reduction and the potential hazards of antimicrobial resistance must be recognised.

[17] Infectious mononucleosis can cause the tonsils to swell with red spots or white discharge that may extend to the tongue.

[18] This can be accompanied by fever, sore throat, cervical lymph node swelling, and enlargement of the liver and spleen.

[15] Tonsillitis can also stem from infection with bacteria, predominantly Group A β-hemolytic streptococci (GABHS), which causes strep throat.

[21][22][23][24] Anaerobic bacteria have been implicated in tonsillitis, and a possible role in the acute inflammatory process is supported by several clinical and scientific observations.

[1][31] An acute sore throat may be diagnosed as tonsillitis, pharyngitis, or tonsillopharyngitis (also called pharyngotonsillitis), depending upon the clinical findings.

The Centor criteria are also ineffective in diagnosis for tonsillitis in children and in secondary care settings (hospitals).

[15] The diagnosis of GABHS tonsillitis can be confirmed by culture of samples obtained by swabbing the throat and plating them on blood agar medium.

[15] Centor and McIsaac scores are equally ineffective at identifying patients who need antibiotics presenting with pharyngitis at hospitals.

[32] Bacterial culture may need to be performed in cases of a negative rapid streptococcal test.

[15] Nasoendoscopy can be used for those with severe neck pain and inability to swallow any fluids to rule out masked epiglotitis and supraglotitis.

[35] If the tonsillitis is caused by group A streptococcus, then antibiotics are useful, with penicillin or amoxicillin being primary choices.

[1] If penicillin therapy fails, bacterial tonsillitis may respond to treatment effective against beta-lactamase producing bacteria such as clindamycin or amoxicillin-clavulanate.

[37] Aerobic and anaerobic beta lactamase producing bacteria that reside in the tonsillar tissues can "shield" group A streptococcus from penicillins.

[1][5] Paracetamol and nonsteroidal anti-inflammatory drugs (NSAIDs) can be used to treat throat pain in children and adults.

[1][15] Codeine is avoided in children under 12 years of age to treat throat pain or following tonsilectomy.

[50] Recurrent tonsillitis can interfere with vocal function and the ability to perform among people who use their voices professionally.