What is tonsillitis?

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Last updated: November 26, 2025View editorial policy

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What is Tonsillitis

Tonsillitis is inflammation of the palatine tonsils caused by viral or bacterial infection of the tonsillar tissue, presenting as sore throat with visible inflammation of the tonsils and pharynx. 1, 2

Definition and Pathophysiology

  • Tonsillitis is defined as sore throat caused by viral or bacterial infection of the pharynx, palatine tonsils, or both, which may or may not be culture positive for group A streptococcus. 1

  • The condition encompasses terms including strep throat, acute tonsillitis, pharyngitis, adenotonsillitis, and tonsillopharyngitis. 1

  • Tonsillitis represents an inflammatory process of the tonsillar tissues that is usually infectious in nature, affecting the lymphoid tissue of the palatine tonsils. 3

Etiology and Epidemiology

  • Viral infections account for 70% to 95% of tonsillitis cases, making them the predominant cause. 4

  • Bacterial tonsillitis caused by group A beta-hemolytic streptococcus (Streptococcus pyogenes) accounts for 5% to 15% of cases in adults and 15% to 30% of cases in children aged 5 to 15 years. 4

  • The condition predominantly affects school-aged children but can occur in patients of any age. 3

  • Tonsillitis makes up approximately 0.4% of outpatient visits in the United States. 4

Clinical Presentation

Viral Tonsillitis

  • Typically lacks high fever, tonsillar exudate, and cervical lymphadenopathy. 5

  • Presents with sore throat and difficulty swallowing, with visible inflammation of the tonsils on examination. 6

Bacterial Tonsillitis (Group A Streptococcus)

  • Characterized by sudden onset of sore throat, fever >38°C (100.9°F), tonsillar exudates, tender anterior cervical lymphadenopathy, and absence of cough. 5, 7

  • Physical examination reveals erythema of the uvula, pharynx, or tonsils, often with edema and potentially exudate. 1

Diagnostic Approach

  • Testing before treating is essential: use rapid antigen detection testing (RADT) and/or throat culture for group A Streptococcus before initiating antibiotic therapy. 7

  • At least 10 colonies of group A beta-hemolytic streptococci should be present on the culture plate for a positive diagnosis. 1

  • Throat specimens should be obtained from the posterior pharynx and uvula using a throat swab prior to initiating anti-infective therapy. 1

Impact on Quality of Life

  • Recurrent throat infections and tonsillitis can substantially affect child health status and quality of life. 1

  • Children with tonsillar disease show significantly lower scores on quality of life subscales including general health, physical functioning, behavior, bodily pain, and caregiver impact compared with healthy children. 1

  • The condition leads to increased healthcare usage, missed school days, and spread of infection within families. 1

Complications

  • Differentiating group A beta-hemolytic streptococcus from other causes is critical due to risk of progression to systemic complications including peritonsillar abscess, parapharyngeal abscess, acute glomerulonephritis, rheumatic fever, and scarlet fever. 4, 2

  • Life-threatening complications can develop, highlighting the need for appropriate recognition and management. 2

Treatment Principles

Viral Tonsillitis

  • Treatment is supportive with analgesia (NSAIDs or acetaminophen) and adequate hydration. 6, 5

Bacterial Tonsillitis

  • Penicillin V for 10 days is the gold standard treatment for confirmed group A streptococcal tonsillitis, with amoxicillin as an acceptable alternative. 7

  • The full 10-day course is mandatory to maximize bacterial eradication and prevent rheumatic fever and glomerulonephritis, even though shorter courses may resolve symptoms. 7

  • For penicillin-allergic patients with non-anaphylactic allergy, first-generation cephalosporins are recommended; for anaphylactic allergy, clindamycin, azithromycin, or clarithromycin should be used. 7

Recurrent Tonsillitis

  • Recurrent tonsillitis is defined by frequency: at least 7 episodes in the past year, at least 5 episodes per year for 2 years, or at least 3 episodes per year for 3 years. 1

  • Each documented episode must include temperature >38.3°C (101°F), cervical adenopathy, tonsillar exudate, or positive test for group A streptococcus. 1

  • Watchful waiting is strongly recommended if episodes are fewer than these thresholds before considering tonsillectomy. 4

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Acute tonsillitis and its complications: an overview.

Journal of the Royal Naval Medical Service, 2015

Research

Acute tonsillitis.

Infectious disorders drug targets, 2012

Research

Tonsillitis and Tonsilloliths: Diagnosis and Management.

American family physician, 2023

Guideline

Differentiating Viral from Bacterial Tonsillitis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

Research

Tonsillitis.

Primary care, 2025

Guideline

Treatment Options for Tonsillitis

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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