Tonsillitis — Causes, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Tonsillitis is inflammation of the palatine tonsils — two oval-shaped lymphoid tissue masses at the back of the throat — most commonly caused by viral or bacterial infection. It is one of the most frequent reasons for medical consultation and antibiotic prescription in children and young adults. Most cases of tonsillitis are viral (Adenovirus, EBV, Rhinovirus), self-limiting, and resolve without antibiotics. Group A Streptococcus (GAS — Streptococcus pyogenes) is the most important bacterial cause, accounting for 15-30% of pharyngitis in adults and up to 40% in children, and requiring antibiotic treatment to prevent complications. Tonsillitis is classified as acute (single episode), recurrent (7+ episodes per year, or 5 per year for 2 years), and chronic. The Centor and McIsaac clinical scoring systems allow evidence-based decisions about antibiotic prescribing in tonsillitis, reserving antibiotics for patients with bacterial indicators while avoiding unnecessary prescribing in the majority of cases which are viral and self-limiting.

Viral causes (most common — 70-80%): Adenovirus (most frequent), Epstein-Barr virus (EBV — causing infectious mononucleosis/glandular fever with exudative tonsillitis and profound fatigue), Rhinovirus, Coronavirus, Influenza, and Parainfluenza. Bacterial causes: Group A Streptococcus (GAS/Streptococcus pyogenes) — most important due to risk of rheumatic fever and peritonsillar abscess; Fusobacterium necrophorum (young adults — risk of Lemierre's syndrome); Group C and G Streptococci; Mycoplasma pneumoniae (atypical). Risk factors include age 5-15 years (school-age children most affected), close contact in school or daycare settings, immunosuppression, smoking, and winter months (coinciding with respiratory virus season). Kissing spreads EBV — 'kissing disease'. Fusobacterium necrophorum — commonly underappreciated as a pathogen — is an important bacterial cause of exudative tonsillitis in young adults, capable of causing the serious and potentially fatal Lemierre syndrome through internal jugular vein thrombophlebitis.

Sore throat — typically severe, aggravated by swallowing (odynophagia), dysphagia (difficulty swallowing), fever (often high, above 38.5°C in bacterial cases), halitosis (bad breath), muffled or 'hot potato' voice (suggesting peritonsillar abscess if extreme), headache, malaise, and abdominal pain in children. On examination: erythematous (red), enlarged tonsils — with or without white/yellow exudates (purulent tonsillitis), tender anterior cervical lymph nodes (lymphadenopathy). Centor/McIsaac criteria score bacterial probability: tonsillar exudate (+1), tender anterior cervical nodes (+1), absence of cough (+1), fever (+1), age under 15 (+1). Score 3-5 suggests bacterial aetiology — consider throat swab and antibiotic treatment. Glandular fever (EBV): marked splenomegaly, petechiae on soft palate, bilateral lymphadenopathy, and profound fatigue lasting weeks — do not give amoxicillin (causes characteristic maculopapular rash in 90% of EBV cases).

Clinical diagnosis using Centor/McIsaac criteria guides antibiotic decisions in primary care. Rapid antigen detection test (RADT — Strep A test): sensitive (80-90%) and specific (95-99%) for GAS pharyngitis — allows point-of-care diagnosis. Throat swab and culture: gold standard but results take 24-48 hours — used when RADT is negative but clinical suspicion remains high, or for epidemiological surveillance. Blood tests for suspected glandular fever: FBC (atypical lymphocytosis, lymphocytosis), Monospot test (heterophile antibodies — positive in 80% of EBV), EBV IgM serology for monospot-negative cases. Ultrasound neck and CT neck with contrast for suspected peritonsillar or parapharyngeal abscess. Lateral neck X-ray for suspected retropharyngeal abscess. Throat swab culture is recommended in recurrent tonsillitis before tonsillectomy to identify carrier organisms.

Viral tonsillitis: supportive care — adequate hydration, paracetamol or ibuprofen for pain and fever, soluble or lozenges for throat, honey and lemon. Antibiotics are not indicated. Bacterial (GAS) tonsillitis: Phenoxymethylpenicillin (penicillin V) 500mg four times daily for 10 days — first-line; or Amoxicillin 500mg three times daily for 5-7 days. Avoid amoxicillin if EBV is suspected. Azithromycin or clarithromycin for penicillin allergy. Complete the full course to prevent rheumatic fever. Analgesia: regular paracetamol + ibuprofen for severe pain; soluble aspirin gargle in adults; anaesthetic throat spray (benzocaine/lidocaine). IV fluids for severe odynophagia causing dehydration. Peritonsillar abscess (quinsy): drainage by needle aspiration or incision plus IV antibiotics (benzylpenicillin + metronidazole); tonsillectomy at the interval. Tonsillectomy: indicated for recurrent tonsillitis (NHS criteria: 7+ episodes in 1 year, 5+ in 2 consecutive years, or 3+ in 3 consecutive years, with significant impact on quality of life). Also indicated for obstructive sleep apnoea, peritonsillar abscess, and suspected lymphoma.

Most acute tonsillitis resolves without complication, but several serious local and systemic complications can occur. Peritonsillar abscess (quinsy) is the most common complication — pus collects between the tonsil and surrounding tissue causing worsening unilateral pain, muffled voice, trismus, uvular deviation, and risk of airway compromise; requires surgical drainage and IV antibiotics. Parapharyngeal and retropharyngeal space infections represent more serious spread of infection into deep neck spaces — risking airway obstruction and jugular vein thrombosis. Lemierre's syndrome — predominantly caused by Fusobacterium necrophorum — causes septic thrombophlebitis of the internal jugular vein with septic pulmonary emboli; mortality reaches 15% even with treatment, and most commonly affects young adults following tonsillopharyngeal infection. Rheumatic fever complicates untreated Group A Streptococcal tonsillitis in 0.3-3% of cases — causing carditis, migratory polyarthritis, and Sydenham's chorea; GAS carditis can cause permanent mitral and aortic valve disease. Post-streptococcal glomerulonephritis from immune complex deposition causes haematuria, proteinuria, and hypertension 1-3 weeks after GAS pharyngitis. Tonsillar hypertrophy in children can cause obstructive sleep apnoea, cor pulmonale, and failure to thrive if unrecognised and untreated.

Frequent handwashing with soap and water, particularly before eating and after contact with ill individuals. Avoid sharing food, utensils, or drinks. Cover mouth and nose when coughing or sneezing. Children with bacterial tonsillitis should stay home from school for at least 24 hours after starting antibiotics and until fever-free. There is no vaccine against Group A Streptococcus or adenovirus. For recurrent tonsillitis, ENT specialist assessment to determine tonsillectomy candidacy should be sought when episodes meet surgical thresholds. Maintain adequate hydration and rest to support immune recovery. Quit smoking — smoking impairs tonsillar and upper respiratory tract immunity and increases infection frequency and severity.

Seek emergency care immediately for: inability to swallow saliva or drooling (suggests peritonsillar abscess or epiglottitis), stridor (noisy breathing), severe breathing difficulty, neck stiffness and swelling (parapharyngeal or retropharyngeal abscess, Lemierre's syndrome), trismus (inability to open the mouth), or severe systemic toxicity. See a doctor promptly for sore throat with very high fever, marked tonsillar swelling with exudate, inability to eat or drink, symptoms persisting beyond 7 days, or Centor score of 3 or above warranting antibiotic consideration. Children with suspected glandular fever should avoid contact sports for 4 weeks due to splenomegaly and splenic rupture risk. Return to your GP or attend A&E without delay if throat pain is markedly worsening after day 3-4 of antibiotic therapy, if you develop severe difficulty opening your mouth or swallowing your own saliva, or if you develop a unilateral throat swelling — these suggest peritonsillar abscess formation requiring urgent surgical drainage.