Swollen tonsils

The tonsils are two lumps of immune tissue at the back of the throat, and they swell when they are fighting infection — so swollen tonsils are usually a sign of tonsillitis or a throat infection. Most cases are viral, part of a cold or other common infection, and come with a sore throat, mild fever and discomfort swallowing, settling within days. A proportion are bacterial — classically streptococcal ('strep throat') — which tends to cause more marked swelling, sometimes with white patches or pus on the tonsils, fever and swollen neck glands, and no cough. Glandular fever (infectious mononucleosis, usually from the Epstein-Barr virus, and sometimes CMV) is another important cause, especially in teenagers and young adults, causing strikingly swollen tonsils, a very sore throat, prominent swollen glands and marked fatigue lasting longer than a typical sore throat. Large tonsils can also be a long-standing feature in some people, occasionally contributing to snoring or disturbed sleep. Warning signs that need urgent attention include severe one-sided swelling with difficulty opening the mouth or swallowing saliva, drooling, or difficulty breathing, which can indicate an abscess or airway problem.

• Viral throat infection — the commonest cause; part of a cold or similar illness.
• Bacterial tonsillitis (strep throat) — more marked swelling, often with white patches, fever and tender neck glands.
• Glandular fever (mononucleosis) — very swollen tonsils, severe sore throat, swollen glands and fatigue; EBV or CMV.
• Chronically enlarged tonsils — a long-standing feature, sometimes causing snoring.
• Peritonsillar abscess — severe one-sided swelling; a warning sign needing urgent care.

Most sore throats with swollen tonsils are viral and need no tests, settling with simple care. When a bacterial (strep) cause is suspected, a rapid throat swab or a scoring of the features guides whether antibiotics are needed. If glandular fever is suspected — a young person with very swollen tonsils, marked fatigue and swollen glands — a monospot test, EBV serology, a full blood count (which may show a rise in lymphocytes) and liver markers help confirm it. CRP and white cell count reflect how much infection is present. Mediora.AI can show a mono-like blood pattern and EBV markers alongside inflammatory markers so the picture behind swollen tonsils is visible; the diagnosis and any treatment belong with your doctor.