What Is Tonsillitis? Causes, Symptoms and Treatment Explained

Have You Ever Wondered Why Your Tonsils Become Swollen When You Have a Sore Throat?

Most of us have experienced a sore throat at some point. It often begins as a scratchy irritation before becoming painful to swallow, leaving us reaching for a hot drink or lozenges in the hope that it will soon pass. While many sore throats are caused by mild viral infections and settle on their own, others occur because the tonsils themselves have become inflamed; a condition known as tonsillitis. Acute sore throat, including tonsillitis, is most commonly caused by a viral infection and usually improves within a week without antibiotics.

What Exactly Are the Tonsils?

Those two small lumps at the back of your throat are far more important than they might appear. The palatine tonsils are made up of specialised lymphoid tissue and form part of Waldeyer's ring: a ring of immune tissue that also includes the adenoids (pharyngeal tonsil), lingual tonsils and tubal tonsils. Together, these structures help monitor the bacteria, viruses and other microorganisms entering through your mouth and nose, allowing your immune system to respond quickly when harmful pathogens are detected.

Rather than acting as a physical barrier, the tonsils function like an early warning system. Their surface contains deep folds, known as tonsillar crypts, which increase the surface area exposed to inhaled and swallowed microorganisms. Within these crypts are specialised immune cells, including B lymphocytes, T lymphocytes and antigen-presenting cells, that work together to recognise potential pathogens and coordinate an immune response before an infection has the opportunity to spread further into the body.

So Why Do the Tonsils Become Swollen?

When bacteria or viruses invade the tissues of the throat, the immune system immediately begins responding. Chemical messengers released by immune cells trigger inflammation, causing nearby blood vessels to widen and become more permeable. This allows white blood cells, antibodies and other immune proteins to leave the bloodstream and enter the infected tissue, where they help identify and destroy the invading microorganisms.

Although this inflammatory response is essential for fighting infection, it is also responsible for the symptoms we experience. Increased blood flow causes the tonsils to become red and warm, fluid leaking into the tissues leads to swelling, while inflammatory chemicals stimulate pain receptors, making swallowing uncomfortable or even painful. In many people, nearby lymph nodes in the neck also become enlarged as they help filter pathogens and support the immune response.

Viral or Bacterial?

One of the biggest misconceptions about tonsillitis is that it always requires antibiotics. Most cases are caused by viruses, meaning antibiotics won't speed up recovery or improve symptoms. Instead, treatment usually focuses on getting plenty of rest, staying hydrated and using simple pain relief, such as paracetamol or ibuprofen if appropriate, while the body's immune system clears the infection (NICE, 2018).

Some cases, however, are caused by bacteria, most commonly Group A Streptococcus (Streptococcus pyogenes). As the symptoms of viral and bacterial tonsillitis can be very similar, healthcare professionals don't rely on appearance alone. Instead, they consider the patient's symptoms, clinical examination and where appropriate, use tools such as the FeverPAIN or Centor score to estimate how likely a bacterial infection is and whether antibiotics are likely to be beneficial (NICE, 2018).

This approach helps ensure antibiotics are prescribed only when they're genuinely needed. Not only does this reduce unnecessary side effects for patients, but it also plays an important role in slowing the development of antimicrobial resistance which is one of the biggest challenges facing healthcare today.

References

• Abbas, A.K., Lichtman, A.H. and Pillai, S. (2023) Basic Immunology: Functions and Disorders of the Immune System. 7th edn. Philadelphia, PA: Elsevier.
• Mescher, A.L. (2024) Junqueira's Basic Histology: Text and Atlas. 17th edn. New York: McGraw Hill.
• National Institute for Health and Care Excellence (NICE) (2018) Sore throat (acute): antimicrobial prescribing. NICE Guideline NG84. Available at: https://www.nice.org.uk/guidance/ng84