Common Misconceptions

Misconception: "White blood cells eat all pathogens the same way."

Reality: Only phagocytes (neutrophils and macrophages) engulf pathogens by phagocytosis. Other white blood cells work differently — B lymphocytes produce antibodies, T lymphocytes kill infected cells directly. Even among phagocytes, neutrophils and macrophages differ in size, lifespan, and function. Saying "white blood cells engulf pathogens" is only partly correct and would score partial marks on an exam.

Misconception: "Mucus kills bacteria."

Reality: Mucus itself does not kill bacteria — it physically traps them. The killing is done by lysozyme and other antimicrobial chemicals dissolved within the mucus. Mucus is sticky because of glycoproteins, and this stickiness is what captures pathogens. The cilia then sweep the mucus away before pathogens can escape and cause infection.

Misconception: "Inflammation is harmful and the body is trying to stop it."

Reality: Inflammation is a beneficial protective response — redness, heat, swelling, and pain are signs that the immune system is working correctly. The redness and heat result from increased blood flow delivering more white blood cells. Swelling is caused by fluid leaving capillaries to bring immune cells into infected tissue. Without inflammation, infections would spread unchecked. Problems arise only when inflammation is excessive or chronic.

Misconception: "The stomach acid kills everything you swallow."

Reality: Stomach acid (pH 1-2) kills most pathogens but not all. Some bacteria have evolved adaptations to survive stomach acid — for example, Helicobacter pylori produces urease to neutralise acid locally, allowing it to survive and cause stomach ulcers. Some spore-forming bacteria can survive as dormant spores that are acid-resistant. Food should still be handled hygienically even though some pathogens will be killed by stomach acid.