Question

What is allergy? Explain with an example.

Hint:

IgE antibodies + mast cells + histamine release.

Answer 1

Step 1: Define allergy:
Allergy is an exaggerated (hypersensitive) response of the immune system to certain harmless environmental antigens, called allergens.

Step 2: Explain the underlying mechanism:
On first exposure, the allergen triggers the production of IgE antibodies, which bind to mast cells; on re-exposure, the allergen cross-links these bound IgE antibodies, causing mast cells to release chemicals like histamine and serotonin, which produce the visible allergic symptoms.

Step 3: Give an example:
Exposure to dust or pollen commonly triggers symptoms such as sneezing, watery eyes, and a runny nose (a condition often called hay fever) in susceptible individuals.

Final Answer:
Allergy is an IgE-mediated hypersensitive immune reaction to allergens like dust or pollen, producing symptoms such as sneezing and watery eyes.