Question

What is Allergy? Explain with examples.

Hint:

Allergen → IgE antibody → mast cell → histamine release → allergy symptoms.

Answer 1

Step 1: Definition:
Allergy is an exaggerated (hypersensitive) response of the immune system to certain otherwise harmless foreign substances present in the environment, called allergens.

Step 2: Mechanism:
On exposure to an allergen, the body produces IgE antibodies, which bind to mast cells. On re-exposure to the same allergen, mast cells release histamine and other chemicals, causing symptoms like sneezing, watery eyes, breathlessness, or skin rashes.

Step 3: Examples:
Common allergens include dust mites and pollen (causing allergic rhinitis/hay fever), certain foods like peanuts and seafood, and drugs like penicillin, which can trigger reactions ranging from mild rashes to severe, life-threatening anaphylaxis.

Final Answer:
Allergy is a hypersensitive immune reaction, mediated mainly by IgE and histamine, triggered by allergens such as dust, pollen or certain foods.