Chapter 7 · ICSE Class 7 Biology (Selina Concise)

Allergy

Learn what an allergy is, common allergens, and how the body's immune system reacts to them.

🤧 Chapter 7

How the body reacts to an allergen, causing allergy symptoms A flow showing that an allergen such as pollen or dust enters the body, the immune system overreacts to it, and this causes symptoms like sneezing or itching Allergen pollen, dust → Immune System overreacts → Symptoms sneezing, itch
7.1

What is an Allergy

An allergy is an overreaction of the immune system to a normally harmless substance (allergen), causing symptoms like sneezing, itching, or rashes.

1

What is an allergen?

A substance that triggers an allergic reaction in a sensitive person

2

Why do allergic reactions happen to substances that aren't actually harmful?

Because the immune system mistakenly identifies the harmless substance as a threat and overreacts to it

7.2

Common Allergens and Symptoms

Common allergens include pollen, dust, certain foods, and pet dander. Symptoms can range from mild (sneezing, itching) to severe (difficulty breathing).

1

Name a common allergen.

Pollen, dust mites, certain foods (like peanuts), or pet dander

2

Name one symptom of an allergic reaction.

Sneezing, itching, rashes, or swelling

Practice

Exercises

1. What is an allergy?

2. What is an allergen?

3. Name a common allergen.

4. Name one common symptom of an allergic reaction.

5. Why might someone need to avoid certain foods due to allergies?

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