Q1
What is an allergy?
AAn immune overreaction to a harmless substance
BA type of infection
CA type of injury
DNothing specific
ICSEClass 7 (ICSE)ScienceCh 21 · Topic 2
Practice and Revision - Allergy
Let us practise and revise what we learned about allergy. An allergy is an overreaction of the immune system to a normally harmless substanc
Core concept
Common allergens (substances causing allergies) include pollen, dust, certain foods, and pet dander, triggering an immune response in sensitive people.
How it works
Allergic reactions can cause symptoms like sneezing, itching, rashes, or in severe cases, difficulty breathing (anaphylaxis).
Why it matters
The immune system mistakenly identifies the allergen as harmful, releasing chemicals like histamine that cause allergy symptoms.
Key detail
Managing allergies involves avoiding known allergens, taking medication when needed, and seeking medical help for severe reactions.
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Quick notes
• An allergy is an immune overreaction to a harmless substance.
• Common allergens: pollen, dust, foods, pet dander.
• Allergic reactions cause sneezing, itching, rashes.
• Severe reactions can cause difficulty breathing (anaphylaxis).
• The immune system mistakes the allergen as harmful.
• It releases histamine, causing symptoms.
• Managing allergies means avoiding allergens.
• Medication and medical help manage severe reactions.