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 1
Allergy
An allergy is an overreaction of the immune system to a normally harmless substance, causing symptoms ranging from mild to severe.
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.
Exam highlight
Key diagram
Keywords worth remembering
Trending
allergyicse class 7
Most searched
ICSE class 7 allergy
Quick revision
Study resources
Notes & downloads
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.