Worksheet Solutions: Allergy | Biology Class 7 ICSE PDF Download

Part A: Multiple Choice Questions (MCQs)

Q1. Which scientist first introduced the term “allergy”?
a) Alexander Fleming
b) Louis Pasteur
c) Clemens von Pirquet
d) Robert Koch

Answer: (c) Clemens von Pirquet
Explanation: In 1906, Clemens von Pirquet observed that some people showed hypersensitivity to harmless substances and coined the term “allergy.”

Q2. Which chemical released during allergic reactions is responsible for symptoms like rashes and swelling?
a) Insulin
b) Histamine
c) Hemoglobin
d) Bile

Answer: (b) Histamine
Explanation: Histamine is released when allergens trigger immune cells. It causes inflammation, itching, and other allergy symptoms.

Q3. Which of the following is a seasonal allergy trigger?
a) Milk
b) Penicillin
c) Pollen
d) Dust mites

Answer: (c) Pollen
Explanation: Pollen from flowers in spring and summer causes sneezing, runny nose, and watery eyes, which are typical seasonal allergies.

Q4. Which of these is the most serious allergic reaction that can be life-threatening?
a) Hay fever
b) Hives
c) Anaphylaxis
d) Asthma

Answer: (c) Anaphylaxis
Explanation: Anaphylaxis is a severe reaction leading to low blood pressure and difficulty in breathing. Immediate medical care is required.

Q5. Which test involves pricking the skin with allergen drops to check for reactions?
a) Blood sugar test
b) Skin prick test
c) ECG test
d) Biopsy

Answer: (b) Skin prick test
Explanation: In the skin prick test, small drops of allergens are placed on the skin, which is pricked. Redness or swelling indicates an allergy.

Part B: Short Answer Questions

Q6. What is an allergy?
Answer:
An allergy is an overreaction of the immune system to harmless substances like dust, pollen, or certain foods. These substances are called allergens. The immune system produces histamine, which causes symptoms like sneezing, rashes, or breathing problems.

Q7. Name any three common allergens and the way they enter the body.
Answer:

1. Dust and pollen – enter through the nose while breathing.

2. Certain foods – like milk, peanuts, and seafood, enter through the mouth.

3. Insect stings or latex – enter through the skin.

Q8. List two symptoms of food allergy and two symptoms of airborne allergy.
Answer:

• Food allergy symptoms: vomiting, itchy skin, swelling.

• Airborne allergy symptoms: sneezing, watery eyes, coughing.

Q9. What is the difference between seasonal allergy and dust allergy?
Answer:

• Seasonal allergy happens mainly during flowering seasons due to pollen. It causes sneezing, itchy eyes, and runny nose.

• Dust allergy occurs when dust particles enter the airways, often triggering asthma and breathing difficulty.

Q10. How can people prevent allergic reactions?
Answer:

• By identifying and avoiding the allergen (e.g., avoiding peanuts if allergic).

• Keeping homes dust-free.

• Using medicines or anti-allergy shots prescribed by doctors.

• Consulting specialists in case of severe allergies.

Part C: Long Answer Questions (with Stepwise Solutions)

Q11. Explain the role of histamine in allergic reactions.

Answer:
Step 1: When allergens like dust or pollen enter the body, the immune system identifies them as harmful (even though they are not).
Step 2: The immune system produces immunoglobulin proteins that attach to white blood cells.
Step 3: These cells then release a chemical called histamine.
Step 4: Histamine causes:

• Inflammation of tissues.

• Redness and rashes on skin.

• Swelling of airways leading to asthma.

• Sneezing, watery eyes, and itching.
  Conclusion: Histamine is the main chemical responsible for allergy symptoms.

Q12. Describe the process of allergy testing.

Answer:
Step 1: Skin Prick Test – A drop of allergen solution is placed on the skin. The skin is pricked lightly.

• If allergic, redness or swelling appears within 30 minutes.

• A saline drop is used as control to compare reactions.

Step 2: Blood Test – A small blood sample is collected.

• The laboratory checks for antibodies against specific allergens.

• This test is safe for all ages, during pregnancy, and when skin conditions make the prick test unsuitable.

Conclusion: Allergy testing helps confirm which substances trigger allergic reactions, making it easier to manage and prevent them.

Q13. What is anaphylaxis? Explain its symptoms and treatment.

Answer:
Step 1: Definition – Anaphylaxis is a sudden, severe allergic reaction that affects the whole body.
Step 2: Causes – Triggered by insect stings, medicines (like penicillin), or certain foods like nuts and seafood.
Step 3: Symptoms –

• Skin redness and rashes.

• Swelling of face, lips, or throat.

• Severe breathing difficulty due to bronchial narrowing.

• Drop in blood pressure.
  Step 4: Treatment –

• Immediate medical help is needed.

• Patients are usually given injections of adrenaline (epinephrine) to open airways and stabilize blood pressure.

• Further hospital care may be required.