Read the following statements:
Statement I: Excessive release of chemicals like histamine by mast cells in humans can cause allergic reactions.
Statement II: When allergens enter the human body, they trigger the activation of mast cells.
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Both statement I and statement II are correct.
Allergy is an exaggerated response of the immune system to some harmless substances in the environment, called allergens. Examples are mites in dust, pollen and animal dander. The body makes IgE antibodies against them. The mast cells then release chemicals such as histamine and serotonin, which cause the symptoms.
Statement I: Excessive release of chemicals like histamine by mast cells in humans can cause allergic reactions. — True. Allergy is due to the release of histamine and serotonin from mast cells. Sneezing, watery eyes, running nose and difficulty in breathing follow.
Statement II: When allergens enter the human body, they trigger the activation of mast cells. — True. The allergen sets off the immune response, and the mast cells respond by releasing their chemicals. That is why anti-histamine drugs reduce the symptoms.
NCERT Extract:
Allergies – “The exaggerated response of the immune system to certain antigens present in the environment is called allergy. The substances to which such an immune response is produced are called allergens. The antibodies produced to these are of IgE type. … Allergy is due to the release of chemicals like histamine and serotonin from the mast cells. … The use of drugs like anti-histamine, adrenalin and steroids quickly reduce the symptoms of allergy.”