Question

Histamine is responsible for various physiological effects. Which of the following statements are correct?

• [(I)] Histamine is a potent vasodilator.

• [(II)] Histamine lowers blood pressure by constricting blood vessels.

• [(III)] Histamine is responsible for nasal congestion associated with common cold and allergies.

• A. I and II only
• B. II and III only
• C. I and III only
• D. I, II and III

Hint:

Antihistamines work by blocking the action of histamine and are commonly used to treat allergies, hay fever and cold-related symptoms.

Answer 1

The Correct Option is C

Step 1: Know what histamine does.
Histamine is released in the body during allergies and inflammation. It affects blood vessels, the nose and the stomach.

Step 2: Check Statement (I).
Histamine widens blood vessels, so it is a strong vasodilator. Statement (I) is correct.

Step 3: Check Statement (II).
Statement (II) says histamine lowers blood pressure by narrowing vessels. This is wrong, because histamine widens vessels, it does not narrow them. So Statement (II) is incorrect.

Step 4: Check Statement (III).
Histamine causes swelling and a blocked nose during colds and allergies. So Statement (III) is correct.

Step 5: Collect the correct ones.
Correct statements are (I) and (III). Statement (II) is the only wrong one.

Step 6: Match with the options.
The set that holds (I) and (III) only is the right choice.

Step 7: State the final answer.
The correct combination is:
\[ \boxed{\text{I and III only}} \]