Histamine is a potent vasodilator. Hence, Statement 2 is correct. It has various functions . It contracts the smooth muscles in the bronchi and gut and relaxes other muscles, such as those in the walls of fine blood vessels. Histamine is also responsible for the nasal congestion associated with the common cold and allergic response to pollen . Hence, Statement 1 is correct. Synthetic drugs, brompheniramine (Dimetapp) and terfenadine ( Seldane ), act as antihistamines . They interfere with the natural action of histamine by competing with histamine for binding sites of receptor where histamine exerts its effect. Now the question that arises is, “Why do above-mentioned antihistamines not affect the secretion of acid in stomach ?” The reason is that antiallergic and antacid drugs work on different receptors.
