Both antiacids and antiallergic drugs are antihistamines but they are antihistamines but they cannot replace each other . Explain why ?

Explanation

Drugs designed to cure some ailment in one organ in the body do not affect the other because they work on different receptors. For example, secretion of histamine causes allergy. It also causes acidity due to release of hydrochloric acid in the stomach. Since antiallergic and antacids drugs work on different receptors, therefore, antihistamines relieve allergy while antacid remove acidity