Antacids suppress the symptoms of acidity and not the cause. They work by neutralizing the acid produced in the stomach i.e. they do not control the cause of the production of more acid.

Antihistamines are the drugs that suppress the action of histamine which is the chemical responsible for the stimulation of secretion of acids (example pepsin and HCl) in the stomach.

Thus, antihistamines are used over antacids for better treatment of hyperacidity.