 [ Symptoms ] my doctor told me to take both zyrtec and zantac heartburn med  togther for my allergies will the combination help [ Disease ] i found the answer finally it is because zantac is a histamine blocker also that primarily works in the stomach and can work elsewhere but does not do well on its own zantac is an antihistamine primarily effective for the histamine receptors in your stomach they are called h 2 receptors the histamine receptors in your blood vessels & nerve endings are primarily h 1 receptors with some h 2 receptors when h 1 active anthistamines like benadryl or allegra are not sufficient to control hives zantac can be added for a little extra control alone it is not very good  here is a page of similar answers from doctors with more detail <link> zantac is an antihistamine primarily effective for the histamine receptors in your stomach they are called h 2 receptors the histamine receptors in your blood vessels & nerve endings are primarily h 1 receptors with some h 2 receptors when h 1 active anthistamines like benadryl or allegra are not sufficient to control hives zantac can be added for a little extra control alone it is not very good source healthtap <link>