@ddljohn-- Itching is a very common side effect of diltiazem cream. But if the itching is severe and constant, and if you also develop a rash, you might be allergic. You need to tell your doctor immediately in that case.
I'm allergic to diltiazem. When I first started using it, I had itching but my doctor had warned me about it so I didn't get worried. But within days, the itching got worse and I also developed a rash. When I told my doctor about it, he asked me to stop using the cream. He prescribed me a different cream for anal fissures and I had no problems with that cream.
So if the itching is mild, then don't worry. But if it's severe, call your doctor.