C.D.
Hi there -
I have used the Children's Benadryl allergy medication on my boy when he was about 4-5 months old as well. He was allergic to regular formula (we later found out) and started breaking out with bumps around his face and body. He took the Benadryl and the bumps went away in a couple hours. (it did help him sleep as well). We tried not to use it unless we absolutely need to but he has never had issues with it.
Good luck!