so two weeks ago i put differin on my neck because I was getting a pimple there. The next day I saw a tiny rash forming and bought some benadryl itch stopping cream and the rash grew to cover my whole neck. i kept putting on the benadryl cream but it burns every time i put it on. then it started to go away. i wasnt sure whether or not the differin caused the rash or the duac I also use. so i put differin on again (i know, not smart) on my neck and for the last week I have had a huge rash on my neck. it had bled a few times. what should I do? it really burns and itches every morning when I wake up. my whole neck is red and splotchy.