Hello. I Was Recently Prescribed Clindamycin For A Pilonidal Cyst

Hello. I was recently prescribed clindamycin for a pilonidal cyst and within a few days I started developing a rash on parts of my face and on my chest and upper back. I took a pill of clindamycin for last time about 15 hours ago. I've been using Benadryl to try to fight off the rash but I'm not sure how safe it is. So my main question is, will Benadryl help me? I'm not having any fever symptoms and no diarrhea just a rash and alot of itchiness. I didn't know the side effects until a couple hours ago (the doctor never told me any of them any neither did the pharmacist)