My 4 year old has strep throat and has been on amoxicillin for 6 days. Today she has a very sniffly nose, is it safe to give her children's Benadryl (diphenhydramine)?

Yes it is safe. Yes it is safe to give antihistamine.I prefer Laratidine syrup as it is once a day and not or Cetrizin as these are over the counter and have to be given only once a day,Loratidine is non sedating and Cetrizine may be slightly sedating as compared to Benadryl (diphenhydramine)