What Causes Rash On The Face Of An Infant?

my 6 month old daughter has had a rash on her face for about 3 days it gets better and worse through out the day but doesn't seem to have a consistent cause. she has had a fever off and on since about 2 days before the rash started. i have changed her bedding i use only dreft baby laundry soap i have cut fruit out of her diet. i have been putting benadryl topical on the rash and have been giving her oral benadryl. all of her shots are current includeing the M.M.R. her last set of shots was about 2 weeks ago.