Allergic reaction

Patient: My daughter is a 1 year old and she is allergic to carrots. She was given food that we did not know had carrots in it and she has a really bad diaper rash now. We are changeing her a lot and using cornstrach powder on the rash. Can we give her Benedryl to help with the rash? Is there anything else that we can do for her? She keeps waking up from the rash.