Should i be concerned if my 2 year old 33lb daughter has allergies (i gave her benedry per md) and now fever..can i give fever med?

See a doctor: By saying allergies i assume you mean your daughter has nasal congestion or URI like symptom. When she develops a fever, she needs to be seen and evaluated by a local physician to rule out bacterial infection, which requires antibiotic treatment. Both viral URI and allergies can get bacterial superinfection. It is safe to give your daughter fever medications while taking benadryl (diphenhydramine).