I have true allergy to benadryl (diphenhydramine) (had hives when taking the dye-free for a headache.) is allegra safe for me? and would it help my allergic reactions?

Yes: Allergy to Benadryl (diphenhydramine) is rare if at all present. Allegra is quite different from Benadryl (diphenhydramine) in structure and thus should be safe for you. Make sure you are not allergic to the gelatin on the Benadryl (diphenhydramine) capsules. Whether Allegra would work for you or not is another issue but it should be no less effective than benadryl (diphenhydramine).