Is it okay to take allegra and benadryl (diphenhydramine) in the course of one day (24hrs) if allegra alone is not providing the relief i seek?

Yes: You will be ok, but I would suggest talking to your doctor if you are needing that much antihistamine to feel good. There may be other medications that will be better in this situation. Get well and have a great day!

Yes, but: For what do you seek relief? If you have nose/eye/ear symptoms related to allergy, then there are more effective treatment strategies compared with oral antihistamines. An Allergist can help with this. If you have uncontrolled hives, might also see allergist or dermatologist, but using higher doses of long-acting antihistamine is common. Read labels and be aware of side effects (like sedation)