24 hours after wasp sting and taking benadryl (diphenhydramine) the swelling is back to its max and hives again?

Please go to ER: That's a bad reaction to wasp sting, it might progress, keep epipen handy,and keep taking benadryl (diphenhydramine) better go to ER, and fix an appointment with an allergist later, good luck

Insect allergy..: Agree with Dr Al Hegab. It is important to know that bee allergy (which commonly occurs with wasps and other stinging insects) can be deadly. Hives that occur immediately after a sting must be addressed: both in the context of the emergent setting right after and later to address the underlying problem. Repeat stings carry greater risk and procedures are effective in generating tolerance.