Allergies that result in hives and itching are very common. Unfortunately a majority of the time the cause is not found. A doctor will probably tell you to try switching detergents and soaps because this can be the cause. I had a period of about 6 months where I would get unexplained hives. Never was able to find a cause but my doctor had be start taking an everyday allergy medication like Zyrtec or Claritin. Once I started that the hives went away and haven't came back.
I would first see if you can find a common irritant you can eliminate. If not try taking Zyrtec or Claritin.
I would make an appointment with your family doctor. Tell your doctor what has been happening. After examing you, your doctor will probably suggest
that you have an allergy test. He or she will probably give you a referral to
an allergist. Myself, I wouldn't self medicate with Zyrtec or Claritin if you
don't know what you're allergic to. I have allergies but I had an allergy
test many years ago now and that's how they were discovered. You say
you're taking Benadril, but it keeps on coming back. I would really suggest
a visit to your family doctor. Good luck in finding out what's going on.