Hubby has swelling all over body arms/legs/ankles. Went to ER. Heart/kidneys/lungs all fine. No answer. Gave anti inflammatory and sent home. Benadryl helps but he can't stop it. Must take every 6 hr. Primary had no answer. Out of town 4 work. Help.?

Go to ER. This calls for a second opinion if nothing else. If there is any problem with his breathing, go back to the ER NOW. If just a little uncomfortable, call the doctor who is on call for your vacationing primary. Best wishes .
Options. Would follow up with a Rheumatologist.
This sounds like one of a couple of rheumatological diseases. As it seems to have responded to anti-inflammatory.

If not that then Allergist to assess for the reason he needs Benadryl, which can be sedating. I might try OTC Zyrtec, Allegra, or Claritin instead.

These are 2 ideas but certainly I don't have all of the information.