About 20 years ago after a long period of stress I suffered a major bout of hives (the blister kind, not the red rash kind).  My face  would swell up, including my eyes, and hands and feet and everything was swollen.  I took large doses of Motrin and Benedryl and after about 9 months they went away.   Now, just about a year ago, I started getting the red rash spot type of hive.  My allergist tells me there are two types. One is very near the top of the skin and one is far below.  After some blood testing she was able to determine that I have a predisposition in my blood for hives.    Check with your doctor, you could have the same thing.  Right now I'm on Zyrtec twice a day.  It seems to help.