My Girlfriend Has Had Hives For About Six Weeks. Steroid

My girlfriend has had hives for about six weeks. Steroid shots had no effect. A series of steroid pils had the all but gone and then they came back full force a day later. She is on Venlafaxine from her psychiatrist. Today her PC put her on Wellbutrin and Hydralazine for her hives. What would Hydralazine do to help? it is for High blood pressure and her nurse said her BP was a little low. I also found a strong reaction between her Venafaxine and wellbutrin when I checked drug interaction chart