Hi, I Have Chronic Hives And Sometimes My Face Swells

hi, i have chronic hives and sometimes my face swells up. I woke up this morning and my face looked like a balloon. I took the pills that i have been taking for almost a year now and nothing changed so i took more. Also i took a little more later when nothing changed. I called my doctor and he called in prednisone. i took it about 40 minutes ago and i just am wondering how long it generally takes for the pill to kick in and the swelling to go down. I took 2 20MLG pills.