Hives

I got hives yesterday and they are still here. I have no idea why I got them. They suck! This is the first time I have ever gotten them. I could barely sleep, they itched so much. Ughhh!!! I don't know what to do. I have an appointment with the doctor later today. Oh and they are on my face as well. Called off work this morning and I actually wanted to go today. My back is covered with them and my tummy and under my chin and neck and back of my neck and legs. Oh this is horrible! How long do these things last???