Hives? Rash? Inflammation?

My bro-in-law broke out in a rash two days ago. At least, he said it was a rash that itched. My degree is in animal sciences so my ideas on human conditions were limited, but it sounded like an allergic reaction. But he couldnt think of anything he'd come in contact with that was unusual or new. Benadryl helped the itching but not the welts. He went to the dr yesterday morning and without evening looking at his body, the dr said it was hives and prescribed him two antihistamines and a steroid.

We went over last night and I was horrified. He showed me his arms and stomach and his entire body is covered with red welts that are significantly raised with a noticeable dark red outer ring, and then outside that is a nearly white ring. Almost like ringworm but not on the same scale and not flaky. Some of the welts are a good 6 inches in diameter. He says they are tender to the touch and what concerns me most is that towards the center of them there seems to be bruising...continued below..

almost like hematoma. The bruising has spread across the central mass of the welts and into the palms of his hands as well. He's covered head to toe with these things and I'm greatly concerned the dr didn't even bother to lift his shirt to have a look- unless his condition worsened rapidly from after the visit to when I saw him. Physically he says he feels mostly fine, just sluggish, which could be the antihistamines. I offered to take him to the hospital but he didn't want to go because he said people would be staring at him.

I've never seen anything like this and can't find anything similar on the web. Suggestions as to what it could be?

GET HIM TO A HOSPITAL...ASAP

That's harsh. Only thing I know of is poison. I don't know of many rashes so of course that's the only thing coming to mind. Sorry though I hope he feels better soon.

A few years ago, on Mother's Day, my family spent the day outisde around alot of grass and flowers. Later that night, I noticed a few round bumps that were itchy. I assumed that they were some kind of bug bites. By the next day, I was covered in them and I also starting to get "wheels" - red raised lines that were also itchy. Sometimes, my back and shoulders was so covered in wheels, it looked like I had been whipped. Scratching the hives only made them worse. I had them all across my back, under my thighs, on the backs of my arms, on my chest. Some days, I was so itchy I thought I was going to lose my mind! Other times, I didn't even know I had them until a friend pointed them out.
Finally, I discovered that it was an allergic reaction. I, too was prescribed steriods and antihistamines, which offered some relief. It continued to appear, off and on, for a few months and then lessened in frequency and severity, but still continued for several more months. Certain weather seemed to cause it to worsen (like humidity). Eventually, it just stopped happening.
The unusual appearance of the hives you describe would make me want to have a doctor take a second look, though.
I also never had any tenderness on the hives or wheels.
I'd would be interested in an update!

A lot of skin rash information at the source below. It may help the diagnosis of the skin rash.