When I was studying abroad in Australia (from Kansas) a year ago, I started getting a rash whenever I would go down to the beach. It was especially bad on my stomach, back, and legs, but it showed up everywhere but my face and hands. I finally made a dermatologist appointment this week and I wanted him to see the rash that I get when I am in the sun, so I stood outside for about 15 minutes before I went in to the appointment. He seemed excited, I guess, maybe he had never seen this in real life? But I had no idea what it was because I had never bothered looking it up. It only affected me in the summer and spring (probably because I wear long sleeves and pants already in the winter and fall) and the dermatologist said he thought it was solar urticaria. The only thing is, I'm looking up pictures online of this condition, and mine doesn't look the same as the pictures. I don't have big mountainous red spots (wheals?). I have a pretty even rash, like what it looks like if you get any other normal kind of rash. But other than the appearance, it is exactly as the text books describe. Any skin exposed to the sun becomes a rash, any skin covered by clothing does not. The rash appears within seconds or minutes and disappears within about an hour or two.
It seems kind of difficult to find real accurate information on solar urticaria because there isn't a lot of knowledge out there about it yet. Some differences I experience that I haven't really seen documented anywhere (maybe you can let me know if you share in these experiences) are things like this...
1. A period of time seems to need to go between rashes before I get one again. For instance, after going to the dermatologist, I went home to my parents house and tried to show them, but the rash wouldn't appear where it was the day before. It only appeared on my stomach and shoulders, which were not exposed the day before. And the day after that, I didn't get the rash anywhere. But it will come back, I know. I just don't know how long has to go between exposures.
2. Like I said above, the rash is splotchy, but not huge red wheals, it just looks like a regular rash. It is a bit raised (as regular rashes are) but it doesn't look abnormal.
3. It seems to happen really fast on my stomach and back (within 30 seconds or less) and my legs and arms take longer (10 to 20 minutes).

That's about all....At this point I'm just waiting for the blood tests to come back.....Some support/guidance/comments/insight please?