Allergy Rash?
How long before it disappears? I do not know what caused the rash. Maybe it was something you ate or detergent. I've never had an allergy to something before, but these roses are raised itchy causing concern. I know it is poison ivy or anything, inside and arms in front of the thighs just above the back and kness in areas of friction at all, so I do not think its summer heat. If food allergy – How long will the rash?
If it lasts more than a few hours you might check with your doctor. However, I have sensitive skin and get hives all the time. You could go to google and type of rash, maybe you can find a picture that can give you an idea of what could be.
Dog Health Care : How to Treat a Dog With an Allergy Rash