3 times in the last year I've had a strange reaction where I start getting redness and a burning/itching feeling at my joints. It comes on pretty suddenly. It usually starts at my knuckles and spreads to my elbows, shoulders, knees, toes, and also my face and ears. I don't think it's technically a rash, more like some sort of vascular reaction. There are no bumps, just flat, red splotchy areas, and it goes away after 30-60 minutes.
I've taken Benadryl at the onset thinking it was an allergic reaction, but I really can't tie it to anything in particular. The only thing in common with the 3 reactions was that it was fairly warm on those days. The first reaction happened when I was a few months pregnant. The second was about 8 months later, and the third happened a few days ago. I'm really confused about what it could be. Any ideas??