Rashes after body heats up?

[wickitom]

Whenever my body heat ups I get these red bumps and rashes on my chest and back area.  It only happens after a really hot shower, hot tub, exercise, whenever my body heat goes up.  A doctor told me I was allergic to the cold air.  Does anyone have any ideas why would this be happening?

Tom

[borninquisitive]

When I was a youngster, I used to requently get heat rashes. When my mother learned of this, she took care to buy me cotton (breathable!) shirts and discontinued use of fabric softners.

[Cassilee83]

A couple of years ago I woke up covered in hives... It was 102 degrees out and our C/A was broken. I found out that I was having a reaction to heat.  anytime I took a bath, went tanning, took a shower, went for a walk outside when it was cold and my body got hot, sat in a hot tub I was covered in welts. I mean one welt would cover the top of my thigh.  My doctor told me that it may sound weird but it can be a reaction to stess (parents divorce).  He told me to take benedryl before I did any of that.  At first it made me sleepy then I built a tolerance and it worked very well.  Now i only get really itchy if I'm walking and the air is cooler around me. but no hives or rash anymore.