I'm allergic to sweat!
 

SERIOUSLY!...I don't know if this happens to anyone else but whenever i work out and sweat my face burns after. My cheeks and forehead are red for hours like i stayed to long in a tanning booth! I am very fair skinned but jeez! I used to think maybe its because i didn't drink enough water but i'm not sure anymore.

I have a similar problem, though I doubt you're allergic to your own sweat. I tend to break out in hives when I exercise. Do you get the same result if you're in a warm/hot shower for too long? Do you have allergies? If so, what do you take? I take 10mg of cetrizine (generic of zyrtec) in the morning and it helps a lot.

If that's not the issue, are you sure you just aren't working yourself too hard?

When I exercise hard, I sometimes get a fine rash on my arms that itches. Taking an antihistamine can help.

"During exercise, histamines are released. Histamines are proteins involved in autoimmune responses like an allergic reaction to pollen or dust. People who are sensitive to histamines can experience rashes, itching, and other allergic symptoms during exercise just like you are describing. Most of the time, the rashes appear on the chest and thighs, but they can appear on the neck or arms, too. Sometimes exercise also reacts with food allergies or medications (for example, antibiotics, pain medications, sedatives, tranquilizers, and diuretics) to cause the problem. The problem typically occurs more in cold weather than warm."

I think if you have Rosacea, sweat can make your face sting. The other thing is maybe if you use face products of any kind before working out, maybe they're reacting with your sweat and causing the stinging.

maybe you can see a dermatologist and they can tell you for sure?