Having itchy skin irritation, with redness and some swelling. It reallys comes out when I get hot?

Cholinergic hives. This is known as cholinergic urticaria when the small itchy hives appear during the cooling period after a rise in body core temperature. Antihistamines such as zyrtec (cetirizine) can usually prevent this from happening. This condition is not dangerous and often goes away after a few years. Do note that this does not apply to large hives (>1/2 inch in diameter).