Why is it that when i get a little hot my body starts to itch. although the itching stops when i start to sweat?

Heat and itch: It isn't unusual for itching to occur when the body heats up as dilation of skin capillaries occurs. Moistening of the skin can relieve the itch as sweating cools off the skin. Rash is another response to body heat for some people.

The broad category: Of this phenomenon is called cholinergic urticaria. With change in body temperature, either from exercise or ambient temperature, the body's mast cells release histamine which causes itching. The stopping of itching when sweating is unusual as many say it is actually sweating that causes/contributes to the itching. An allergist/immunologist can help sort this out if you want but ok to watch, too