heat rash

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An inflammatory skin condition caused by obstruction of the ducts of the sweat glands, resulting from exposure to high heat and humidity and characterized by the eruption of small red papules accompanied by an itching or prickling sensation.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun obstruction of the sweat ducts during high heat and humidity