Prickly heat is a skin rash caused by trapped sweat under the skin.
Sweat can become trapped when the narrow ducts through which sweat travels to the surface become clogged. Prickly heat tends to be more common in warmer, more humid climates. The condition usually appears on the torso and thighs. The following are the most common symptoms of prickly heat. The symptoms of prickly heart may resemble other dermatologic conditions.