Dehydration is a condition characterized by the excessive loss of water from the body. In most cases of dehydration, the body also loses salt. Symptoms of mild dehydration include dryness of the mucous membranes of the nose, mouth, and throat; reduced ability to sweat and urinate; and doughy skin. In severe dehydration, rapid loss of salt and water leads to fast heartbeat, low blood pressure, shock, and even death.