Dehydration is the depletion of water from the body. It can be prevented by drinking plenty of water, especially during periods of physical exertion. One to five percent dehydration will make you lose your appetite, become sleepy and nauseated, and begin to vomit. As dehydration goes up to 10 percent, dizziness results. You will have headaches, difficulty in breathing, tingling of the legs and arms caused by poor circulation, indistinct speech, and, finally, an inability to walk. Still, 10 percent dehydration generally causes no permanent ill effects. When dehydration exceeds 10 percent, you will become delirious, spastic, almost deaf, and barely able to see. The skin shrivels and becomes numb. At temperatures above 90°F, dehydration over 15 percent is generally fatal. At 85° and less, the body can stand up to 25 percent dehydration. Dehydration is quickly cured by water—in fact, only water can cure it. When you are dehydrated, you don’t have to worry about how much water you drink or how quickly you drink it, or if the water is warm or cool. Cold water, though, will upset the stomach.