What is the hallmark of heat exhaustion?

The hallmark of heat exhaustion is persistent sweating. This condition occurs when the body loses excessive amounts of water and salt, primarily through sweat, in response to high temperatures, excess humidity, or strenuous physical activity in heat. As the body attempts to cool itself, sweating typically increases, leading to moisture on the skin.

While confusion and altered mental status may arise as heat exhaustion progresses, they are not defining features of the condition. Similarly, absence of sweating is more characteristic of heat stroke, where the body's ability to cool itself fails completely. Lastly, high blood pressure is not a typical indicator of heat exhaustion; rather, heat-induced stress often leads to a drop in blood pressure due to dehydration and cardiovascular strain. Thus, persistent sweating remains the key feature of heat exhaustion, indicating the body's response to overheating.