Which of the following is a sign of heat exhaustion?

Heat exhaustion is a condition that occurs when the body overheats and is typically characterized by an excessive loss of water and electrolytes. This often results in symptoms related to the body's efforts to cool down. Pale, usually sweaty skin is a key indicator of heat exhaustion. As the body attempts to regulate its temperature, it often increases perspiration, leading to cool, clammy skin that may appear pale.

In contrast, the other options describe symptoms associated with different conditions. Bright red skin is more commonly associated with heat stroke, which is more severe than heat exhaustion. Dry mouth and thirst indicate dehydration, which can accompany heat exhaustion but are not defining symptoms. Excessive energy is contradictory to the fatigue and weakness often experienced in heat exhaustion or other heat-related illnesses. Recognizing pale, sweaty skin as a sign helps in identifying heat exhaustion, enabling timely intervention to prevent more severe heat-related illnesses.