Which symptom may help identify dehydration in an adult?

Dry lips are a classic sign of dehydration in adults. When the body lacks adequate fluids, it can lead to a reduction in moisture levels across various tissues, including the lips. This dryness occurs because the mucous membranes in the mouth and lips dehydrate, making them feel dry and cracked. It serves as an external indicator of the body's need for hydration. Recognizing dry lips as a symptom can prompt further evaluation of a person's overall hydration status and lead to appropriate interventions, such as encouraging the intake of fluids.

In contrast, while frequent headaches may occur in some cases of dehydration, they are not as specific or reliable a diagnostic indicator. Visual disturbances can arise from various underlying health issues and are not directly linked to dehydration. Excessive sweating, although it indicates a loss of fluids, is more about fluid loss than it is about the body's current hydration status. Dry lips provide a clear and immediate physical sign of dehydration that can be easily observed.