Fever due to heat exhaustion: what to know

Heat exhaustion develops when the body struggles to lose heat, often after exertion or time in a hot, humid setting. Sweating removes water and salts, so dehydration may develop alongside symptoms. A person may feel faint, clammy, unusually tired, or headachy, and urine may become dark. Heat intolerance or a sudden change in sweating can be useful context. Symptoms should improve with cooling and rest; worsening illness needs urgent assessment because heat stroke can affect the brain and other organs.

Move to shade or an air-conditioned place, loosen extra clothing, and cool the skin with wet cloths or a fan. If fully awake and able to swallow, give frequent small sips of water or an oral rehydration drink. Stop exercise and remain with the person while they recover. Do not give drinks to someone who is confused, vomiting repeatedly, or unable to swallow safely.

Call emergency services for confusion, collapse, seizure, severe breathing trouble, worsening drowsiness, or inability to drink. Seek urgent help if cooling and rest do not bring clear improvement, or if vomiting prevents fluid replacement. People who are pregnant, very young, older, or medically vulnerable need a lower threshold for assessment. Do not let someone with ongoing heat symptoms return to strenuous activity that day.

Ask whether the episode was heat exhaustion or another illness, how to rehydrate safely, when activity can restart, and how medicines or medical conditions may affect heat tolerance. Describe the setting, exertion, sweating, fluid intake, and recovery.