Heat Exhaustion vs Heatstroke Explained: How to Tell Them Apart and What to Do

Overview

Heat illness during extreme temperatures is a growing public health concern. The following summary draws on The Conversation article by Alison Purvis explaining how heat exhaustion and heatstroke differ, their symptoms, and how to respond quickly.

• Core difference: heat exhaustion keeps core temperature below dangerous levels, while heatstroke involves a failure of the body's temperature regulation and potential brain injury.
• Vulnerable groups: older adults, young children, and people with health conditions or dehydration are at higher risk.
• Management: cool down, hydration, rest; seek urgent care if confusion, collapse or seizures occur.
• Practical tips: monitor heat health alerts and take breaks, seek shade, stay hydrated during outdoor work or exercise.

Introduction

Extreme heat is a growing public health concern in the United Kingdom as weather alerts warn of heatwaves. This summary is based on The Conversation article by Alison Purvis that explains how the body deals with heat, and how to distinguish heat exhaustion from heatstroke and respond effectively.

How heat affects the body

The body keeps a core temperature around 37°C. When the surrounding air heats up, cooling relies on sweating and sending more blood to the skin. These cooling mechanisms have limits; high humidity can stop sweat from evaporating and dehydration reduces fluid to sweat and circulate blood. When cooling fails, heat illness can develop into heat exhaustion or heatstroke.

Vulnerability and risk factors

Heat illness can affect anyone, but risk is higher for older adults and young children who regulate temperature less efficiently. Underlying health conditions such as heart, kidney and respiratory disease, and medications that affect sweating, hydration, or blood flow further increase risk. Enclosed spaces like parked cars heat up rapidly and can trigger quick rises in body temperature, especially in the more vulnerable groups. Outdoor work or exercise adds extra heat from physical activity.

Heat exhaustion

Heat exhaustion occurs when the body is struggling to cope but core temperature remains below dangerous levels. Symptoms include heavy sweating, dizziness, headache, nausea, fatigue, cramps or feeling wiped out. It is often accompanied by dehydration as salty fluids are lost through sweat. Hydration helps but water alone may not be enough in very hot or humid conditions or with continued activity. Most people recover fully if cooled and rehydrated promptly, and it does not inevitably progress to heatstroke.

Heatstroke

Heatstroke happens when the body’s temperature regulation fails and core temperature rises, typically above 40°C. The key difference is the effect on the nervous system, with confusion, disorientation, unusual behavior, collapse or seizures. Heatstroke can damage the brain and other organs and can be fatal without urgent treatment. Measuring core temperature is helpful but not definitive on its own; rely on the whole clinical picture, not temperature alone.

What to do if someone is overheated

If you see symptoms, move the person to a cool place, loosen clothing, offer cool fluids if they are conscious, and start cooling with fans, damp towels or a cold shower. Most people improve within about 30 minutes of cooling. If the person becomes confused, has a seizure, or loses consciousness, call emergency services immediately.

Conclusion

Knowing the difference between heat exhaustion and heatstroke can save lives, particularly during heatwaves or in enclosed spaces. The Conversation article also highlights who is most at risk and practical steps to reduce risk in hot weather.