Saturday, 29th June 2024

Heat Exhaustion

The recent tragic death of Dr Michael Mosley, the very high temperatures in Mediterranean countries  and the enormous death toll on the 2024 Hajj have brought the problem of heat exhaustion into our awareness. Even though  we consider ourselves lucky when we have above normal ambient temperatures, we do need to be aware that very hot weather can be a threat to our health, particularly when we exercise in the heat. After all we do get a limited number of very hot days in the UK – and we do take Mediterranean holidays.

What is Heat Exhaustion?

Heat exhaustion the condition of bodily overheating. The body’s heat production combined with environmental heat decide your core temperature. This is your body’s inner temperature. Your body needs to regulate heat gain in hot weather and heat loss in cold weather to keep a core temperature that’s typical for you. The average core temperature is about 98.6 F (37 C).

In hot weather, your body cools itself mainly by sweating. The evaporation of your sweat regulates your body temperature. But when you exercise strenuously or otherwise overexert in hot, humid weather, your body is less able to cool itself efficiently. When the ambient temperature is high, particularly when humidity is also high, these protective mechanisms may not be enough to deal with the excess heat production from exercise. The body’s core temperature rises and heat exhaustion followed by heat stroke may result.

Heat stroke occurs when core body temperature reaches 104 degrees Fahrenheit (40 degrees Celsius). This a serious and dangerous condition and calls for urgent treatment.


These include thirst, heavy sweating, faintness. dizziness. fatigue, a weak rapid pulse, muscle cramps, nausea and headache. Paradoxically the skin may feel cool, but damp. As the condition progresses from this earlier stage of heat cramps, confusion followed by loss of consciousness heralds the onset of heat exhaustion and heat stroke.

Risk factors

  • Age: Both the very young and the very old are more prone to heat exhaustion.
  • Medication: Some medicines can affect your body’s ability to stay hydrated and respond properly to heat. These include some drugs used to treat high blood pressure and heart disease such as beta-blockers and diuretics, antihistamines, tranquilisers and some illegal drugs such as cocaine and amphetamine. Both caffeine and alcohol have diuretic properties – ie they make you pee more.
  • Obesity: Fat acts as an effective insulation jacket.
  • Sudden rise in ambient temperature: This prevents the opportunity for acclimatisation.
  • Behavioural factors: These include inadequate hydration – not drinking enough – over dressing and drinking alcohol.


Mostly this a matter of common sense. Wear appropriate, light, light coloured and well ventilating clothing in the heat, drink more that you might usually do and be careful about increasing physical exertion. Stay out of direct sunlight and apply sun-screen to exposed areas. If strenuous effort is necessary, for instance for soldiers on exercise or for competitive athletes, warm up and when possible prepare with acclimatisation. This involves gradually increasing exercise levels after entering an unusually hot environment and takes about two weeks to help your temperature control mechanisms to adjust to exercising in the heat.


Lesser degrees of heat exhaustion are easily managed by resting in cool or air-conditioned spaces, drinking plenty of fluids, removing unnecessary clothing, fanning and tepid showering or bathing in cool water. (Cold showers or baths provoke constriction of the blood vessels supplying the skin and delay excess heat loss).

Heatstroke is a medical emergency which merits immediate medical treatment usually with admission to hospital and intravenous fluids.

Enjoy your summer!!


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