By Live Dr - Tue Sep 02, 12:58 pm

Written by Dr Charlie Easmon, specialist adviser in travel medicine

What is heatstroke?

Heatstroke is a condition in which the body becomes overheated in a relatively short space of time. This can be a life-threatening condition, requiring urgent medical attention.

Abnormally high body temperatures (hyperthermia) may occur in several different circumstances, such as:

  • classic heatstroke (also called sunstroke: a little misleading because the condition can arise without the direct effect of the sun) when, typically, the skin is flushed, red and dry.

  • heatstroke caused by exertion, which often occurs in conjunction with pronounced physical exertion, eg sports activity.

  • in extensive burns (including sunburn), where the sweat glands have been damaged or destroyed.

  • in a number of less common medical conditions, such as overactivity of the thyroid gland (thyrotoxicosis).
  • The first three in the list are of special interest to the traveller.

    When can heatstroke occur?

    Heatstroke occurs when the body cannot dispose of excess heat in the normal way. Heatstroke and fever can be distinguished as follows:

  • fever, in which the body’s mechanism for regulating temperature is functioning and set at a higher level. The patient is, typically, flushed and bathed in sweat.

  • primary hyperthermia (for instance, heatstroke), where temperature regulation is either partially or totally out of action. The patient often sweats only a little or not at all and the skin is flushed red, hot and dry.

What puts the traveller at risk of suffering heatstroke?

  • Surroundings with high temperature, high humidity and strong sunlight (typically in the tropics).

  • Too much physical exertion (eg sport), particularly in the above conditions.

  • Extensive sunburn, particularly in a hot and humid climate.

  • Lack of fluids/salt in hot (particularly tropical) surroundings.

  • Excessive alcohol consumption under the same conditions.

What can you do to help yourself?

  • It is important to get used to heat and humidity slowly, particularly before physical exertion. This acclimatisation to the tropics can typically take one to three weeks.

  • Make sure you drink plenty of salty liquids (at least 3 to 5 litres a day, but not alcohol). In very hot conditions you may need to drink much more and a good tip is to start the day by drinking at least two litres!

  • Make sure you supplement your salt intake (for example by eating crisps and/or taking salt tablets).

  • Wear light, airy, loose-fitting clothing (light cotton).

  • Be careful if you undertake any hard physical exertion, particularly if your fluid/salt intake is low.

  • Stay in the shade or, if possible, in an air-conditioned environment.

  • Take frequent dips in cool water (sea or pool), particularly if you are sunbathing a lot.

When does heatstroke become critical?

  • Body temperature around 41°C (measured in the rectum).

  • You feel increasingly unwell, tired and dizzy, and your head may hurt and you may feel ‘distant’.

  • If your skin becomes flushed red and dry (ie perspiration is reduced or not functioning).

  • You produce less urine, which is of a dark yellowish colour (which indicates a shortage of fluid).

  • You become less alert, with a tendency to faint, and experience confusion, impairment or loss of consciousness and convulsions.

  • At temperatures above 41°C the situation starts to be serious. At temperatures above 42°C cell damage to the brain, liver, kidneys and skeletal muscle often occurs as well as bleeding disorders.


If a person suffers from heatstroke it is important to put them in the shade and preferably in a cool environment (ideally an air-conditioned room at a temperature of 15 to 18°C).

  • The patient should be undressed and made to lie naked, or covered only by a thin sheet.

  • If the patient’s temperature rises to 39.5°C, and the skin is still dry and burning hot (or with only very slight sweating) they should be showered with cool water (15 to 18°C). You can also put the person in a bath of cool water while massaging the skin to increase circulation. Another possibility is to cover the patient with wet sheets or towelling, changing them often, preferably in combination with an electric fan, or something similar, to bring the temperature further down.

  • Do not use water cooler than 15°C because this will restrict heat loss as the blood vessels in the skin will contract.

  • If possible the patient should be taken to a doctor, or better still a hospital, as soon as possible. A person with heatstroke often needs oxygen, a drip (fluid infusion into a vein) and sometimes medication.

Who is particularly at risk of suffering heatstroke?

  • Elderly and often weak or fragile people with a low fluid level.

  • People who are overweight.

  • People with cardiovascular or lung diseases.

  • People taking certain types of medication, such as anticholinergics (which prevent sweat production) and beta-blockers (which reduce the blood circulation to the skin).

  • Infants and small children.

  • Pregnant women (particularly if their fluid/salt levels are low).

  • People under the influence of alcohol.

  • People who play a lot of sport without taking sensible precautions, such as drinking plenty of fluids.


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