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Staying well during a heatwave

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Worldwide, excess exposure to sun is the commonest cause of heat stroke - and it can occur in the UK, too, especially if you are not acclimatised to hot weather by spending gradually longer amounts of time in the heat before returning to the shade. Full acclimatisation can take up to three weeks, so be careful on unusually hot days – like today – after a period of colder weather.

Stay in the shade as much as possible, and avoid the hottest sun between 11am and 3 pm. Wear loose, lightweight clothes and a wide brimmed sunhat – or even a parasol. Avoid strenuous exercise and, if you feel hot, cool off in a shower as soon as possible. Eat a light diet, and never, ever, fall asleep in the sun.

Fluids are vital. Aim to drink fluids regularly throughout the day rather than just drinking when you feel thirsty, to maintain good hydration and pale wee. Avoid alcohol and excess caffeine.

Use sun screen when any part of your skin will be exposed to the sun for more than 15 minutes. Select a product with at least SPF16 and preferably higher. For children, an SPF of at least 30 to 40 is advisable. For full protection, look for products that screen out UVA rays, too. Apply sunscreen 15 to 30 minutes before exposure and use liberally – it takes 25g to cover the entire adult body properly. Unless otherwise instructed, reapply sunscreen every two to three hours and after swimming.

Watch out for sunstroke, which can occur when someone who is not acclimatised to hot weather gets too much sun, especially during the middle of the day when temperatures are highest. Increased humidity increases the risk of sunstroke as sweat cannot evaporate from the skin to cool you down. Increased activity levels in hot climates also increases the risks, as does wearing unsuitably heavy clothing, overeating, excess alcohol, and reduced ability to sweat (eg due to taking certain drugs – check leaflets that come with your medication). The elderly and young infants also find it difficult to regulate their body temperature and are more susceptible to sunstroke.

Symptoms of sunstroke usually start with heat exhaustion, in which there is profuse sweating, tiredness, muscle cramps, nausea and sometimes vomiting, faintness, unsteadiness and headache. If exposure to heat continues, body temperature rises and dehydration may set in. Sweating will reduce significantly and may stop altogether. At this stage, as well as the other symptoms of heat exhaustion, the affected person will feel hot with dry, flushed skin, rapid shallow breathing and weak, rapid pulse. They will become confused and disorientated. As body temperature continues to rise, drowsiness will occur followed by a seizure (fitting),  coma and even death if the condition is not urgently treated.  

Sarah Brewer graduated as a doctor from Cambridge University. Having worked in hospitals and general practice, she gained a Master's degree in Nutritional Medicine from the University of Surrey. She is the author of over 60 popular health books and writes widely on all aspects of health including complementary medicine. More from this expert.

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Nutrition Expert sources the latest information and advice from a range of qualified doctors, nutritionists and coaches. We always endeavour to have the most up to date information possible and publish new content weekly. However with the constant research in this field sometimes some of our older articles can become out of date. If you see anything that you believe needs to be updated please let us know via our Contact Us page