As the heatwave begins to grip the UK and the heat health alert is in effect, people are looking for ways to keep cool and reduce the risk of heat stroke – the most severe form of hyperthermia, with a body temperature above 40°C.

Older adults, those with underlying health conditions and the very young are at greatest risk. Some of this arises because the young and elderly have less efficient body systems to dissipate heat away from the body.

Older people hold heat more than young people because their sweat glands don’t function as well and their hearts don’t circulate blood as efficiently, so less heat is lost from the skin.

Sweating is the most powerful way your body can remove heat. As sweat evaporates, it takes heat with it. In the heat, people can produce between a half to two litres of sweat per hour.

In temperatures where the air temp is above the body temperature, heat can be transferred from the air to the body, which produces an additional challenge in removing heat from the body.

Aside from sweating, the other major way we lose heat is vasodilation (a widening of the blood vessels) in........

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