As heatwaves continue to hit the UK and heat-related health warnings come into force, people are looking for ways to cool down and reduce the risk of heat stroke – the most severe form of hyperthermia, in which the body temperature rises above 40°C.
Older adults, people with serious health problems, and very young children are most at risk. One reason for this is that the young and old have a reduced ability to dissipate heat.
Older people retain more heat than younger people because their sweat glands don’t work as well and their hearts don’t pump blood as efficiently, so less heat is lost through the skin.
Sweating is the most powerful way to remove heat from your body. When sweat evaporates, it takes the heat with it. In the heat, people can lose half to two liters of sweat per hour.
In temperatures where the air temperature is higher than body temperature, heat can transfer from the air to the body, posing an additional challenge in removing heat from the body.
Besides sweating, the other main way to lose heat is through vasodilation (widening of blood vessels) in peripheral tissues. In extreme heat, the skin may receive six to eight liters of blood per minute to help carry heat away from central organs.
The main purpose of the body’s response is to transport heat away from the major organs and the central nervous system, to keep their temperature as close to 37°C as possible.
Although sweating and dilation of blood vessels are effective, they are limited — especially when temperatures remain high for several days.
The best ways to lower your temperature are those that support the body’s existing systems for dissipating heat.
applying cold things to the body
Applying cold water or a cool damp sponge to the skin is effective in drawing heat out of the body. This is beneficial for people with limited mobility and the elderly.
Those who are able can take a cold shower. Evidence suggests that water of around 26 or 27 degrees Celsius is optimal. This is cold enough to draw heat away from the body, but not so cold as to trigger shivering, which would produce heat loss. (Immersion in very cold water can also cause cold shock.)
Studies conducted during the 2003 heat wave in France showed that cooling (using a mister, cool or cold baths or showers, sponge baths, mechanical fans or air conditioning) may be beneficial and may prevent heat-related deaths.
Ice or cold packs (a damp towel or cloth works fine) can be applied to the body. The groin, armpits, neck, forehead, wrists and torso are all areas that have lots of blood vessels close to the surface. The cooled blood can then flow back to the main organs to lower the core temperature.
Ice or ice packs should be wrapped in a towel or something similar to prevent skin burns. Applying and removing them every ten minutes reduces the risk of injury.
Partially filling a hot water bottle and placing it in the freezer for use at bedtime, or stuffing a pillowcase into a plastic bag and placing it in the freezer to cool while you sleep may also help at night.
fan
A recent study showed that fans can improve the evaporation of sweat, but not enough to reduce core body temperature. And this is even less when the ambient temperature rises above 33°C, or for older people and those with reduced ability to sweat.
Hot and cold drinks
Evidence from performance athletes exercising at 28°C showed that cold liquids, at refrigerator temperatures, were better at reducing core temperature than ice or temperature-neutral liquids at 37°C.
Drinking hot beverages activates the body’s cooling system, but if you haven’t drunk enough, it will cause the body to lose essential fluids, so cold beverages are best in this situation.
Shadow
All of these things are more effective in a cool shady area to increase the temperature gradient between the body and the ambient temperature. If you try these in the sun, they are likely to be less effective because the ambient air is warmer in the sun which means there is less ability to remove heat or it happens more slowly.
Overall, however, the evidence suggests that immersion in (ice) water is the most effective way to cool down – which can be done most easily at home by dipping the feet or hands into a bowl of cold water. Dipping in water is the way many animals in hot weather and climates lower their body temperature by standing in water, so it’s a good technique for humans too.
But if you are unable to do this, evaporation (mist and fan) is the next most effective method.
,Author: Adam Taylor, Professor and Director of the Clinical Anatomy Learning Centre, Lancaster University)
,disclosure statement: (Adam Taylor does not work for, consult, hold shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond his academic appointment)
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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