Summer: From sunstroke to heat stroke: from when heat endangers your health

In view of the heat waves of this summer, the European office of the World Health Organization (WHO) warns to prepare for the high temperatures.

Summer: From sunstroke to heat stroke: from when heat endangers your health

In view of the heat waves of this summer, the European office of the World Health Organization (WHO) warns to prepare for the high temperatures. In the Mediterranean countries that are particularly popular with tourists, such as Spain, Italy and Greece, it has recently been hotter than 40 degrees, and further heat waves are imminent.

With global warming, the number of heat deaths is likely to increase from year to year, warned the director of the WHO Europe region, Hans Kluge. He referred to a recent study that found there were more than 60,000 heat-related deaths in Europe in the summer of 2022. In addition to fighting climate change, countries would therefore have to adapt to the new reality in the long term. What do heat waves mean for people? An overview.

A rule of thumb is: it becomes dangerous when, under certain conditions, the body absorbs more heat than it can release again. Because then the body temperature gets out of control and rises rapidly. This limit is very individual and depends on age, state of health, activity and habituation. At over 30 degrees, the body of many Central Europeans has significantly more stress to cool itself than at lower temperatures. It usually takes several days to get used to high temperatures.

Heat means hard work for the human body. Because the organism tries to keep its temperature constant around 37 degrees. Most cells, enzymes, proteins and the immune system then work optimally. In the event of extreme fluctuations, all of these processes are disrupted. If the human body temperature rises above 42 degrees or falls below 32 degrees, it can be fatal.

In order to counteract organ damage, the body increases its cooling system when it is hot and releases liquid and salts - the sweat. This cools the skin through evaporation. High humidity slows down this process. When the body is warmer than its surroundings, it can also radiate heat - like a lightbulb heats up its surroundings. When it's hot, blood vessels dilate, causing blood pressure to drop. The heart increases its pumping capacity, and breathing can also accelerate. Brain performance can decrease due to reduced oxygen supply.

High outside temperatures can put a lot of strain on the cardiovascular system. People with chronic pre-existing conditions in this area should therefore be particularly careful. As we age, body temperature regulation slows down and there are fewer sweat glands. Also, because older people are less likely to feel thirsty, they are at risk of becoming dehydrated. According to the Malteser relief service, even one to two percent too little water in the body can lead to headaches, tiredness, poor concentration and dizziness.

Among other things, sweat production is lower in children. Babies and small children in particular are therefore more likely to have heat complaints – dehydration is also a risk here. People who do hard physical work outdoors or who find it difficult to help themselves because of illness are also at risk when it is very hot.


If the head is exposed to direct sunlight for too long without a cap, hat or scarf, this can lead to irritation of the meninges. In severe cases, brain swelling occurs. Signs of this can be headache, nausea with vomiting, fever, sometimes also disturbances of consciousness and seizures.


When it's hot, the body's capacity to sweat can reach its limits. Then heat builds up: the body temperature rises quickly – often within 10 to 15 minutes – to over 40 degrees or more. As a result, the brain swells, causing headaches, changes in consciousness, or loss of consciousness. This is an emergency medical service case.

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Excessive heat causes blood pressure to drop. The result is a reduced cerebral blood flow, which can lead to a feeling of weakness, nausea and dizziness to unconsciousness. This is also an emergency.

heat cramps:

Anyone who does physical exertion in the heat, for example when doing sports or gardening, usually sweats profusely. This can lead to a lack of fluid and electrolytes such as sodium or potassium in the body. They help control nerve and muscle function. When there is a lack of electrolytes, the muscles react with cramps or muscle pain.

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If the sweat cannot evaporate sufficiently due to poorly breathable or tight clothing, it clogs the outlets of the sweat glands. The result is small, often itchy or burning blisters.