Body Temperature

The average human body temperature, measured under the armpit, is 36.5 degrees Celsius. Studies on many healthy individuals show normal temperature can range from 36 to over 37 degrees Celsius.

Humans, along with other mammals and birds, are warm-blooded, maintaining a constant body temperature regardless of environmental changes. They can endure very low winter temperatures or over 50 degrees Celsius in summer shade without their body temperature changing.

The main "conductor" responsible for maintaining body temperature is located in the brain, specifically the hypothalamus. This temperature regulation center functions like a thermostat, automatically maintaining consistent temperatures in devices, machines, or homes.

Operating on a similar but more complex principle, the brain’s "thermostat" sends signals via nerves to reduce heat production and increase heat loss when body temperature rises. If the temperature drops, the signals reverse, reducing heat loss and increasing heat production.

Body heat is generated by metabolizing food in the cells of organs and tissues. At rest, the liver (20% of total heat), brain, and heart produce the most heat. The greatest heat is generated by muscles during activity. Blood circulation evenly distributes this heat throughout the body.

Heat is continuously produced but also constantly lost from the body’s surface to the environment. When heat production equals heat loss, thermal balance is maintained. If heat production increases, such as during intense muscle activity, the brain’s thermostat activates: skin blood vessels dilate (causing a flushed face), increasing blood flow to the surface. To facilitate this, the heart works harder and faster.

The role of blood vessels in temperature regulation can be compared to heating pipes, with the skin acting as a radiator, releasing heat to a cooler environment. If heat production is excessive, radiation alone is insufficient, and the thermostat triggers increased sweating. Sweat evaporation significantly enhances heat loss.

Body temperature is typically measured by placing a thermometer under the armpit. Before use, the thermometer should be shaken down and the mercury level checked. Measuring in the rectum is more reliable than under the armpit and is used for abdominal inflammation or in young children. Rectal temperature is 0.5 degrees Celsius higher than armpit temperature. If it exceeds armpit temperature by more than one degree, it may indicate abdominal inflammation or poor measurement technique.

Oral temperature measurement is used only in adults and is rare in our country. The thermometer must be cleaned, disinfected with alcohol, and dried before use. It is placed under the tongue, and breathing is done through the nose to avoid cooling the thermometer, which would skew results. Oral temperature averages 37.2 degrees Celsius.

Elevated body temperature, also called fever, is not a disease but a symptom of various conditions, like pain or dizziness. Slight temperature increases are normal, often occurring during intense physical exertion, such as heavy work or demanding sports, rising by 1 to 2 degrees Celsius or more, especially if measured rectally. Emotional stress can also cause significant temperature increases.

In many diseases, elevated body temperature is beneficial, promoting faster antibody production to fight pathogens. Intentionally induced fever is used to treat some conditions. The positive effects depend on its duration.

Excessively high temperatures can be dangerous. At 41 degrees Celsius, body cells begin to be damaged. A person can survive 42 degrees for only a few hours and higher temperatures for mere minutes.

Newborns and infants in their first months are highly sensitive to environmental temperature changes. Overheating or cooling is more common than in older children or adults. High temperatures in infants are not always due to infections, which parents often fear. Overheating from warm rooms, excessive clothing, or hot water bottles can cause heat accumulation, as newborns cannot regulate temperature like adults.

Body temperature rises in newborns because sweat glands do not yet produce sweat in the first month. Despite high body temperatures, newborns do not sweat, and since excess heat is only removed through sweat evaporation in high environmental temperatures, urgent cooling measures are needed to prevent death.

It is incorrect to assume elevated body temperature must be immediately reduced to normal. Fever is a defensive response, and rapidly normalizing it can weaken the body’s defenses.

High temperatures should be managed only when they risk damaging the body, regardless of the underlying disease. A person with a fever should not follow a starvation diet but eat easily digestible, vitamin- and protein-rich foods in small, frequent meals.

Very high temperatures must be quickly identified and treated. First aid knowledge is crucial, as actions before a doctor’s arrival can save lives. Any armpit temperature above 41 degrees Celsius is considered very high (hyperpyrexia).

When body temperature exceeds 41.7 degrees Celsius, the body’s thermostat fails, temperature regulation collapses, sweating stops, and temperature continues rising. Only rapid cooling can prevent death. Once the temperature drops below the critical threshold, the thermostat resumes function, and the body regulates its heat.

When heat production is less than heat loss, the body cools, and temperature drops. Prolonged exposure of skin to low temperatures reduces blood flow, impairing skin nourishment and causing localized damage or frostbite, most common on exposed areas like the nose, ears, or fingers.

Some individuals have a normal temperature below 36 degrees Celsius, but low temperature can also indicate conditions like starvation, prolonged diarrhea or vomiting, extended diving (especially in children), chronic diseases (e.g., diabetes, anemia, brain tumors, brain hemorrhages), or reduced thyroid function. Acute alcohol intoxication and poisoning by phenol, sedatives, phosphorus, or atropine also lower temperature.