Thermoregulation is the name given to the process that allows the human body to maintain its core (or internal) temperature even when the surrounding temperature is very different. Normal body temperature of a healthy individual is considered to be 98.6 degree F (37 degree C), and is lowest in early morning (around 6 a.m.) and highest in late afternoon (4 to 6 p.m.). Also, body temperature rises normally in response to certain conditions, such as physical activity and the humidity in the environment. Body temperature is controlled by a region of the brain called hypothalamus by adjusting heat conservation, production, and loss. There are two ways in which this system can malfunction. In an excessively hot environment (heat stroke) or an adverse reaction to some medications (synthetic hormones, antidepressants, cocaine etc.) the body overheats through undesirable retention or over-production of heat that it cannot dissipate. This is called hyperthermia and is different from fever. In fever or pyrexia, the setting of the hypothalamic thermostat itself changes and the body increases its own temperature through both actively generating and retaining heat.
If the body is invaded by infection or allergens or malignancies, the body’s defences need extra help, they send out chemicals (pyrogens) that travel up to the hypothalamus altering its ‘set point” to increase body heat. Increasing the heat allows for a number of things. The white blood cells multiply and travel faster to the site of invasion and chew up the attackers more efficiently. Toxins that the bacteria or virus produces may be neutralized by the heat as certain proteins unravel with any changes in temperature. High temperature by itself disables certain bacteria. Once the battle is won the temperature setting goes back to normal.
Understanding this mechanism allows us to intervene rationally when your child has a fever.
Firstly, it is important to record temperature correctly. Remember that rectal temperature is the closet value to the body’s core value. A rectal temperature above 37.5 – 38.3 °C (99.5–100.9 °F) usually warrants attention. Always wait for 20 to 30 minutes after your child finishes eating or drinking to take an oral temperature, and make sure there’s no gum or candy is in your child’s mouth. An armpit temperature is usually 0.5°F (0.3°C) to 1°F (0.6°C) lower than an oral temperature. Forehead temperature and plastic strip thermometers are not reliable. Glass thermometers have been replaced by digital thermometers which are accurate.