I was on call recently and had a couple of late night phone calls about fever.

 

In both instances the parents were concerned that their child was shivering noticeably and seemed pale. After explaining fever and shivering it seemed like a good topic to discuss here.

 

When one gets a viral or bacterial infection it invades the body and causes tissue injury or damage.

 

This stimulates our immune system to produce pyrogens or cytokines. These polysaccharide-protein compounds are carried to the brain which affects the temperature regulating portion of the brain called the hypothalamus. In response to the pyrogens the hypothalamus will raise the body’s temperature (fever) to help fight the infection. Fever plays a vital role in the body’s defense system as it stimulates the production and release of white blood cells. This, in turn, aids in their mobility and effectiveness against the offending organism. Fever also directly kills viruses and bacteria.
 

Fever is actually a GOOD thing in most instances.

 

When the pyrogens make their way to the hypothalamus they inhibit the heat sensing neurons in the brain and excite the cold sensing ones. This tricks the brain into thinking that the body is actually cooler than it really is. In other words, the core temperature may be elevated but the brain thinks the periphery is cold. To adjust, the brain causes the muscles to “shiver” which generates heat and is a way of raising the body’s temperature.

 

After some time things re-equilibrate and the hypothalamus realizes that it has been “duped”.

 

The overall body temperature is actually higher than normal. To correct for this, a message is sent to the blood vessels near the skin to dilate and increase blood flow to the skin as well as sweating—both of which help in getting rid of excess body heat by evaporation. This causes flushed and sweaty skin, usually seen when a fever “breaks”.
 

In summary, fever is not a bad thing although it can cause much angst for parents

 

It serves an important function in our body’s defense mechanism. In the early stages of an infection it is common for the patient to seem pale and cold, and have the shivers. This usually means that the fever is on its way up. After awhile, the same patient may then feel hot and become flushed and sweaty. These are signs that the body is functioning as it should to help fight the infection.