WHAT IS A FEVER?

Fever is a body temperature that is greater than 100.4 F.  Although we tend to think of fever as a response to infection, there are other things that cause a fever, but we’ll keep it simple in this post and talk about fevers related to infections.

A fever is caused by your body responding to a foreign invader such as viruses, bacteria, and, less commonly, fungi.  When you are exposed to these invaders they can stimulate a part of the brain to raise your temperature.  Your body responds to this signal by shivering and narrowing (constricting) the blood vessels near the surface of our bodies.  Shivering involves small, rapid muscle movements that increase heat (much like when you exercise and warm up).  When you exercise and get flushed your body is increasing blood flow to the blood vessels near the skin to allow release of heat (the blood vessels dilate or get bigger to allow this to happen).  When those blood vessels narrow (constrict) in response to the foreign invaders they are trying to hold onto the heat that those shivering muscles are generating!  Most of the time a fever is a perfectly orchestrated response to infection.

WHAT IS THE BEST WAY TO MEASURE A FEVER?

We define a fever as a temperature over 100.4 F (38 C).  The most accurate temperature is obtained rectally, especially in younger children.  Oral, axillary (armpit), and temporal scan thermometers are also used, but will result in a lower number than a rectal temperature.

HOW DO YOU TREAT A FEVER?

Fevers are controlled by medications called antipyretics.  These include tylenol and non-steroidal anti-inflammatory agents like ibuprofen (Advil or Motrin), and Aleve.  These medications are available over-the-counter and can be dosed based on directions on the bottle.

Having a fever makes you more prone to dehydration, so it is important to drink plenty of fluids and get plenty of rest.

WHEN DO WE WORRY ABOUT A FEVER?

Development of a fever is a symptom of an underlying infection. The height of the fever is not necessarily something to be concerned about. Small children have a high metabolism and a large body surface area, so they can generate high fevers (103-104 F) rapidly. A fever is worrisome when it is accompanied by abnormal behavior and lethargy, certain types of rashes, inability to swallow, difficulty breathing, dehydration or occurs in a someone with a weakened immune or partial/no immunizations or under 3 months of age.  These symptoms should prompt medical evaluation.

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