Fever is one of the most common medical complaints of childhood.  Almost all children develop an elevated body temperature several times per year.  In most cases, the source of the fever is obvious, that is, the child has cough and congestion to suggest a cold, or a red, swollen patch of skin to suggest a bacterial soft-tissue infection.  In some cases, fever may be the only sign of an impending serious or life-threatening condition.  Fever is a symptom of disease and by itself, is rarely dangerous unless it is extremely high (more than 104-106 degrees for example).   It is the parent's and pediatrician's job to determine when fever should be evaluated with expensive and invasive tests such as blood draws, spinal taps, or imaging studies.  Fever can be controlled with medicines call antipyretics (i.e., ibuprophen, acetaminophen), and lowering an elevated body temperature often makes the child feel dramatically better.

What is fever?

Body temperature varies slightly throughout the day and from person-to-person.  Several studies have been performed to evaluate the "normal" body temperature of humans.  Thousands of children and adults had their body temperature measured multiple times and averages were determined.  The most commonly accepted value for a "fever" is 38 degrees Celsius (100.4 degrees Farenheit) or above.

What causes fever?

Chemicals called "pyrogens" are released into the body during a disease process.  These pyrogens can be toxins released by bacteria or parts of germs that are processed by the immune system.  Activated immune cells release chemicals that also act as pyrogens.  These pyrogens notify the brain to "reset" the body's thermostat in a part of the brain called the hypthalamus.  The hypothalamus instructs the body to conserve more heat by constricting blood vessels, causing shivering, or causing the body to feel "cold" so you put on more clothing.

What is the best way to determine body temperature?

The most accurate means to determine body temperature is with a rectal thermometer.  Oral thermometers are also accurate but may underestimate temperature when not placed under the tongue or not left in place for an appropriate amount of time (this depends on the type of thermometer).  Thermometers placed in the ear or under the arm are less accurate.   Feeling the child's skin (i.e., forehead) is a reasonably good means of determining the presence of high body temperature (described as a subjective fever).

Is fever bad?

No.  By itself, fever is actually helpful for fighting infection.  A higher body temperature destroys some types of bacteria and reduces replication of many germ types.  Heat increases the activity of the immune system and enhances production of germ-fighting chemicals.

Can fever cause a seizure?

Yes, high fever that develops quickly can prompt a seizure (i.e., a febrile seizure) in young children.  All seizures should be evaluated by a physician.  Fortunately, febrile seizures are rarely harmful to the child, especially if they don't cause breathing difficulty and don't last more than 5 to 15 minutes.  Brain damage is extremely rare.  Most febrile seizures occur at the onset of fever, often before the family realizes the fever is present.  Febrile seizures become much less common after the fever has been present for more than a few hours.

How is fever evaluated?

The most important goal of evaluating fever is to determine the source.  Young children may not be able to point to a source of pain or describe how ill they feel.  Because some severe infections in infants can present with just fever, a thorough evaluation may be necessary.  The decision to further evaluate fever without a known source depends on the age of the patient and the apearance of the child. 

From newborn to age 1 month - All infants in this age group with an established fever should have a full evaluation including:

• blood culture
• urinalysis
• urine culture
• spinal fluid culture and microscopic evaluation
• complete blood count

and sometimes...

• chest x-rays
• stool studies
• HSV studies (herpes simplex virus)
• other tests

All these infants should be admitted to the hospital and should receive intravenous antibiotics until the source of fever is identified or the child improves.

Ages 1 month and older - Your physician may decide to do some or all of the above evaluation.  The younger the child and the higher the concern for serious illness should prompt a more thorough evaluation.

How is fever treated?

Fever can be treated with antipyretics (i.e., ibuprophen and acetaminophen).  Parents should not feel like they have to "fight the fever."  Fever helps the body fight infection.  The main reason to treat fever is to make the child feel better.  A child that feels better is more likely to drink adequate fluids to prevent dehydration and to eat better.

Should I cool my child down with ice or cold water?

This is not necessary for fever caused by an infection.  A physician may recommend cooling the body rapidly with ice or cool water when the elevated body temperature is caused by the environment (i.e., heat stroke or heat exhaustion).