What exactly is fever?

You know what's coming. You've traded your flip-flops for rain boots, your tank tops for sweaters and your carefree summer attitude has floated off like a lost helium balloon.

Soon you'll be trying to muster some holiday spirit as you fret about the heating bills and wonder whether you'll be sucker-punched by a nasty virus. It could be a cold, it could be the flu; either way, it's likely to announce itself with a fever, your body's way of combating inflammation or infection.

The traditional standard for body temperature of a healthy adult is 37.0 degrees Celsius or 98.6 degrees Fahrenheit. This number was arrived at in 1861 by a German physician named Carl Wunderlich, who sampled and averaged the temperatures of a large population of healthy individuals.

The fact that we all learned Wunderlich's number in school doesn't make it right, however.

A 1992 study published in the Journal of the American Medical Association gives 98.2 F as the average human temperature. Normal can be any temperature within 0.7 degrees of that, according to research done at the University of Maryland.

This makes the acceptable "healthy" range of oral temperature anywhere between 97.5 and 98.9. You can move within that range during the day.

"Temperature variation is, to a point, normal," says Dr. Timothy Little, an internal-medicine specialist who practices in Edmonds. "Body temperature varies with physical activity, ovulation, hormonal status and many other things."

You have a fever when your temperature exceeds your normal range.

A fever without other symptoms that lasts three to four days, comes and goes, and gradually declines over time is usually not a cause for concern.

"Fevers are not always bad and are often beneficial," said Dr. Louis Ramos, a Team Health hospitalist in Edmonds. "Fevers are natural mechanisms that enhance the body's immune system in fighting off bacterial and viral infections. In some cases, fevers actually impair the growth of bacteria and inhibit viral replication, giving the immune system better odds at fighting off infection."

So fevers are good, right?

Not exactly. While most healthy adults and children can tolerate fevers for a short time without problems, it is important to look at the other symptoms of illness. If a fever goes above 104 degrees — a situation doctors call hyperpyrexia — then it may cause significant tissue damage and would most certainly be harmful.

Prolonged high temperatures can cause many problems, including seizures in some people. Older adults, younger children and especially babies may not have immune systems strong enough to fight an infection and may need more advanced medical treatment.

Fever can be classed as:

• Low grade (100.4-102.2 degrees)

• Moderate (102.2-104 degrees)

• High grade (above 104 degrees)

Almost all infectious diseases can cause fever, and most fevers are caused by infections, however tissue inflammation can also cause low-grade fevers. The higher temperature speeds up the body's chemical reactions and may help it repair tissue faster.

When to call a doctor

First of all, it is important to consult with a physician if there's ever a question about whether a fever might be dangerous.

If the situation doesn't seem dire, most doctors would say to call when:

A baby less than 90 days old has a temperature of 100.2 degrees or higher.

A baby 3 to 6 months old has a fever of 101 or higher.

A baby 6 to 12 months old has a fever of 103 or higher.

A child younger than 2 has a fever that lasts longer than 24 to 48 hours.

Anyone has a fever over 104 unless it comes down readily with treatment, and the person is comfortable.

Other worrisome symptoms are present, for example, confusion, difficulty breathing, stiff neck, inability to move an arm or leg or a first-time seizure.

"Lethargy is particularly worrisome in children with fevers because it can signify a serious infection," says Dr. Michelle L. Gordon, a Team Health hospitalist in Edmonds. "Call your physician when a fever is accompanied by significant behavior changes."

Not all doctors do things the same way; your doctor may have her own set of guidelines about when a fever requires her attention, and you should use those.

Fever treatment at home

Fevers are uncomfortable, of course. But they can frequently be treated effectively at home, according to Diane Kirse, a registered nurse who has practiced in the healthcare field for 30 years,

"So many times parents rush to the ER [emergency room] without trying measures to bring the fever down, such as cooling techniques or medication. Some people don't administer medication such as Tylenol or Ibuprofen appropriately. They fail to administer the correct dose and don't repeat the dose often enough."

If a fever is being treated at home, there are several ways to help lower the temperature and provide comfort:

Do not bundle up someone who has chills, because this raises the body temperature even higher.

Do remove excess clothing or blankets. The environment should be comfortably cool. For example, one layer of lightweight clothing and one lightweight blanket to sleep. If the room is hot or stuffy, a fan may help.

A lukewarm bath or sponge bath may help cool someone with a fever. This is especially effective after medication is given, otherwise the temperature might bounce right back up.

Do not use cold baths or alcohol rubs . These cool the skin, but often make the situation worse by causing shivering, which raises the core body temperature.

Offer cool liquids, as tolerated.

Offer over-the-counter medicines such as acetaminophen (the active ingredient in Tylenol), ibuprofen (the active ingredient in Advil), or other fever formulas. Always use medications according to the directions on the label. Always check with your physician before giving any over-the-counter medications to children younger than a year.

No one likes a fever, but knowing what it is, how to treat it and when to call for help will help you chill out when a fever strikes.

Anna Hiatt is a registered nurse living in Brier.