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Everything You Need to Know About Fever

Even though I've seen my three kids through everything from the flu to the chicken pox, I almost lost it the night my toddler spiked a fever of 104°F. Why was she burning up? Should I rush her to the emergency room or wait for her doctor to return my call? Fortunately, he phoned back within 30 minutes, and all it took to reduce Rosalie's fever was some infant Tylenol and a lukewarm bath. Before long she fully recovered from what proved to be a harmless virus.

There's no doubt about it: Fevers are scary. Indeed, fevers account for nearly 30 percent of visits to the pediatrician. But in most cases a high temperature won't harm your child unless it hits 105°F  --which is very rare.

"Fever is not an illness but a sign that the immune system is fighting off an infection," says Lynn Smitherman, M.D., assistant professor of pediatrics at Wayne State University in Detroit. "When viruses or bacteria attack the body, white blood cells come to the rescue by producing interleukin, a hormone that raises body temperature. In effect, this rise in body heat helps kill the germs that are making your child sick." There's also some evidence that a fever helps fight illness by lowering blood levels of iron, which actually may be needed by germs in order for them to survive.

Normal highs and lows

A high temperature doesn't necessarily mean that a child is sicker than if he has a low one. "How he acts is a more accurate indicator of how ill he might be," says Anne Thiele, M.D., assistant professor of pediatrics at the University of Alabama School of Medicine, in Birmingham.

"If your baby is over four months, a little listless but isn't fussing much, and still seems interested in feeding, then a slight fever doesn't need medical attention."

In fact, in a child over 2 months of age, a temperature isn't even considered a fever until it's 100.4°F or higher. A child's normal body temperature is about 98.6°F, but it will fluctuate throughout the day, says Mark Stegelman, M.D., a pediatrician on staff with Children's Health Care of Atlanta. "A baby's temperature can be as low as ninety-seven degrees or as high as ninety-nine degrees and still be normal."

These variations are caused by a host of different factors, including the time of day, his activity level, how heavy his clothing is, or whether he's just had a warm bath. Temperature readings also depend on the type of thermometer. Most doctors consider a rectal thermometer to be the gold standard: Its readings are closest to core body temperature. Due to the different way bodies conduct heat, both ear and underarm thermometers can be off by a degree or two.

No matter which method you use, it's important to know your child's normal range so you have something to compare it with when he's sick, says Dr. Stegelman. As a reference, take his temperature just before 6 a.m., when body temperature is typically lowest, and again between 5 and 7 p.m., when it normally peaks.

When to call the doctor

The American Academy of Pediatrics' recommendations depend on the child's age and rectal temperature:

2 months or younger: 100.4°F or higher, even if he shows no other symptoms of illness. "Go to the emergency room if you have to," says Charles Shubin, M.D., director of Children's Health Center at Mercy FamilyCare, in Baltimore. "In the early weeks of life, babies have a limited ability to fight illness as their immune system isn't fully developed."

3 to 6 months: 101°F or higher.

Over 6 months: 103°F or higher.

Call your doctor if your feverish child of any age develops any other symptoms  -- such as an earache, a rash, swollen glands, or trouble breathing.

Febrile seizures can occur when a child's temperature soars too quickly. While these are frightening for you, they are rarely serious. The child may stiffen, roll up his eyes, or shake. If your child has one, lay him on the floor or a bed away from sharp objects. Never force a spoon or any object into his mouth. If the seizure lasts less than a minute, as they often do, call your doctor as soon as it's over. If the seizure lasts longer than a minute, call 911.

Temperature taking

Tell the doctor which thermometer you used, the body part you took the temperature from, and the exact reading you got. When choosing a thermometer, factor in your baby's age. (Mercury has been linked to nervous-system damage, so if you have a mercury thermometer, bring it to your pediatrician for disposal.) Here are the options:

Rectal For babies under 3 months, when even a slight fever can be serious, you'll want a rectal thermometer, which is the most accurate. Lubricate the tip with petroleum jelly. Place your baby on his back, lift his legs like you're changing his diaper, and slide the thermometer about a half inch into the rectum. The Safety 1st 8-Second Fold-Up Thermometer ($10, speeds up what can be an unpleasant task.

Temporal artery This new type of thermometer, used by many hospitals, is suitable for all ages. Just place it in the center of the forehead and sweep over to the hairline; a reading takes one second. Try Exergen's Temporal Thermometer ($30,

Underarm Armpit readings are fine for babies over 3 months, though they'll usually register a degree low. Place the thermometer tip in the center of your child's armpit and press his arm firmly against his chest. Hospital's Choice 10-Second Digital Thermometer gives underarm, rectal, or oral readings ($10,

Pacifier Binky thermometers can be a lifesaver, though on average they're half a degree low. Just place it in the baby's mouth. Lumiscope's Babytherm ($18, beeps when the reading is complete.

Ear This convenient method isn't ideal for babies under 12 months, as it can give a false high or low reading. Gently pull the upper part of your child's ear back and up. Place the probe straight into the ear canal. Then take several readings to determine if your baby has a fever. The Summer Infant Digital Ear Thermometer ($25, takes readings in one second.

Fever relievers

To help your baby feel better fast:

Offer him plenty to drink Prolonged fever can lead to dehydration, so continue with breastfeeding or formula. Your doctor may also recommend giving your child a rehydrating solution, such as Pedialyte, ReVital, or Gerber LiquiLytes.

Make him comfortable Don't try to help a child "sweat out" a fever by bundling him up; that will make it last longer. Dress him in lightweight, breathable clothes.

Consider using medication It's safe to use acetaminophen (Infant Tylenol) or ibuprofen (Infant Motrin, Infant Advil) if you get the okay  -- and the proper dosage  -- from your doctor. (Never give aspirin; it's been linked to Reye's syndrome, a disease that affects the brain and the liver.) While ibuprofen's effects can last for six to eight hours, it's not approved for use in infants under 6 months of age.
Acetaminophen lasts for only four hours, but it's gentler on the stomach and can be given to newborns. Don't alternate doses of acetaminophen and ibuprofen without talking to your pediatrician first. "It's vital you write down every dose and medicine you give," says Dr. Stegelman. "Mixing medications can be confusing and could put children at risk of an overdose."

Try a sponge bath Research suggests that a lukewarm sponge bath will help lower your baby's temperature if given 30-45 minutes after he takes fever-reducing medication. Don't put your child in cold water  -- shivering will only warm him up  -- and take him out if he appears uncomfortable. Never try to cool him down with rubbing alcohol as it can be toxic if inhaled.

Above all, relax! Most kids bounce back from a fever in a day or two. With a healthy dose of TLC, your child should be well again in no time.

Lisa Collier Cool is an award-winning health and parenting writer based in New York, and a mother of three.