“Does she have a fever?” That is one of the first questions you'll be asked whenever you call your doctor with a question about a sick baby — and it will soon be one of the first questions you'll ask yourself.

Fevers do have a purpose, although their exact role is unclear. They may increase the number of white blood cells (which kill viruses and destroy bacteria) or raise the amount of interferon, an antiviral substance, in the blood and thus hinder bacteria and viruses from multiplying. Fevers aren't dangerous in themselves (although they serve as a warning of other problems), except when they rise very quickly or reach extremely high levels — above 106°F.

You will notice that your baby's fever will climb in the afternoon from a morning low. This is normal, and doesn't mean your baby is getting sicker.

Thermometers

Thermometers come in different styles: glass; digital; and tympanic. Avoid using a mercury-filled glass thermometer because of concerns about mercury. The American Medical Association issued a statement that non-mercury fever thermometers are just as effective, as well as safer than mercury-filled ones. Disposable strips aren't accurate enough for a baby under a year, and definitely not for newborns. You can take a baby's temperature rectally, under her arm (axillary), or by reading the heat off of her eardrum (tympanic). You can't, however, take his temperature orally; holding the thermometer under his tongue would be uncomfortable and he might gag or choke. Also, your baby might bite off the end.

Taking Your Baby's Temperature

For babies under three months, most doctors want you take a rectal temperature. It's the most accurate and, at this age, every degree is significant because treatment of a fever will be based on temperature.

If you are using a non-mercury glass thermometer to take your baby's temperature rectally, make sure you have one intended for rectal use. If you are using a digital thermometer, designate one for that purpose by marking it with an indelible “R.” First clean the thermometer by wiping it with rubbing alcohol or washing it with soapy water. Then make sure it is reset by shaking the thermometer until the temperature gauge reads below 98.6°F. To reset a digital thermometer, turn it off and then on again.

Put a dab of petroleum jelly on the tip of the thermometer. Lay your baby stomach down on the changing table and hold her with one hand placed firmly on her back; add another dab of petroleum jelly at the opening of her anus. Insert the thermometer tip a half inch into her rectum (never forcing it), and hold it there between your second and third fingers, with your hand cupped over her buttocks. Wait two minutes for a glass thermometer, or until a digital thermometer beeps. A rectal temperature of 100.4°F and up in a baby under three months is considered a fever.

For older babies, open up or remove her clothing to take a temperature under her arm. Put her in a comfortable position, lying in your arm or against your chest. Put the glass or digital thermometer in her dry armpit and tuck her elbow against her body. Cuddle her, making sure she doesn't move her arm. (You can pace the floor with her, just keep her arm firmly over the thermometer.) Wait four minutes, or until the digital thermometer beeps its all-done signal. An axillary temperature of over 102.2°F is considered a fever.

How to Treat a Fever

If your baby has a fever, make sure she isn't dressed too warmly and that her room isn't hot. You can strip her down to her T-shirt, but keep a light blanket handy for when her temperature begins to drop.

With your doctor's permission and confirmation of the dosage, give her a fever-reducing medicine, like acetaminophen (Tylenol) or ibuprofen (Motrin). You should see the fever start to come down thirty minutes later, sometimes sooner. If it doesn't, or spikes back up again quickly, these medicines can be alternated. While doses of Tylenol are meant to be given four hours apart and Motrin six hours apart, pediatricians sometimes recommend giving a dose of Motrin only two hours after giving Tylenol. Just don't give a second dose of the same medicine any sooner than prescribed. Talk to your doctor about what she thinks is most effective in treating fevers.

You can also try to bring your baby's fever down by giving her a bath in a few inches of lukewarm water, using a washcloth to spread water over her, and letting her air-dry. Give your feverish baby lots to drink — she's sweating out fluids, and dehydration can make her feel worse.

Febrile Convulsions

You should, however, be aggressive in fighting fevers in children who are susceptible to febrile convulsions. Two to four percent of children, most between six months and six years old, are susceptible to these kinds of seizures, characterized by symmetrical rhythmic convulsions, eyes rolling back in the head, and a loss of consciousness. Convulsions can last as long as ten minutes, but usually disappear in less than two minutes. Although it's less common, some susceptible children experience them every time they get a fever. The seizures usually have no permanent effects and are not a form of epilepsy. A seizure is likely related to fever if:

• The seizure occurs within twenty-four hours of starting a fever

• The seizure lasts less than five minutes

• The seizure affects the whole body and is not confined to one side

While your child is having a seizure, you want to focus on her care — you can call the doctor once the seizure is over. If your child has a seizure:

• Turn her on her side

• Remove any hard objects she might slam into

• Look at your watch

You need to time the seizure — your doctor will want to know its duration. If the seizure lasts longer than five minutes, call your physician or local paramedics. After five minutes the child should get emergency care and be evaluated; but seizures of that duration are rare. If your child is prone to these seizures, you will probably want to administer fever-reducing medicine sooner, rather than later. Call your doctor after the seizure is over and review the incident.