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Taking Baby's Temperature

Thermometers have changed a lot in the last few decades. Mercury thermometers are no longer used, because mercury is a toxic metal, and digital thermometers have replaced them. Contact your local health department, waste disposal authority, or fire department for information on how to properly dispose of mercury thermometers.

For a parent who needs to take an infant's or child's temperature, there are now four digital options:

  • Rectal temperature. Various digital rectal thermometers are available for taking rectal temperatures. Parents worry about these because of fear of injury from improper insertion. At least one infant digital rectal thermometer currently available has a probe so short that there's little chance of injury. The thermometer has an audible alert when the measurement is done, as well as a digital readout.

  • Axillary (underarm) temperature. Any of the digital thermometers can be used in the armpit, but a disk-shaped thermometer fits more comfortably. The entire disk is covered when the arm is brought against the chest wall. The temperature appears on a digital readout when the alert sounds. Axillary thermometers  may be used for babies ages 3 months and older.

  • Tympanic (ear) temperature. The tympanic thermometer is the quickest of the digital thermometers, working in only a second. In order to get an accurate temperature, the thermometer must be directed toward the eardrum. Tympanic thermometers may not be accurate for newborns and require careful positioning to get an accurate reading. Parents may initially have some difficulty doing this, but with practice, it becomes an easy process.

  • Temporal artery thermometry. This thermometer is extremely easy to use, is as accurate as a rectal thermometer with less discomfort, and is less disturbing to a newborn. It measures the core body temperature through the artery of the forehead.

You should avoid other fever "detectors," such as strips that you place on a child's forehead or pacifiers that have a dot that changes color to indicate a fever. These aren't as reliable as a fever thermometer. If an infant is able to keep his mouth tightly closed around the pacifier, the temperature may be accurate, but if the infant must breathe through the mouth, the temperature will not be accurate.

When using any of the digital devices, read and carefully follow the directions. If you choose to take rectal temperatures, the digital rectal thermometer with the short probe is recommended because of reduced risk for injury.

One of the most important things to remember about fever in children is that a child's appearance—how sick he or she looks—and your gut feeling should help make the decision on whether to call your health care provider. Children can be extremely or even critically ill and not have a fever. They also can have a high fever and be only mildly ill, or even running around as if nothing were wrong. Your decision to call should be based on all this information with a few ironclad exceptions.

When to call the doctor

These are instances when you should call your health care provider about a fever in your child:

  • If a child younger than age 3 months has a rectal or tympanic temperature above 100.4 degrees F

  • If a child between age 3 months and 3 years has a rectal or tympanic temperature above 102 degrees F

  • If an older child has a high temperature

Parents should call for any fever in a child who is lethargic, looks ill or isn't responsive.

When you call the doctor, report the actual reading on the thermometer and say where the temperature was taken: the ear, the underarm or the rectum. Some parents try to adjust the reading based on what they think is "right" by mouth, which only confuses the health care provider. In addition, be prepared to tell your doctor about any other symptoms or signs that your child may have. Try to stay relaxed, listen to his or her questions and answer them as accurately as possible.

How to treat it

Acetaminophen or ibuprofen may be used to treat a fever in infants and children. Follow the package instructions carefully or the dosing instructions given to you by your health care provider. Take a second temperature reading an hour after you have given a dose of children's non-aspirin medicine. The temperature should be down and possibly close to normal. Expect it to rise again in about three to four hours, as the medicine wears off. Give a second dose after four to six hours.

After you have discussed any significant fever or symptoms with your health care provider, you may want to give your child a warm (not cold) bath for any temperature above 103 degrees F. Keep your child in the bath for at least 30-45 minutes to allow the fever to dissipate.

While your child has a fever, you should avoid over-bundling him. A T-shirt or light blanket is fine as long as the child does not have chills.