Fever isn’t the only indication of illness—and on its own can be an unreliable measure of how sick a baby really is. A baby who’s running a moderately high fever but is cheerful and active is likely to be less sick than a baby who’s running a low-grade fever (or no fever at all) but is clearly out of sorts and lethargic. After taking a baby’s temperature, also take a look at other measures of well-being, including how a baby looks, is behaving, and is eating.
Temperatures are most often taken through the mouth, the rectum, the armpit (axilla), or the ear.
Since putting a thermometer in a baby’s mouth is dangerous (most doctors do not recommend taking oral temperatures until a child is four or five), you’ll go one of the other routes for now.
Before you start. Try to keep your baby calm for half an hour before temperature taking, since crying or screaming could turn a slightly elevated temperature into a high one. (Though it’s necessary to withhold hot or cold drinks or foods before taking an oral temperature, as they too could affect temperature readings, this precaution isn’t necessary when taking rectal, axillary, or tympanic temperatures.)
Choosing a thermometer. The AAP recommends that parents no longer use glass mercury thermometers because of the dangers of mercury exposure. Instead, choose from the following:
Digital thermometers. These are safe, easy to use, readily available, and relatively inexpensive.
They can be used to take a rectal, oral, or axillary (armpit) reading (but don’t use the same
thermometer for oral and rectal). With a digital thermometer, you’ll have your reading in about 20 to 60 seconds—a real advantage when you’re dealing with a squirming infant. Look for a
thermometer that has a flexible tip for extra comfort. If you want, you can use disposable covers available in drugstores, but they are not necessary.
Pacifier thermometers. Shaped like a pacifier, and designed to give an oral reading in a baby too young to use an oral thermometer, these usually read between 0.2°F and 0.5°F lower than rectal thermometers. And since they require an average of three minutes to get a reading, they are difficult to use with an uncooperative baby and therefore are not very reliable.
Tympanic thermometers. These thermometers, which measure the temperature in the ear, are fairly expensive. And even though they provide a reading in just seconds, they can be difficult to position (though some have feedback guides to make sure it’s placed properly). In general, a reading from the ear is less reliable than an axillary (armpit) one, and neither is as accurate as a rectal reading—still considered the gold standard. Ear readings may be even less accurate in
young infants, who have very narrow ear canals; most experts agree that you should hold off using an ear thermometer until your baby is at least three months old, preferably over a year. Wax in the ear can also interfere with the temperature reading, no matter what a child’s age. If you do have a tympanic thermometer, ask the doctor for a demonstration on proper use.
The rectal method.
Temporal artery thermometers. These measure temperature with a transducer that rolls across the forehead, and have been shown in studies to be very accurate (though still not as accurate as a rectal). They’re easy to use and are becoming more widely available, though they’re expensive.
Taking the temperature.
Rectal: Prepare the thermometer by lubricating the sensor tip with Vaseline and bare baby’s bottom, speaking reassuringly as you do. Then turn baby onto his or her tummy on your lap (which allows the legs to hang down, making insertion easier) or on a bed or changing table (where a small pillow or folded towel under the hips will raise the baby’s bottom slightly for easier
insertion). To distract baby, try singing a couple of favorite songs, or putting a favorite book or toy in baby’s line of vision. Spread the buttocks with one hand, exposing the anus (the rectal opening).
With the other, slip about an inch of the tip of the thermometer into the rectum, being careful not to force it. Hold the thermometer in place until it beeps, using your other fingers to press the buttocks together to keep the thermometer from sliding out and to keep baby from wriggling. Remove the thermometer immediately, however, if baby begins to show very active resistance.
Axillary, or underarm: An axillary reading is useful when a baby has diarrhea or won’t lie still for a rectal or if only an oral thermometer (which should never be used rectally) is available. You can use a digital rectal or oral thermometer for an underarm reading. Remove baby’s shirt so it won’t come between the thermometer and baby’s skin, and be sure the armpit is dry. Place the tip of the thermometer well up into the armpit and hold the arm snugly over it, gently pressing the elbow against baby’s side. Distract baby as needed.
Tympanic: Use one that uses feedback to guide you to the proper position or ask the doctor for a demonstration.
Reading the thermometer. A rectal temperature is the most accurate since it picks up temperatures
from the body’s core. Temperatures obtained rectally, as they are most frequently in infants, are usually one-half to a full degree higher than those determined orally; axillary readings are about one degree lower than an oral temperature. The norm for an oral reading is 98.6°F; the norm rectally is 99.6°; and 97.6° is normal for an axillary reading. A fever of 102.2° taken rectally is roughly equivalent to 101.2° taken orally and 100.2° by an armpit reading.
The underarm method.
Storing the thermometer. After use, wash the thermometer with cold soapy water, rinse, and swab the sensor tip with alcohol. Be careful not to wet the digital display, on/off button, or battery cover.
EVALUATING A FEVER
Behavior is a better gauge of how sick an infant is than body temperature. A baby can be seriously ill, with pneumonia or meningitis for example, and have no fever at all, or have a high fever with a mild cold.
Under the following circumstances a baby with a fever requires immediate medical attention (call the doctor even in the middle of the night, or go to the emergency room if the doctor can’t be reached):
The baby is under two months old with a fever of over 100.2°F rectally.
A baby over two months has a fever over 105°F rectally.
The baby has a convulsion for the first time (the body stiffens, eyes roll, limbs flail).
The baby is crying inconsolably (and it clearly isn’t colic), cries as if in pain when touched or moved, or is whimpering, nonresponsive, or limp.
The baby has purple spots anywhere on the skin.
The baby is having difficulty breathing once you’ve cleared the nasal passages.
The baby’s neck seems stiff; baby resists having the head pulled forward toward the chest.
The onset of fever follows a period of exposure to an external heat source, such as the sun on a hot
day or the closed interior of an auto in hot weather. Heatstroke is a possibility (see page 582), and immediate emergency medical attention is indicated.
A sudden increase in temperature occurs in a baby with a moderate fever who has been overdressed or bundled in blankets. This should be treated as heat illness.
The doctor has instructed you to call immediately should your baby run a fever.
You feel something’s very wrong, but you just don’t know what.
Under the following conditions a baby with fever needs medical attention as soon as practical: