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Fever – How to Take a Temperature

While you often can tell if your child is warmer than usual by feeling his forehead, only a thermometer can tell if he really has a fever. There are several types of thermometers and methods for taking your child’s temperature.

Mercury thermometers should not be used. The American Academy of Pediatrics (AAP) encourages parents to remove mercury thermometers from their homes to prevent accidental exposure to this toxin.


If your child is younger than 3 years of age, taking his temperature with a rectal digital thermometer provides the best reading.

  1. Clean the end of the thermometer with rubbing alcohol or soap and water. Rinse it with cool water. Do not rinse with hot water.
  2. Put a small amount of lubricant, such as petroleum jelly, on the end.
  3. Place your child belly down across your lap or on a firm surface. Hold him by placing your palm against his lower back, just above his bottom.
  4. With the other hand, turn on the thermometer switch and insert the thermometer 0.5″ to 1″ into the anal opening. Hold the thermometer in place loosely with two fingers, keeping your hand cupped around your child’s bottom. Do not insert the thermometer too far.
  5. Hold in place for about one minute, until you hear the “beep.” Remove the thermometer to check the digital reading.


Once your child is 4 or 5 years of age, you may prefer taking his temperature by mouth with an oral digital thermometer. Clean the thermometer with lukewarm soapy water or rubbing alcohol. Rinse with cool water. Turn on the switch and place the sensor under his tongue toward the back of his mouth. Hold in place for about one minute, until you hear the “beep.” Check the digital reading. For a correct reading, wait at least 15 minutes after your child has had a hot or cold drink before putting the thermometer in his mouth.

Ear Tympanic thermometers, which measure temperature inside the ear, are another option for older babies and children. Gently put the end of the thermometer in the ear canal. Press the start button. You will get a digital reading of your child’s temperature within seconds. While it provides quick results, this thermometer needs to be placed correctly in your child’s ear to be accurate. Too much earwax may cause the reading to be incorrect. Underarm (Axillary) Although not as accurate, if your child is older than 3 months of age, you can take his underarm temperature to see if he has a fever. Place the sensor end of either an oral or rectal digital thermometer in your child’s armpit. Hold his arm tightly against his chest for about one minute, until you hear the “beep.” Check the digital reading.


Forehead scanners are new on the scene for measuring a child’s temperature. There are two types of forehead thermometers, one in the form of forehead strips and the other, a temporal artery thermometer. Forehead thermometers are very fast and easy to use. Needless to say, they have become quite popular. Thermometer strips are the easiest to use, as you only have to stick the strip to the forehead of the patient for a stipulated time. The strip contains liquid crystals which react with the surface of the skin. As per the temperature of the skin, the crystals change their color. The thermometer has a numbered scale which shows temperature for the displayed change in color. These thermometers can be used for babies as well as adults. However, in spite of all their advantages, they are considered highly inaccurate. Their inaccuracy, which results in misreading of temperature, can pose a threat to the health of the individual.

The second method to take the temperature on the forehead is by using the temporal artery thermometer. This thermometer uses infrared light for measuring the temperature of the temporal artery. The temporal artery thermometer is more accurate, although highly heat sensitive. As a result, slight temperature variations affect its reading. Thus, when you bring the thermometer from a cold room to a room of average temperature, you have to wait for some time before the thermometer becomes ‘normal.’ Also, the heat emitted by light sources can interfere with the reading of the thermometer.