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Like it or not, rectal thermometers are the gold standard for infants under 1 year. Ear thermometers, pacifier thermometers, forehead strips, and even underarm thermometers are simply not as accurate -- temperature readings may vary by 0.5 to 1.0 degree, and that difference matters. Fever in an infant can be a true emergency, and you want to be very precise.
Taking a rectal temp may seem awkward, but it's not difficult. Ask your pediatrician to show you how -- it's better to ask now than when you're panicked because your child's very hot and throwing up. Today's digital thermometers feature soft, flexible tips and display the results in seconds. Simply lubricate the tip with petroleum jelly or a water-soluble lubricant and insert it a half inch to an inch. (Diaper-changing position is ideal.) Hold the thermometer in place by squeezing your baby's butt cheeks together until the temperature registers.
• For babies 3 months or younger, call your physician if the temperature is over 100.4 F. or under 97.5 F.
• For babies 3 to 6 months, call the doctor if the temperature is 101 F. or higher.
• For babies older than 6 months, call the doctor if the temperature is 103 F. or higher. --Jennifer L.W. Fink
Originally published in Parents magazine, January 2008. Updated 2009
The answers from our experts are for educational purposes only. Please always refer to your child's pediatrician and mental health expert for more in-depth advice.