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How to lower a baby's fever
Take your baby's temperature rectally.
If you think your baby is running a fever, use a rectal thermometer to get the most accurate results. Place your baby on his or her stomach, or on his or her back with legs pulled up.
Coat the base of the thermometer with petroleum jelly, and insert it slowly into the anus-only about half an inch, so that the metal part is inside. Hold the thermometer still, and, when it beeps, remove it and read the results.