To take a child's temperature, remove upper body clothing and position the thermometer under the armpit while making sure that it only comes in contact with skin, KidsHealth advises. Fold the child's arm across her chest to prevent the thermometer from falling out of place. Wait for the thermometer to signal that the measurement is complete, and record the child's temperature. Refrain from using glass mercury thermometers, and avoid taking the temperature immediately after a child has bathed.
A temperature taken under the armpit is known as an axillary temperature, and it is slightly less accurate than oral or rectal methods, according to KidsHealth. An axillary temperature of 99 degrees Fahrenheit or above is considered a fever, compared to oral and rectal temperatures of 99.5 and 100.4 degrees Fahrenheit, respectively. Doctors typically recommend taking a rectal temperature for children under 6 months old and a rectal, ear, axillary or temporal artery reading for children between 6 months and 4 years old. Almost any method is safe for older children, including oral, but your child may prefer an axillary temperature if he has difficulty breathing and cannot keep the thermometer in his mouth.
Keep in mind that a high temperature isn't automatically cause for concern if the fever doesn't persist and your child has no serious symptoms, WebMD notes. Make sure the child consumes extra fluids, and use lukewarm water to sponge bathe your child. Avoid using cold baths or ice to lower a fever, and consult a doctor if your child develops symptoms such as diarrhea, vomiting, rash, headaches or seizures.