Taking a rectal (in the bottom) temperature is the most accurate way of measuring your child's temperature. However, you may find this hard to do, especially with an older toddler or child. Taking an armpit temperature can also be used for children it isn't as reliable as a rectal temperature but can give you an idea about whether or not your child has a fever. If your child is over 5 years old, taking an oral temperature is a reliable method. Be sure your child is able to keep her or his mouth closed and tongue held down for about 3 minutes to get a good reading.
Ear thermometers are not commonly used because they are more expensive and are less accurate than rectal measurements, but they can be used for children older than 2 years of age when a rectal temperature is not practical or possible. Devices (sensors and strips) that check the temporal (forehead) temperature are not recommended, as they do not give reliable measurements.