You can use an infrared thermometer to measure external body temperature if you want, though their accuracy isn`t as good as a medical thermometer. Most models state that they are accurate within 1 or 2 degree, which is not nearly precise as a medical thermometer. The temperature of your skin will also vary from your internal temperature, so if you are trying to determine if someone has a fever, it may be best to have the person open their mouth and point it down their throat rather than measuring the temperature of their forehead.