Rectal temperatures are more accurate so they might also be used in someone who has severe hypo- or hyperthermia to obtain a more accurate core temperature. ... If someone has a heart condition, inserting a rectal thermometer can stimulate the vagus nerve and cause heart arrythmias (irregular heart beats).
All human beings are 99.9 percent identical in their genetic makeup. Differences in the remaining 0.1 percent hold important clues about the causes of diseases.