Types of fever thermometersDigital thermometers have made difficult-to-read mercury thermometers (also known as stick thermometers) obsolete. Oral thermometers today usually pull triple duty as axillary (armpit) and rectal thermometers, as well. The UK now recommends that stick thermometers be used for armpit (axillary) measurements for newborns under 4 weeks and suggests using infrared forehead thermometers for any age above that. Ear and forehead infrared thermometers, both in-ear/on-forehead and contactless, are accurate enough to properly track a fever and are generally easier to use than stick thermometers. The Mayo Clinic now recommends infrared thermometers for infants 3 months and older and acknowledges recent studies (PDF) that show contactless, infrared thermometers to be reliable, including when used on newborns.