Are Forehead Thermometers Accurate on wiseGEEK:
Keep in mind, though, studies have shown that this type of forehead thermometer is not always accurate. It will, however, give you an idea whether or not the child has a fever.
The arterial heat balance method is a complex mathematical equation that computes the temperature of the surrounding air with the temperature of the arterial blood flow. The forehead thermometer has built-in software that can do this computation multiple times per second.