# Eli5 Why you shouldn’t measure your body temperature on an ear where you layed down when you got fever? Where do the extra degrees come from?

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Eli5 Why you shouldn’t measure your body temperature on an ear where you layed down when you got fever? Where do the extra degrees come from?

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The surface of your body can have another temperature than the inner part because it is in contact with the surrounding air. Oral, ear, armpit, rectal, skin etc all have slightly different temperatures even if you measure them at the same time. You need to compensate for the difference to get the core temperature.

Are you asking about the problems of measuring in an ear that was toward the pillow when lying down on the side?

The pillow will work like insulation that rescues air flow and heat transportation. So your ear toward the pillow will be slightly warmer than the other ear for this reason. So if you first measure the temperature before you lay down and then after it can the reading can increase even if the core body temperature has stayed the same, the ear got a bit warmer

I’ll take a shot. Measuring an ear that was laying on the pillow doesn’t measure any “extra” heat, but it still will be inaccurate. The manufacturer of the thermometer has calibrated its readouts based on measurements taken from an ear that was out in the open. Ear temperatures of a person will always be a little cooler than oral or rectal temperatures, so the manufacturer has to take that it account.

For example, through lots of study, they’ll determine that if the ear thermometer measures 102 degrees, it corresponds to a real (taken rectally) body temperature of 104 degrees. The difference is the result of cooling that happens because the ear is out in the open. They’ll calibrate the thermometer to show 104 when it reads 102.

If you measure an ear that was insulated by the pillow, it is losing less heat to the air, so it might be closer to that real temperature of 104 degrees. When the thermometer then “corrects” the temperature, it will show up at 106.