Why can't I accurately detect a high fever with my own hand?

[a1densmom]

I need to know WHY you can't tell if you have a high fever with your own hand...

I am thinking that it is because your body temp. is all equal?

 

[DaveC426913]

That's the answer I would expect, yes. I'm not sure there's a definitive answer.

 

[Idea04]

because both your head and hand are sensitive to heat and touch and the signals would just get mixed up. If you touch someone elses head the only signal going to your brain is from your hand.

 

[marcusl]

Yes, that's right. When you put your hand on someone's forehead, you are comparing their skin temperature to yours. If it's your hot hand on your own hot forehead it's tough to tell.

The method is a little complicated in any case because air cools your hand to a low temperature due to its large surface area (large relative to the hand's volume). For the record, normal forehead temp is about 35.4C (95.7F), hand around 33.3C (91.9F). As a result, even non-febrile foreheads feel warm to hands and young parents panic until they take their child's temp with a thermometer and see it's normal. Experience helps here. Some people use their lips, but they're about the same temp as hands so that's not much help. Doesn't work on your own forehead either...