When we describe an object as hot, we are really comparing it with something else. The word does not mean anything by itself. We can say that we feel hot after exercise, that a cup of coffee is hot and that the surface of the Sun is hot, but we mean something quite different each time. An object can be hot compared with an ice cube but cold compared with boiling water. In fact, both the ice cube and the boiling water contain heat energy, but their temperatures are quite different. Temperature is a measure of how hot something is compared with an agreed scale. A small object with a temperature of 100°C may not have as much heat energy as a very large object with a temperature of 0°C.
I have often noted that when patients are running a fever with an infection, their face may be flushed and hot to the touch while their hands and feet may be cold and clammy. I think that the flushed face sensation causes one to feel hot when ill. And I think the cold hands and feet cause one to feel cold when ill. These can happen at the same time, and is truly miserable. Even though the body has a fever, the extremities (hands and feet) can be cool because of substances like adrenaline being pumped into circulation by the body in response to physiological insult (infection).
When running a fever, a person will often start getting dehydrated because of a lot of water loss (sweat, faster breathing). Adrenaline will increase a person’s blood pressure and heart rate. This is usually experienced as a flushed face. One of adrenaline’s functions is to constrict the blood vessels so as to raise the blood pressure. If the body is running dehydrated, this vessel constriction in the smaller vessels (the like in the hands and feet) may prevent good blood circulation in those parts of the body. Thus, the extremities can get feel cool to the touch because there is actually decreased blood flow there.
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