Yin Deficiency Heat

Generally that is just the most common areas, people can technically have yin deficiency and have heat throughout their body. Generally it will range based on the degree of the underlying deficiency and what other patterns they hold (i.e. there is often more than one thing happening).

Yin deficiency is in many ways what we term “tired and wired” in the west - so you are deficient, ultimately, but then functionally locked into an adrenal/stress state which generates heat and anxiety in many cases. Part of the stress response that the body is locked in is part of the hands and feet (for example, sweaty palms and feet with anxiety).

The malar flush is a pretty strait forward explanation: yang (heat) rises and the chest and head are at the top. The hands and feet are furthest away from the interior they are more likely to be affected by a disruption of the flow of the blood and/or qi. Also the limbs are further down the line of importance than the internal organs so when circulation is weakened the body will naturally protect the interior first. Look at what happens during hypothermia for example. Hope that helps.

Just to clarify yin deficiency, like almost everything else actually, has a scale to it. A very mild yin deficiency may produce no symptoms at all whereas a very severe yin deficiency can lead to extreme sensations of heat such as steaming bone syndrome. The level of yang is not necessarily related - so you can have mild to severe yin deficiency with the same level of yang in both cases.