The Wei Qi pertains to Yang and so moves outside the vessels. The Lung is the organ responsible for regulating Defensive Qi. It functions to spread Defensive Qi throughout the body to the areas between the skin and muscles.
There are three functions of Defensive-Qi:
- Warming and nourishing the body.
- It helps to rgeulate body temperature.
- Prevents invasion of exogenous pathogens such as wind, cold, damp etc. In Western terms the Defensive Qi proects against germs, viruses and bacteria. This is the most important function of Defensive Qi.
Weakness or deficiency of Wei Qi can lead to invasion by external pathogens. This may manifest as an aversion to cold or heat, sweating or easily catching colds.