Wei Qi, as mentioned earlier in this book, corresponds to the immune system.
In Traditional Chinese Medicine, Wei Qi acts as a protective barrier that begins under the skin and extends outward, forming a defensive shield.
Pathogenic factors such as viruses, bacteria, and climatic influences like cold, wind, and dampness are prevented from entering the body by this system.
When a pathogenic factor attacks, the body increases its internal heat as part of the defense process.
This occurs because Wei Qi is Yang in nature — warm and active — and the body mobilizes more of it to respond to the threat.