Dr. Sun also notes that, though the ancients lacked the word "immune," they did have the concept of "rectifying the root and eliminating the bad." Rectifying the root means, in modern terms, increasing immunity, while eliminating the bad means removing toxins from the body, thus preempting illness.
孫安迪也指出，古人雖然沒有「免疫」這個字眼，但是「扶正祛邪」的觀念中，「扶正」就是增加免疫力，「祛邪」則是排除體內毒素，除去會使人發病的自由基。