When pathogenic qi breaks through the surface and enters the body, it can cause internal injuries. In the Shang Han Lun (Treatise on Cold Damage), apart from the surface symptoms treated by Gui Zhi Tang (Cinnamon Twig Decoction) and Ma Huang Tang (Ephedra Decoction), conditions affecting the body from the skin to the bone marrow, as well as the five zang organs and six fu organs, generally fall under the category of internal injuries.
Internal injuries can result from external pathogenic factors penetrating the immune system (Wei Qi) and deeply affecting the interior, or from inhaling polluted and toxic air through the mouth and nose. They can also arise from consuming substances that the body cannot digest or absorb, leading to food stagnation or metabolic disorders. Diseases entering from the outside can either penetrate through the skin or the mouth, causing internal damage and resulting in internal injuries.
Additionally, irregular daily activities, excessive physical exertion, and unregulated sexual activity can lead to weakness due to overconsumption, which is akin to what Western medicine refers to as sub-health states or neuroses. This also falls within the scope of internal injuries. This type of internal injury is primarily self-inflicted, despite the influence of external factors, and is unrelated to external pathogenic invasion.
Excluding diseases caused by external factors such as colds from climatic changes and various external injuries or emotional disorders, the majority of diseases are classified as internal injuries. For instance, Western medicine categorizes cardiovascular diseases, heart diseases, various organ inflammations, hyperplasia, deformities, and even tumors based on location, as well as conditions like hypertension, diabetes, and various neural pains based on symptoms. Systematically, this includes immune system diseases, neurological disorders, connective tissue diseases, and blood disorders, or various complex diseases named after their discoverers or regions of occurrence. In Traditional Chinese Medicine, symptoms are named as headaches, coughs, vomiting, abdominal pain, hemorrhoids, hernias, etc. The list can be extensive, and the causes are virtually limitless. However, they ultimately boil down to imbalances of yin and yang, water and fire, dryness and dampness, temperature drops, increased humidity, stagnant wind, and obstructed water flow, leading to conditions ranging from distension and pain to accumulation and stagnation.
To treat internal injuries, one must first cultivate a calm spirit, followed by harmonizing diet, lifestyle, and medications to balance yin and yang and regulate water and fire. Once yin and yang are in harmony, the injuries can naturally heal. If the spirit is restless and thoughts are scattered, even with medication, there will be no effective governance or support, leading to futile attacks and losses, making treatment less effective than not treating at all.