The differentiation between exterior and interior syndromes is not only a marker for the location and depth of diseases such as typhoid and warm diseases, but also indicates the location and depth of internal injuries and the transformation of disease severity. Therefore, Zhang Zhongjing elaborated extensively on the manifestations of exterior and interior syndromes in his works “Shang Han Lun” and “Jin Kui Yao Lue,” and provided detailed methods for their application. Later generations of physicians established this as one of the general principles for differentiating internal injuries and external pathogenic factors.
So how do we determine the location of the disease as exterior or interior and apply this concept in treatment? I believe:
1. The methods for differentiating exterior and interior syndromes mainly include three approaches:
1. The symptom-based method: Regardless of whether it is an external pathogenic factor or an internal injury, as long as the disease is located in the skin and hair, the Taiyang meridian, or the Lung meridian, and exhibits symptoms associated with these locations, it is termed an exterior syndrome. For example, the symptoms described in “Shang Han Lun” as “Taiyang disease… with stiffness and pain in the head and neck, and aversion to cold” and the “wind-heat syndrome” described by Chen Pingbo as “body heat, aversion to wind, headache, and cough”. Conversely, if the disease is deep-seated, affecting Qi and blood, internal organs, or bone marrow, it is termed an interior syndrome. As Zhang Jiebin stated in “Jing Yue Quan Shu”: “Interior syndromes are those diseases located within the internal organs. Any disease arising from within may be due to emotional disturbances, overexertion, dietary harm, or indulgence in wine and lust, all of which are classified as interior syndromes.” If a condition starts as an exterior syndrome and later manifests internally with symptoms in the internal organs, it is termed a transition from exterior to interior syndrome. “Shang Han Lun” states: “Initially, in Taiyang, when the disease first occurs, sweating is induced, but if the sweat does not fully emerge, it then transitions to Yangming.” If a condition starts as an interior syndrome and later presents with exterior symptoms, it is termed a transition from interior to exterior. “Wen Yi Lun” states: “After an interior syndrome, the pulse becomes floating and slightly rapid, with slight fever and mental confusion; this indicates that the pathogenic heat is floating on the skin surface.” Generally speaking, a transition from exterior to interior indicates a worsening of the condition, while a transition from interior to exterior indicates an improvement.
2. The pulse diagnosis method: Regardless of whether it is an external pathogenic factor or an internal injury, if the pulse is floating, it is termed an exterior syndrome; if the pulse is deep, it is termed an interior syndrome.
As stated in “Shang Han Lun”: “In Taiyang disease, the pulse is floating.” In “Wai Gan Wen Bing Pian”: “Wind-heat syndrome… pulse is floating and rapid… indicating the pathogen is in the exterior.” In “Bin Hu Mai Xue”: “A deep pulse indicates an interior condition.” In “Yi Xue Xin Wu”: “For any disease, if the pulse is floating, it indicates an exterior condition… if the pulse is deep, it indicates an interior condition.”
3. The tongue diagnosis method: Generally, exterior syndromes do not cause changes in tongue quality. If the color of the tongue changes, it indicates disease in the five internal organs, while the thickness of the tongue coating often indicates whether the condition is in the exterior or interior, or whether it has transitioned from exterior to interior or vice versa.
As pointed out by Mr. Deng Tietao in “Traditional Chinese Medicine Diagnosis”: “In fact, whether it is an external pathogenic factor or an internal injury, observing the thickness of the coating is sufficient to understand the depth and severity of the pathogenic Qi. A thin coating often indicates the initial stage of disease, with the pathogenic Qi still shallow and the disease located in the exterior; a thick coating indicates that the pathogenic Qi has penetrated into the interior, with the disease being deeper and the pathogenic Qi being heavier; a crimson tongue indicates heat entering the Ying and blood, with the disease being even deeper and more severe.”
2. Treatment methods for exterior and interior syndromes
The treatment principle for exterior and interior syndromes can be summarized in one sentence: that is, for exterior conditions, one should release the exterior, and for interior conditions, one should treat the interior. In other words, regardless of whether it is an external pathogenic factor or an internal injury, if the disease is in the exterior, one should use methods to release the exterior; if the disease is in the interior, one should use methods to treat the interior. As stated in “Su Wen: Yin Yang Ying Xiang Da Lun”: “If it is in the skin, induce sweating to release it.” This means that whether it is an external pathogenic disease such as typhoid or warm disease, or internal, surgical, gynecological, pediatric, ophthalmological, otolaryngological, or dermatological conditions, as long as the pathogenic Qi is in the exterior, one can use herbs such as Ma Huang (Ephedra), Gui Zhi (Cinnamon Twig), Zi Su (Perilla), Sheng Jiang (Fresh Ginger), Jing Jie (Schizonepeta), Fang Feng (Siler), Qiang Huo (Notopterygium), Bai Zhi (Angelica Dahurica), Gao Ben (Ligusticum), Cang Er Zi (Xanthium), Cong Bai (Scallion), Bo He (Mint), Niu Bang Zi (Burdock Seed), Chan Tui (Cicada Slough), Sang Ye (Mulberry Leaf), Ju Hua (Chrysanthemum), Ge Gen (Kudzu Root), Sheng Ma (Cimicifuga), Fu Ping (Duckweed), Xi Xin (Asarum), and formulas such as Ma Huang Tang (Ephedra Decoction), Ge Gen Tang (Kudzu Decoction), Gui Zhi Tang (Cinnamon Twig Decoction), Da Qing Long Tang (Major Blue Dragon Decoction), Jiu Wei Qiang Huo Tang (Nine Flavor Notopterygium Decoction), Xiang Ru Yin (Aromatic Madder Drink), Sang Ju Yin (Mulberry Leaf and Chrysanthemum Drink), Yin Qiao San (Honeysuckle and Forsythia Powder), Bai Du San (White Toxic Powder), and Chai Ge Jie Ji Tang (Bupleurum and Ge Gen Decoction) for treatment. However, specific applications must pay attention to the following issues:
1. The nature of the pathogenic Qi
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If it is wind, one should use herbs to disperse wind and release the exterior, such as Fang Feng, Gui Zhi, Sang Ye, Bo He, Ju Hua, and Chan Tui;
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If it is cold, one should use herbs to disperse cold and release the exterior, such as Ma Huang, Gui Zhi, Xi Xin, Du Huo, Qiang Huo, Fang Feng, Bai Zhi, and Gao Ben;
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If it is summer heat, one should use herbs to eliminate summer heat and release the exterior, such as Xiang Ru, Huo Xiang, Pei Lan, Zi Su, and Bo He;
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If it is dampness, one should use herbs to eliminate dampness and release the exterior, such as Qiang Huo, Du Huo, Fang Feng, Bai Zhi, and Cang Zhu;
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If it is dryness, one should use herbs to moisten and release the exterior, such as Zi Su and Bo He.
2. The location of the pathogenic Qi, i.e., the meridians, upper and lower parts, skin, and muscles.
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If it is in the Taiyang meridian, use Qiang Huo and Gao Ben;
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If it is in the Yangming meridian, use Sheng Ma, Bai Zhi, and Ge Gen;
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If it is in the Shaoyang meridian, use Chuan Xiong, Chai Hu, and Bo He;
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If it is in the skin, use Fu Ping;
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If it is in the muscles, use Ge Gen and Sheng Ma;
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If it is in the upper part, use Qiang Huo, Bai Zhi, Gao Ben, Man Jing Zi, and Chuan Xiong;
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If it is in the lower part, use Du Huo, etc.
3. The presence of combined or concurrent syndromes
This refers to the simultaneous presence of different pathogenic Qi, as well as the occurrence of multiple meridians being affected at the same time. This situation is referred to as combined or concurrent diseases in “Shang Han Lun.”
4. The relationship between pathogenic Qi and Zheng Qi
Here, Zheng Qi refers to both Yin and Yang, both Qi and blood, and both the five internal organs and six hollow organs. When assessing the relationship between Zheng and Xie, one must distinguish the nature of Zheng Qi and the different relationships between Zheng and Xie.
5. The proportional relationship between exterior syndromes and various factors
For example, the relationship between exterior cold and exterior dampness, the proportional relationship between Yang deficiency and exterior pathogenic Qi, etc.
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