Olfactory diagnosis, as a key component of the four diagnostic methods, actually encompasses both listening to sounds and smelling odors. Currently, in terms of theoretical organization, clinical practice, and modern research, the study of olfactory diagnosis is relatively less compared to the detailed exploration of sounds. In clinical practice, the body odor of patients has significant reference value for the diagnosis of diseases. For example, distinguishing between stroke and typhoid fever is crucially dependent on the presence of sweat; if the physician detects a foul odor of sweat through olfactory diagnosis, it indicates that the patient has symptoms of sweating. Therefore, systematically organizing the relevant literature on olfactory diagnosis and deeply exploring its theoretical connotations is of positive significance for improving the accuracy of TCM diagnosis and enriching clinical practice.
1 The Evolution of Olfactory Diagnosis in Traditional Chinese Medicine
1.1 The Qin and Han Dynasties: Emphasis on Listening with Less Focus on Smelling
The Huangdi Neijing and Nanjing, as the culmination of pre-Qin medical wisdom, laid a solid foundation for the application of olfactory diagnosis in later generations. Although olfactory diagnosis is mentioned, the focus is more on “listening to sounds” rather than treating “smelling odors” as an independent diagnostic method. For example, the Suwen: Jin Gui Zhen Yan Lun elaborates on the relationship between the five organs and specific odors, while the Su Wen: Zhi Zhen Yao Da Lun describes that “all vomiting of sourness and violent pressure belongs to heat,” where “vomiting sourness” actually refers to vomit with a sour and rotten smell. Additionally, the Nanjing: Si Shi Jiu Nan also records the use of olfactory diagnosis to diagnose heat stroke, stating, “How to know it is caused by heat stroke? It is due to foul odor.”
1.2 The Pulse Classic Emphasizes Smelling Odors to Diagnose Diseases
The Pulse Classic compiled by Wang Shuhe during the Jin Dynasty had a profound impact on the development of TCM diagnostics. It was the first to clearly propose and highly emphasize the role of “smelling odors” in diagnosing diseases, greatly promoting the development of olfactory diagnosis. Although the Huangdi Neijing already had explanations regarding the five organs corresponding to specific odors, it had not yet treated it as an independent diagnostic method. The Pulse Classic explicitly points out the importance of smelling odors for diagnosis and illustrates its application in clinical practice through examples. Wang Shuhe recorded an instance where Bian Que judged a patient’s critical condition through the smell of the corpse, indicating the value of olfactory diagnosis in disease diagnosis. Furthermore, he advocated combining olfactory diagnosis with other diagnostic methods such as observation to gain a more comprehensive insight into the condition. For instance, for jaundice patients, by observing symptoms such as body odor, heat, irritability, and a dry, cracked tongue, one can determine the severity of heat toxicity and the failure of lung and spleen functions, thus predicting the severity of the condition.
1.3 Significant Developments in the Sui and Tang Dynasties with More Detailed Discussions
The Zhuyin Yuanyuan Lun by Chao Yuanfang during the Sui Dynasty made significant progress in olfactory diagnosis, providing detailed discussions on symptoms such as sour mouth, bad breath, and abnormal stool odors. For example, in the Zhuyin Yuanyuan Lun: Vomiting and Other Diseases, it identifies the signs of food retention through vinegar-like odors. The book suggests that belching with a vinegar smell is due to phlegm-damp stagnation in the upper jiao and spleen-stomach deficiency and cold, leading to undigested food and subsequent bloating and gas reversal. Additionally, in the Zhuyin Yuanyuan Lun: Pediatric Miscellaneous Diseases, Chao Yuanfang also judged the cold-heat properties of diseases based on the color and odor of feces, guiding medication accordingly. For instance, yellow and foul-smelling feces reflect stomach heat, suitable for treatment with Long Dan Decoction; while white and sour-smelling feces indicate that cold pathogens have not been resolved, requiring the use of Zhi Shuang Pill. These studies by Chao Yuanfang provided more precise evidence for TCM clinical diagnosis and treatment, promoting the development of TCM diagnostics.
1.4 Major Developments in the Ming and Qing Dynasties with New Theories on Odor Differentiation
In the field of surgery during the Ming and Qing Dynasties, when describing conditions such as abscesses and loss of vitality, not only was the patient’s voice and breath considered, but olfactory diagnosis methods were also integrated. Xue Ji mentioned in the Essentials of Surgery that “pus dissolving and swelling disappearing, with fresh water not smelling” is a good sign of wound healing, while “pus color foul-smelling indicates weak stomach qi and excessive fire” is a sign of deterioration. The Authentic Record of Surgery: Miscellaneous Sores and Toxicity provides the earliest detailed record of malignant tumors in the neck, emphasizing the identification of foul odors emitted from diseased tissues to determine poor prognosis. With the rise and development of the warm disease school, a new theoretical system centered on “differentiating odors” gradually formed, incorporating both olfactory and auditory diagnosis into the realm of olfactory diagnosis. The Plague Distinction begins with the first of the five differentiations, “differentiating odors,” to distinguish between wind-cold colds and plagues based on the presence of foul odors. The Chongqing Hall Essays also emphasizes “differentiating odors,” with author Wang Bingheng clearly stating that olfactory diagnosis should include both listening and smelling, and emphasizing the clinical value of olfactory diagnosis in non-epidemic cases. Wu Youke in the Warm Disease Treatise distinguished between typhoid dry accumulation and plague dry accumulation through the odor of feces, indicating that severe foul odors appear in the later stages of warm disease, different from general typhoid dry accumulation, and advocating for timely purging to eliminate pathogens.
1.5 The Last Two Hundred Years: Theories Refined
During the Republic of China period, many physicians began to formally incorporate olfactory diagnosis into the olfactory diagnosis system. In gynecology, physician Zhu Nanshan particularly emphasized the importance of smelling odors in the diagnosis and treatment of gynecological discharge diseases. Additionally, Liang Hanfen established a chapter on “Olfactory Method” in his Lecture Notes on Diagnosis, further clarifying the important position of olfactory diagnosis in TCM, involving the identification of pathological odors such as corpse odor, bad breath, sweat odor, fecal odor, and gas odor. The emphasis and research on olfactory diagnosis by these physicians provided valuable experience and guidance for future practitioners and contributed to the development of TCM diagnostics. Since 1949, especially with the establishment of the TCM hospital education system, the theory of olfactory diagnosis has been continuously refined. The first edition of the Textbook of TCM Diagnosis clearly divided diagnostic methods into observation, listening, inquiry, and palpation, indicating that olfactory diagnosis includes both listening to sounds and smelling odors.
This theoretical framework has been maintained to this day. In subsequent textbook versions, various editions have continuously organized and enriched the specific content of olfactory diagnosis, involving various odors from the body and disease room, such as bad breath, sweat, nasal breath, body odor, phlegm, menstrual discharge, bloody odor, foul odor, corpse odor, etc. The identification of these specific odors is of significant reference value for judging disease conditions and physical status. Through the continuous improvement and development of olfactory diagnosis theory, the accuracy and reliability of TCM clinical diagnosis have been further enhanced, laying a solid foundation for the inheritance and development of TCM treatment wisdom.
2 Exploration of the Application of Olfactory Diagnosis in Traditional Chinese Medicine
2.1 Identification of Oral, Nasal, and Bodily Odors and Analysis of Pathogenesis
Variations in Oral Odors: Oral odors may stem from oral diseases or dysfunction of the internal organs. ① Bad Breath: This refers to the foul odor exhaled from the mouth. The Miscellaneous Diseases Source and Flow provides detailed explanations of the causes and treatments of bad breath, indicating that spleen heat can cause sweet or foul breath, recommending the use of Xie Huang San or San Huang Tang; deficiency fire stagnation in the chest and stomach can also lead to bad breath, suitable for using Jia Jian Gan Lu Yin or Jia Jian Xie Bai San for those with thick flavors; lung fire can also cause bad breath, appropriate for treatment with Xiao Feng San. Additionally, the Blood Evidence Treatise suggests that blood stasis can also induce bad breath, manifesting as an unstable complexion accompanied by foul odor. At the same time, oral diseases such as oral ulcers, dental caries, and gingivitis are also significant sources of bad breath. ② Sour Mouth: A sensation of sourness in the mouth, which can be detected by others in severe cases. The Zhuyin Yuanyuan Lun: Vomiting and Other Diseases attributes sour mouth to phlegm-damp stagnation in the upper jiao and spleen-stomach deficiency and cold, leading to undigested food. The Ancient and Modern Medical Mirror suggests that spleen-stomach weakness and liver wood invading earth may also lead to sour mouth. The Blood Evidence Treatise further points out that damp-heat is another cause of sour mouth, similar to how leftover food becomes sour overnight in hot summer. Later physicians continuously enriched and developed this theory, categorizing sour mouth into liver heat type (accompanied by bitter mouth, rib pain, irritability), spleen deficiency wood invasion type (sour belching, poor appetite), and food retention type (sour belching, poor appetite, abdominal distension).
Nasal Odor Changes: The emission of abnormal odors from the nasal cavity is closely related to the pathogenesis of the lung and spleen meridians. For example, patients with nasal congestion often experience yellow, turbid, and foul-smelling nasal discharge due to internal damp-heat, with the pathogenic factor disturbing the brain. The Jingyue Quanshu describes this symptom and its causes in detail, indicating that nasal congestion is mostly caused by the consumption of rich and greasy foods, long-term intake of hot substances, or cold stagnation transforming into fire. These factors lead to damp-heat steaming, causing fluids to overflow and rot, resulting in varying degrees of foul odor. The identification and analysis of abnormal odors in the nasal cavity not only help determine the nature and severity of the disease but also have significant implications for guiding treatment and predicting prognosis. By observing and analyzing the odor changes of phlegm, nasal discharge, and vomit, one can assist in diagnosing and differentiating various types of diseases.
Body Odor: When the body is ill, the skin, as a pathway for the expulsion of pathogenic qi, emits corresponding odors based on the type of pathogenic qi encountered. Infection with warm, toxic pathogens can lead to the corruption of the qi and blood of the internal organs, resulting in foul odors emanating from the skin. If the qi and blood of the internal organs are weak, damp-heat and turbid toxins accumulate, the turbid qi can disperse through the skin, often resulting in a foul odor. For instance, if axillary sweat becomes foul due to damp-heat accumulation, it is known as axillary odor. Additionally, surgical diseases can also cause changes in body odor, such as in patients with gangrene whose toe skin is blackened and rotten, emitting a particularly foul odor; when abscesses rupture and pus flows out, it is often accompanied by a foul odor. The Essentials of Wound Medicine combines the odor characteristics of sores to propose a method of yin-yang differentiation: “Those arising from the internal organs are pale, flat, and soft, with clear or foul pus, fatigue, and weakness, belong to yin.” Zhang Jingyue further proposed standards for judging the prognosis of sores based on their odors: “Weak and obstructed breath, worsening swelling after pus and blood discharge, foul-smelling pus, and unbearable pain are bad signs.” The Secret Teachings of the Cave Heaven provides detailed descriptions of the causes of external sores and the accompanying odor changes, indicating that excessive sexual activity can lead to the rotting of flesh, emitting unbearable foul odors, and emphasizing that pus should present a fishy odor rather than a foul odor.
2.2 Identification of Odors in Excretions and Coughing Up Phlegm and Analysis of Pathogenesis
Identification of Odors in Urine and Feces: Changes in body odors are often caused by external pathogens, dietary stagnation, and other factors. ① Abnormal Feces: The Jingyue Quanshu addresses the characteristics of feces in true heat and false cold conditions, mentioning the possible occurrence of clear water mixed with dry feces and extremely foul-smelling gas, accompanied by strong and slippery pulses. In the Pediatric Awakening: Practical Theory, it states that feces with sour and rotten odors can arise from dietary stagnation, emphasizing that when using digestive medications, one should avoid damaging the qi of the spleen and stomach, and instead choose warming and spleen-strengthening products to assist in digestion. Additionally, damp-heat accumulation can lead to foul-smelling diarrhea; if infectious toxins are involved, it may result in purulent blood stools, with rapid disease progression and abnormal foul odor. ② Odor of Urine: Dai Yuanli in the Essentials of Diagnosis and Treatment: Diabetes points out that the odor of urine changes under the influence of diabetes, such as being neither foul nor sweet but surging violently, indicating a more severe condition. The Classification of Diagnosis and Treatment: Three Types of Diabetes suggests that urine that is not foul but sweet indicates severe deficiency of spleen qi. Foul-smelling urine usually results from damp-heat accumulation in the bladder.
Identification of Odors in Coughing Up Phlegm and Vomiting: ① Coughing up phlegm is a common symptom, and changes in its odor can reflect the nature of the disease and the progression of the condition. Depending on the nature of the pathogenic factor, the odor of phlegm can vary. For example, in the Secret Record of the Golden Bag: Volume Twelve, Feng Zhaozhang elaborates on the differentiation of phlegm and fluid, where changes in the odor of phlegm are one of the important diagnostic criteria. Newly formed phlegm is usually lighter in color and odor, while long-accumulated phlegm may present a yellow, turbid, and sticky state, even carrying foul odors, sour, spicy, fishy, salty, bitter, and blood-streaked flavors. Additionally, the Essentials of Diagnosis and Treatment: Various Coughs also mentions that phlegm coughed up by patients with fatigue-type cough may carry a bloody and foul odor. Lung damp-heat stagnation may also lead to phlegm having a fishy odor. ② Vomiting symptoms can occur in various diseases, thus the identification of the odor of vomit is significant for diagnosis. The odors of vomit can generally be categorized into several types, such as the sour and rotten smell caused by food stagnation, the foul odor presented in cases of excessive stomach fire, and the purulent and bloody foul odor seen in stomach abscesses. By observing and identifying the odors of vomit, one can preliminarily judge the nature and severity of the disease.
Identification of Odors in Menstrual and Vaginal Discharge: Menstruation and vaginal discharge are common symptoms in gynecology, and abnormal changes in their odors can reflect the characteristics and severity of gynecological diseases. ① Normally, menstrual blood is dark red, of moderate texture, and has no special odor. However, in pathological states, menstrual blood may produce abnormal odors. The Medical Canon of the Golden Mirror: Essentials of Gynecology points out that heat and cold are two important factors affecting menstruation. Damp-heat or cold dampness can cause menstrual blood to become thick or clear, accompanied by foul odors. The appearance of these abnormal odors may be related to disturbances in the uterine environment, inflammation, or infection. ② Additionally, vaginal discharge is also a common symptom in gynecology. Healthy women’s discharge should be clear and odorless. However, when the color and odor of the discharge change, it may indicate disease. The Fu Qingzhu’s Gynecology: Vaginal Discharge provides a detailed analysis of the odors and causes corresponding to the five colors of discharge. For instance, liver qi stagnation and spleen deficiency may lead to discharge that is “extremely foul”; damp-heat in the Ren meridian may induce yellow discharge with a “fishy odor”; damp-heat in the liver channel may cause green discharge with a “fishy odor”; and excessive heat may lead to black discharge, which also has a “fishy odor.” These changes in odor are effective clues for disease differentiation and diagnosis.
3 Conclusion
In TCM theory, olfactory diagnosis is an important diagnostic method with a long history and wide application. Although current research on it is relatively weak, its theoretical and practical value cannot be ignored. This study starts from the evolution of TCM olfactory diagnosis theory from the Qin and Han Dynasties to modern times, deeply exploring the application of olfactory diagnosis in TCM. By systematically organizing relevant literature and analyzing its value in clinical practice, it is found that olfactory diagnosis plays an important role in the diagnosis of diseases. Furthermore, modern research should strengthen the exploration of olfactory diagnosis to enhance the accuracy of TCM diagnosis and enrich clinical practice. Future research can further delve into the theoretical foundations of TCM olfactory diagnosis, clarify its role and position in TCM diagnosis, conduct empirical studies to explore the diagnostic value of olfactory diagnosis in various diseases, and strengthen the combined application of olfactory diagnosis with other TCM diagnostic methods to improve the overall level of TCM diagnosis.
—- The content of this article is excerpted from the article “Exploration of the Theory and Application of Olfactory Diagnosis in Traditional Chinese Medicine” published in the Chinese Health and Wellness Journal, author: Li Ping, Rehabilitation Medicine Department, Third People’s Hospital of Hubei Province (Zhongshan Hospital of Hubei Province)
Note: Original content such as references has been omitted.
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