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Current physicians, upon seeing patients with exogenous diseases, immediately claim they have contracted "Shi Xie" (Seasonal Pathogenic Factors), and subsequently diagnose it as a "Seven-Day Syndrome"; if it does not resolve within seven days, they label it a "Fourteen-Day Syndrome."

They are unaware that there are three main categories of exogenous etiology: one is Shang Han (Cold Damage), the second is Shi Xie (Seasonal Pathogenic Factors), and the milder form is referred to as Gan Mao (Common Cold).

Only in Shang Han (Cold Damage) is the progression through meridians discussed. The *Huangdi Neijing* (Yellow Emperor's Inner Canon) states: On the first day, the disease is in the Taiyang (Greater Yang) meridian; on the second day, in the Yangming (Bright Yang) meridian; on the third day, in the Shaoyang (Lesser Yang) meridian; on the fourth day, in the Taiyin (Greater Yin) meridian; on the fifth day, in the Shaoyin (Lesser Yin) meridian; and on the sixth day, in the Jueyin (Terminal Yin) meridian. By the seventh day, the transmission cycle completes, and the pathogenic factor in the Taiyang meridian begins to wane; by the eighth day, the Yangming pathogen wanes; by the ninth day, the Shaoyang pathogen wanes; by the tenth day, the Taiyin pathogen wanes; by the eleventh day, the Shaoyin pathogen wanes; and by the twelfth day, the Jueyin pathogen wanes. Treatment should focus on unblocking the respective organ meridians, after which the disease will gradually decline and resolve. This merely follows the principle of the seven-day cycle and does not support the theory of "re-transmission." The concept of re-transmission stems from erroneous annotations by Cheng Wuji, which were long ago refuted by Ma Yuantai. Since there are several meridians separating the Jueyin from the Taiyang, how could the pathogen suddenly transmit directly to the Taiyang? Even according to the seven-day transmission described in the *Neijing*, it clearly instructs practitioners: if the disease is known to be in the Taiyang, treat it in the Taiyang without waiting for it to transmit to the Yangming; if in the Yangming, treat it in the Yangming without waiting for transmission to the Shaoyang; if in the Yang aspect, treat it in the Yang aspect without waiting for it to enter the Yin aspect. Furthermore, the term "day" in "first day, second day" should not be interpreted rigidly as calendar days, but rather indicates the sequence of transmissions (e.g., first transmission, second transmission). Human constitutions vary in deficiency and excess. Some individuals have robust Stomach Qi; when the Taiyang meridian is affected, the pathogen may remain there for two or three days without transmitting to the Yangming. Others have inherently weak Wei Qi (Defensive Qi), causing the Taiyang pathogen to persist throughout. How can rigid methods be applied universally? These discussions pertain specifically to Shang Han (Cold Damage). In the Jiangnan region, true Shang Han (Cold Damage) is rare, making formulas such as Mahuang Tang (Ephedra Decoction) used by Zhang Zhongjing largely inappropriate.

Generally, Shi Xie (Seasonal Pathogenic Factors) are most common. Shi Xie (Seasonal Pathogenic Factors) refers to pathogens contracted from winter cold, spring warmth, summer heat, or autumn dryness/cold. Additionally, abnormal seasonal temperatures—such as winter being warm instead of cold, spring being cold instead of warm, summer being cool instead of hot, or autumn being hot instead of cool—are also classified as Shi Xie (Seasonal Pathogenic Factors). When Shi Xie (Seasonal Pathogenic Factors) involves cold and chill, entering via the Taiyang (Greater Yang) meridian, symptoms necessarily include headache and stiffness of the head and neck, and rigidity of the lower back and spine. If it transmits to the Yangming (Bright Yang) meridian, symptoms necessarily include fever, eye pain, nasal dryness, and insomnia. If it transmits to the Shaoyang (Lesser Yang) meridian, symptoms necessarily include hypochondriac pain, heavy sensation in the ears, and bitter taste in the mouth. In these cases, treatment should follow the methods for the Three Yang meridians to prevent the pathogen from penetrating inward. This is referred to as "Minor Shang Han (Cold Damage)," requiring mild therapeutic approaches. When Shi Xie (Seasonal Pathogenic Factors) involves warmth and heat, it generally enters via the mouth and nose, bypassing the Taiyang (Greater Yang) meridian, often reaching the Membrane Source (Mo Yuan, a location between the exterior and interior) via the Yangming (Bright Yang) meridian. If left untreated, it easily invades the Pericardium (Xin Bao), leading to concerns about mental restlessness and delirious speech. Treatment should employ acrid-cool methods, primarily using cooling herbs with acrid herbs as auxiliaries. If excessive summer heat causes irritability and anhidrosis (absence of sweating), Baizhu Tang (White Tiger Decoction) or Tiansheng Baizhu Tang must be used to induce profuse sweating and resolve the condition. However, one must first verify the presence of intense thirst craving for cold beverages to confirm true heat retention; otherwise, these drugs should not be administered recklessly.

Gan Mao (Common Cold) involves only slight exogenous invasion, requiring mild dispersing treatments. If accompanied by food stagnation, adding digestive and promoting circulation agents allows for recovery with a single prescription. Yet some physicians still label it a "Seven-Day Syndrome." Initially, Gan Mao (Common Cold) may present with alternating chills and fever, which these physicians misdiagnose as incipient malaria, frequently prescribing Chai Hu (Bupleuri Radix) to force its development into malaria. They fail to realize that Chai Hu (Bupleuri Radix) is specific to the Shaoyang (Lesser Yang) meridian, whereas early-stage Gan Mao (Common Cold) does not involve the Shaoyang (Lesser Yang) meridian. Using Chai Hu (Bupleuri Radix) unjustly attacks healthy Qi, potentially prolonging the Gan Mao (Common Cold). Worse still, some physicians equate Gan Mao (Common Cold) with Shi Xie (Seasonal Pathogenic Factors) and prescribe Dayuan Yin (Reach the Origin Decoction) from *Wen Yi Lun* (Treatise on Pestilential Diseases). If ineffective, they resort to purgative methods, harming patients without remorse, which is truly lamentable.

*Wen Yi Lun* (Treatise on Pestilential Diseases) was written by Wu Youke, a figure from the late Ming Dynasty. During his time, continuous wars and famines caused widespread displacement, with millions dying in ditches. The qi of corpses transformed into pestilential qi, spreading through the world. Those infected suffered household-wide contagion, with infinite transmission potential. While ancient texts occasionally mentioned pestilence, none were dedicated solely to it. Wu Youke correctly identified that pestilential pathogens enter via the mouth and nose and reside in the Membrane Source (Mo Yuan), thus creating Dayuan Yin (Reach the Origin Decoction) and advocating urgent purgation. His methods were effective in that specific context, leading him to write the two-volume *Wen Yi Lun* (Treatise on Pestilential Diseases), offering a novel approach beneficial to medicine. However, his work lacks rigorous detail. Its methods are applicable only during actual pestilence years. Current Shi Xie (Seasonal Pathogenic Factors) are not pestilence; thus, applying these methods is reckless. Treating Shi Xie (Seasonal Pathogenic Factors) as equivalent to pestilence and prescribing Dayuan Yin (Reach the Origin Decoction) initially, repeatedly administering Cao Guo (Tsaoko Fructus) and Hou Po (Magnolia Bark), leads to unbearable dryness-heat. Subsequently, Da Huang (Rhei Radix et Rhizoma) is used for purgation. Survivors are credited, while deaths are blamed on untreatable disease, though the outcome was self-inflicted. The use of Dayuan Yin (Reach the Origin Decoction) for Shi Xie (Seasonal Pathogenic Factors) is inexplicable and strange. Most astonishing is treating fatigue-induced chills and fever as Shi Xie (Seasonal Pathogenic Factors) and administering Dayuan Yin (Reach the Origin Decoction). Fatigue-induced fever is mild; persistent sweating without fever reduction indicates Yin Deficiency. Misdiagnosing this as Shi Xie (Seasonal Pathogenic Factors) obstruction and using Dayuan Yin (Reach the Origin Decoction) violates the prohibition against "treating deficiency as excess," causing harm. I know relatives and friends who suffered from this ignorance, leaving me to sigh in vain. My family members studying medicine must read widely, seek profound principles, avoid relying on simplistic texts, and refrain from rash treatments. Fatigue-induced chills and fevers often resemble exogenous diseases, but differentiation is crucial: the fever is usually mild, decreases upon pressure, and feels lighter; chills are intermittent or variable, relieved by warmth; slight sweating during fever does not reduce it; palm heat exceeds back-of-hand heat; headaches may occur intermittently with varying intensity; although the body feels weary and painful, and spirit is fatigued, consciousness remains clear without delirium. In such cases, regulating Qi and Blood, along with rest, ensures natural recovery. For Yin Deficiency due to fatigue, where sweating fails to reduce fever, herbs like Sheng Di Huang (Rehmanniae Radix) and Dang Gui (Angelicae Sinensis Radix) nourish Yin and clear heat, resolving the fever and illness. Misdiagnosing this as exogenous disease violates the prohibition against "treating deficiency as excess." Further misdiagnosing it as Shi Xie (Seasonal Pathogenic Factors) obstruction and using Dayuan Yin (Reach the Origin Decoison) recklessly is rarely non-fatal.