There are three types of "Liang Gan" (simultaneous infection of yin and yang channels or organs). One is the simultaneous infection of yin and yang channels; another is the simultaneous infection of zang and fu organs; the third is the simultaneous infection of cold and warm pathogens. The so-called simultaneous infection of yin and yang refers to both yin and yang channels simultaneously contracting cold pathogenic factors. What is described as "Liang Gan" in the *Suwen* (Basic Questions) and *Lingshu* (Spiritual Pivot) all refer to this meaning. The etiology of this condition is that latent old cold first resides in the Lower Jiao (lower burner), and new cold subsequently attacks the Upper Jiao (upper burner). The two evils from above and below attract each other, causing the pathogen to rush upward from the Yin aspect, while the new pathogen enters inward from the Yang aspect. There are also cases where both pathogens are contracted simultaneously. This must result from wearing thin clothes and being exposed to the elements, or traveling far in the cold, leading to sweating after physical exertion, allowing the pathogen to enter through deficiency. At this time, the pathogen comes overwhelming like a blanket covering heaven and earth. How could there be time for gradual transmission through the meridians, progressing from shallow to deep? How could there be time for balanced yin-yang coordination or adherence to standard treatment protocols? Therefore, when Taiyang disease (Taiyang channel syndrome) and Shaoyin disease (Shaoyin channel syndrome) occur together, they may not fail to present with symptoms of Yangming disease (Yangming channel syndrome) and Taiyin disease (Taiyin channel syndrome). When Yangming disease and Taiyin disease occur together, they may not fail to present with symptoms of Shaoyang disease (Shaoyang channel syndrome) and Jueyin disease (Jueyin channel syndrome). However, the pathogen ultimately requires an entry route. Careful examination of the mechanism reveals distinctions between primary and secondary conditions, and between severe and mild presentations.

The so-called simultaneous infection of zang and fu organs refers to the simultaneous contraction of cold pathogenic factors by the exterior meridians and the internal organs, not referring to the transmission of disease from fu organs to zang organs or vice versa. This may arise from dietary injury to the stomach and intestines, or from respiration allowing pathogens to enter the Danzhong (Chest Center/Shanzhong). Therefore, one must be extremely cautious regarding children eating or crying in the wind. If the exterior is affected by wind-cold, and internal cold rushes upward to the Lung (Lung) and downward invades the Kidney (Kidney), then amidst aversion to cold, fever, and stiffness/pain of bones and sinews, there is added suffering from cough, vomiting, diarrhea, and abdominal pain. Zhang Zhongjing advocated treating the interior first and then attacking the exterior, which is a method of slow treatment. For acute cases, warming the middle and releasing the exterior are used simultaneously. Wind disturbing the middle causes extremely severe conditions, such as Huoluan (cholera-like disorder with vomiting and diarrhea) and tendon retraction (cramps/spasms); only Guizhi Tang (Cinnamon Twig Decoction) or similar agents containing Cinnamon Twig are sufficient to control it.

The so-called simultaneous infection of cold and warm refers to the co-latency of cold and warm toxic pathogens, not referring to Shanghan (Cold Damage) transforming into Wenbing (Warm Disease), or Wenbing turning into cold. External pathogens harming the body are called "toxic," whereas heat generated by internal Qi transformation cannot be called "toxic." Since it cannot be called simultaneous infection, Shanghan may present with fatal cold syndromes at onset, but never fatal heat syndromes at onset. Those who die of heat at onset do so due to prolonged neglect of treatment or because warm pathogens were already latent internally. Conversely, Wenbing may present with fatal heat syndromes at onset, but never fatal cold syndromes at onset. Those who die of cold at onset do so due to prolonged neglect of treatment or because cold pathogens were already latent in the Lower Jiao. A common scenario involves dryness pathogen, resulting from long sunny periods in autumn, lying latent in the Danzhong via respiration. After Frost's Descent, when weather suddenly turns cold and pores open, the pathogen takes advantage, presenting with alternating chills and fever, severe pain, and initial confusion/coma, delirium, coarse voice, and thirst craving water. Another scenario involves summerheat latent in summer, suppressed by autumn coolness, unable to vent, and manifesting in winter after contracting cold. Symptoms include vexatious heat in the chest, feeling like broken skin, ice-cold feet, and night-time feverish heat like burning, with restlessness and insomnia; this is due to summerheat toxicity in the Blood level. Yet another scenario involves cold latent in the Lower Jiao during winter, manifesting in spring after contracting wind-warmth. Symptoms begin with upper respiratory distress, coarse breathing sounding like a pot, gradually progressing to facial/ocular edema, coma, regurgitation, and dry retching. The general principle is to treat the warm component first, then the cold component, which differs from treatments for true cold/false heat or true heat/false cold patterns.