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Mahuang (Ephedrae Herba) inherits the clear, yang, and vigorous qi of heaven and earth; therefore, its taste is bitter and its nature is warm. Its flavor and aroma are both thin, making it light, clear, and floating upward; it belongs to Yang and possesses ascending and dispersing properties. It is non-toxic. It enters the Hand-Taiyin Lung Meridian, the Foot-Taiyang Bladder Meridian, and also traverses the Hand-Shaoyin Heart Meridian and Hand-Yangming Large Intestine Meridian. Because it is light, it can dispel excess, thus treating Shanghan (Cold Damage) and serving as the premier herb for releasing the muscle layer.

Mahuang treats wind-strike, Shanghan, headache, Wen Nue (Warm Malaria), and numbness of the skin and flesh; it induces sweating to release the exterior. In winter, it is miraculous for typical Shanghan; in early spring, it is excellent for true epidemics. It vents heat from the Wei (Defensive) level, treating black spots and red rashes caused by heat toxicity, and removes cold from the Ying (Nutritive) level to relieve headache and fever. However, it should not be added for Wen Nue in late spring, and it is strictly prohibited for cold epidemics in summer and autumn. Furthermore, it breaks up accumulations and hardness, and is particularly effective in subduing cough with counterflow, flaccidity, and bi-syndrome, as well as phlegm-wheezing and asthma. For deep-penetrating cold pathogens, only Mahuang can drive them out, provided that the skillful use of assistant and guiding herbs is applied. Combined with Qi-moving herbs to assist power, it yields sweat from the Wei level; combined with Blood-nourishing herbs to assist fluids, it yields sweat from the Ying level; combined with warming herbs to assist Yang, it drives out Yin-congealed cold toxins; combined with cooling herbs to assist Yin, it resolves hot epidemic pathogens. However, excessive consumption by patients will inevitably lead to Wang Yang (collapse of Yang), due to its light and clear nature causing excessive ascending, floating, and exterior-releasing effects. The root nodes (Genjie) stop sweating with significant efficacy because they possess a nature that travels well on the body surface, capable of guiding other herbs to directly consolidate the Cou Li (pores and interstitial spaces). Mahuang’s shape is hollow in the center, dispersing cold pathogens and releasing the exterior; its nodes are closed inside, stopping night sweats and securing deficiency.

Main Indications (Integrated with Smallpox/Rash Diseases): Vents Wei excess, removes Ying cold, regulates blood vessels, unblocks the nine orifices, opens pores, induces sweating and releases the muscle layer, and eliminates red/black spot toxins. For smallpox/rash lesions that have inverted, retracted, or turned black and sunken, take half liang of Mahuang with roots and nodes removed. First soak in boiling water, dry, cut finely, then soak in wine for a long time. Stir-fry in a clay vessel until charred black, then decoct with water and drink all while hot. After ingestion, avoid exposure to wind, lest the lesions reappear. Decocting with wine yields even faster results. It may also be used for delayed eruption. In cases of severe cold contraction in winter preventing rash eruption, accompanied by fever and aversion to cold, Mahuang is used to disperse cold pathogens. However, once the rash points appear, it is contraindicated. Another condition involves extremely hard rashes that refuse to fill with pus, known as "Iron Armor Rash"; this herb causes the rash to ulcerate, creating a chance for survival. Nevertheless, its opening and draining action is too strong; misuse leads to exterior deficiency and Qi collapse.

Commentary: Mahuang is light and dispels excess, ranking first among dispersing herbs. It is suitable only in winter when there is genuine cold pathogen on the exterior. If there is no cold pathogen, or if the cold pathogen is interior, or in conditions like Shanghan with sweating, even if fever and aversion to cold are present, it must not be used. Even in syndromes suitable for sweating, it should not be taken in excess, because sweat is the fluid of the Heart; mistaken or excessive sweating agitates Heart Blood. This may lead to collapse of Yang or epistaxis (nosebleed); how can one not be cautious? Therefore, Mahuang is the herb for treating Wei excess, while Guizhi Tang (Cinnamon Twig Decoction) is the herb/formula for treating Wei deficiency.