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Bohe (Menthae Haplocalyx, 薄荷): Its taste is pungent; its aroma is clear, rich, and penetrating. Its nature is neutral. In small doses, it is cooling; in large doses, it becomes heating (for instance, when fresh Bohe juice is applied externally to the skin, a small amount feels distinctly cool, while a large amount causes a burning sensation). Its efficacy can penetrate internally into the sinews and bones, reach externally to the muscle layer, unblock the Zang-Fu organs, and traverse the meridians. After ingestion, it induces the excretion of cool sweat, making it a crucial herb for treating Warm Diseases (Wen Bing) that require resolution through sweating. If used in small doses, it is also effective in harmonizing internal injuries, treating pain caused by stagnation of Liver Qi and Gallbladder Fire, or sudden epilepsy and convulsions due to internal stirring of Liver Wind, along with headache, eye pain, nasal sinusitis (Bi Yuan), nasal congestion, toothache, swelling and pain of the throat, and painful stiffness of the limbs. It can treat all disorders characterized by wind-fire stagnation and heat. For dysentery in its early stage accompanied by external contraction, Bohe is also suitable; it disperses the external pathogenic factors and simultaneously clears heat in the intestines, thereby facilitating recovery. Furthermore, Bohe is adept at eliminating bacteria (since Bohe Bing [Borneol] is good at eliminating cholera toxins, it follows that Bohe is also capable of disinfection); it drives away foul odors and is an important herb for various cases of cholera and Sha Zheng (sand syndrome). Due to its pungent and cooling nature, it is also effective in venting rashes and curing skin pruritus, making it a commonly used item in pediatrics.

When treating Warm Diseases requiring diaphoresis, Bohe is used, just as Mahuang (Ephedrae Herba) is used for treating Cold Damage (Shang Han) requiring diaphoresis. After taking Mahuang, hot sweat is produced; this hot sweat resolves cold pathogens, hence it is suitable for Shang Han. After taking Bohe, cool sweat is produced; this cool sweat clears warm pathogens, hence it is suitable for Wen Bing. If Mahuang were used to induce sweating for a Warm Disease, or Bohe for a Cold Damage, generally no sweat would be produced; even if sweat were produced, it would certainly not cure the disease.

In ancient times, Bohe was originally named "Ke" and was used as a vegetable rather than a medicine. It was not recorded in either the *Shennong Bencao Jing* (Divine Farmer's Materia Medica) or the *Mingyi Bielu* (Record of Famous Physicians). It was only listed among medicinal substances during the Tang Dynasty. Therefore, none of the formulas in the *Shanghan Lun* (Treatise on Cold Damage) use Bohe. However, upon careful examination of the formulas in the *Shanghan Lun*, there are indeed instances where Bohe should have been used. Because it was not yet listed as a drug at that time, formulas that required Bohe had to substitute it with other herbs. Let us analyze some Shang Han formulas: for example, Mahuang in the Mahxing Gan Shi Tang (Ephedra, Apricot Kernel, Gypsum, and Licorice Decoction) could be replaced by Bohe. The Mahxing Gan Shi Tang originally treats symptoms of sweating, wheezing, and absence of high fever. Since there is "no high fever," it implies that heat still exists. The reason Mahuang is used despite the presence of heat is to drain Lung Qi and relieve wheezing. However, since Mahuang can drain Lung Qi and relieve wheezing, Bohe can do so as well (the pungency of Bohe suppresses excessive Lung Qi and is good at searching out Lung Wind). Why use Mahuang to treat heat with heat, when one could use Bohe to treat heat with coolness? Similarly, Gegen (Puerariae Radix) in various formulas containing Gegen could also be replaced by Bohe. Gegen is originally used to release exterior Heat in the Yangming channel. Gegen's cooling property is inferior to Bohe, and its power to release the exterior is far less than that of Bohe. Thus, why use Gegen when Bohe would be superior? This does not contradict ancient teachings. When drugs were not yet comprehensive, the formulas created by the ancients necessarily had imperfections. There is no other reason but the limitations of their time. We, living in an era where medicinal resources are abundant, fail to adapt and innovate according to circumstances, which means we have not truly understood the intent behind the ancients' formulation of medicines. Researchers of Shang Han in the medical field should ponder my words deeply.