Tongcao (通草, Rice-paper Pith) is the stem pith of a plant — white, elongated, and noticeably thicker than Juncus (Dengxincao). It is a traditional medicinal for clearing heat and promoting diuresis, and appears in many of Zhang Zhongjing’s classic formulas.
My acquaintance with Tongcao began in the pharmacy.
When the clinic was quiet, I liked to wander into the dispensary — examining what the herbs we commonly prescribed actually looked like, what they tasted like. One day I noticed Tongcao. In the pharmacy, Mutong (木通) and Tongcao were stored near each other. Though their therapeutic effects are similar, their properties and flavors are entirely different.
Tongcao is white, long, and brittle. Its surface is quite smooth, and the interior is filled with tiny air pockets, rather like styrofoam. It has virtually no scent, and even less taste — but neither is it astringent. Placed in water, it doesn’t become sticky, and its water absorption is only mediocre. Later, in other settings, I encountered “Great Tongcao” (大通草), considerably larger than the small variety, hollow in the center and quite thick, typically sliced into thin rounds. It must come from a different plant species, though its properties appear similar.
At the time I thought: if this is classified as a heat-clearing, dampness-draining medicinal, it must work primarily through bland percolation — its bland nature allowing it to gently seep dampness outward. Looking at its long, tubular shape, one can imagine it directing heat downward and guiding water outward — a mechanism altogether different from Mutong and other bitter-cold, dampness-drying herbs. Moreover, Tongcao is extremely light. In clinical practice, one must resist habitual thinking: 10 grams of Tongcao is already a generous handful, enough to fill the bottom of a decoction pot.
Later, I made a point of using Tongcao deliberately on several occasions. One particularly memorable case involved an elderly patient with “ascending fire” — dry mouth and tongue, restless agitation, dark-colored urine — whose spleen and stomach could not tolerate cold or cooling substances. Previous practitioners’ heat-clearing prescriptions had all caused gastric discomfort. I added a small amount of Tongcao to a base formula that nourished yin and supplemented qi. The effect was like striking a drum and hearing it sound immediately: the restlessness vanished, sleep improved markedly, and after three doses the tongue coating returned to normal. Most importantly, there was no discomfort whatsoever during the course of treatment. I was genuinely pleased.
I also had a profound personal experience with this herb. After Qingming Festival this year, I developed a perianal abscess for no obvious reason. The pain was unbearable, and on palpation it didn’t feel as though it had come to a head. My thought was to treat it as a perianal abscess (肛痈) with Chinese medicine and spare myself a surgical incision. I used the Pus-Expelling Powder (透脓散), removing the pangolin scales, and added Baizhi (Angelica Dahurica), Mudan Pi (Moutan Root Bark), Yiren (Coix Seed), and Tongcao. To my surprise, after a single dose I had two bowel movements that evening, and the next morning I could sit, stand, and walk without significant pain. Subsequent doses caused no diarrhea, and after completing seven doses I was fully recovered. It truly saved me from a serious ordeal. Chinese medicine has every right to claim authority in treating acute conditions.
中文原文 / Chinese Original
通草是植物的茎髓，白白长长的，比灯心草要粗，是传统的清热利湿药，在张仲景的许多方子中都曾出现过。
我对通草的认识是从药房开始的。
在门诊没人的时候，我喜欢去药房晃荡晃荡，看看平时用的药材都长什么样，尝起来是什么味道，有一次我就看到了通草，药房中木通和通草离得比较近，两种功效虽然相近，但药物的性味却完全不同。
通草是白的、长的、脆的，表面很光滑，里面充满了泡泡，就像是塑料泡沫一样，闻起来没什么问道，尝起来更是没什么味道，但是也不涩，放在水里也不黏，吸水性很一般。后来我在其他地方又见到了大通草，个头比小通草大得多，中间是空心的，相当粗，一般切成了薄片，想必是不同的植物，但是性味看起来差不多。
当时我就在想，这个如果算是清热利湿药，那他估计是淡渗利湿的效果，看他这种长长的像管子的形状，应该就是引热下行，导水外出的作用，跟木通或者其他苦寒燥湿的清热利湿药是完全不同的。而且，通草很轻，临床使用的时候不要惯性思维，10克的通草已经是一大把了，放在锅里满满的一层。
后来，我特别留意地用了几次通草。一次比较经典的是治疗老人上火，口干舌燥，满心烦乱，小便黄赤，但脾胃却又不能耐受寒凉，前医用清热药胃里都会不舒服，我就在滋阴益气的基础上加了点通草，喝了之后效如桴鼓，心烦立除，睡眠明显好转，三付喝完舌苔恢复正常，关键是没有服药期间没有任何不适，很是高兴。
对于这个药我自身也有很大体会，今年清明后莫名其妙得了肛周脓肿，疼的不行，摸上去感觉也没有熟，当时心想就按肛痈治吧，省的挨一刀，就用了透脓散去掉穿山甲，加白芷丹皮苡仁通草，没想到一副下肚，当晚拉了两次，第二天早上起来就不怎么疼了，坐立行走自如，后面再喝也没有拉肚子，喝完7付之后安然如初，真是给我省了大事了，中医药治疗急症是很有发言权的。
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