Fever With a Rash That Won’t Go Away? Doctor Zhang Xichun’s Case of Warm Disease with Sha Zhen Rash — Bai Mao Gen, the Wild Grass That Finished the Job

Search terms a patient might use: fever with a rash / rash that came out but the fever won’t go away / restless and agitated / dark, scanty urine / heat that lingers after measles

Medical terms for this pattern: warm disease (wen bing) · sha zhen rash disease · latent heat transforming into heat (fu qi hua re) · heart-kidney disharmony · rash toxin failing to transmit outward · bai mao gen (cogongrass root)

Opening: external-contraction illness — worth talking through thoroughly

Doctor Luo Dalun continues telling Doctor Zhang Xichun’s stories — today it is warm disease combined with sha zhen, which in plain words is fever with a rash. Why does he keep dwelling on external-contraction diseases? Because they are what people meet most often in a lifetime — the common cold, for example. The number of people who get tumors is small, but the number who catch colds is enormous.

💬 Note from Doctor Luo: When this episode was recorded, the pandemic was still serious: the number of patients overseas was huge — globally it had reached 700,000 — and experts predicted there could be a second wave in the second half of the year. So everyone should be very cautious — the more you learn about external-contraction illness, the better; it will certainly help. Today’s case also hides a particularly interesting herb: bai mao gen (cogongrass root). It grows everywhere along field ridges, yet few people know its power to resolve heat toxin and treat rashes.

Who was the patient? A manager who knew medicine himself

The patient was Su Xiaochen, 45 years old, manager of the Huaxin Company office in Tianjin District 2. Doctor Zhang wrote down his occupation again — a unit leader, a man who managed things.

💬 Note from Doctor Luo: As soon as you see that position you know — a man like this worries and works hard; keep that in mind, and we’ll talk about it later. How did he fall ill? Mr. Su originally knew medicine well — he himself understood Chinese medicine. When the rash epidemic was going around, he went out repeatedly to treat others, and caught the infection himself. A doctor who treats patients and catches the very disease he treats — that is how this illness began.

What is sha zhen? First, a story that tugs at the heart

What kind of disease is sha zhen? In the past, some contagious illnesses required “erupting sha and rash,” and some plagues even carried this signature. Don’t underestimate it — childhood measles, for instance, was historically a very high-mortality infectious disease.

💬 Note from Doctor Luo: My mother told me — my maternal grandfather, in the mountains of Liaoyang county, was a famous village doctor, recorded in the county annals. When measles epidemics raged, some children reached a critical state; the family was poor, could not afford a doctor, and felt the child was beyond saving, so they wrapped the child in a straw mat and left it at the foot of the mountain. Some of those abandoned children really died; some were still barely breathing. My grandfather picked up the ones that still had breath, brought them home, treated them with Chinese medicine, and when they recovered, carried them back to their families. A few years ago I returned to my hometown to visit the grave, and I met villagers praying at my grandfather’s grave: “So-and-so in our family has such-and-such an illness — please, Old Master Wang, show your power and help him.” Ordinary people truly remember the lives you saved — it is still passed down by word of mouth after all these years. So remember this: rash disease has always been a big deal.

He treated himself first: the rash must come out, never be pushed back

Manager Su understood medicine, so in the first few days he treated himself, using herbs that transmit the rash and clear heat. Was that the right idea? Yes!

💬 Note from Doctor Luo: The rash must be allowed to move outward. If you see a rash and immediately push it back — bad: the poison attacks the heart, and the person may be finished. If the rash comes out smoothly, that is the favorable course, a normal sign of recovery. So transmission outward is the principle; you do not suppress it.

But here was the problem: the rash had already erupted, fully come out — and still the fever would not go away. There was nothing for it: he hurriedly called Doctor Zhang.

How sick was he? Great heat in exterior and interior, restless without a moment’s peace

When Doctor Zhang examined him, several key facts stood out:

• Heat in both exterior and interior — the patient felt blazing heat inside and out;
• Extreme restlessness, no moment of calm — his heart was so agitated he could not be still for an instant;
• The pulse weak and faint, barely rising — no strength in the pulse, meaning insufficient upright qi (zheng qi);
• Tongue coating thin, white with slight yellow — once the coating turns even slightly yellow, the heat in the body is already severe;
• Stool once a day, unformed; urine dark red and scanty — deep color and small volume, more evidence of internal heat.

💬 Note from Doctor Luo: That restlessness is crucial — it is usually connected to heat in the heart channel. Remember that sentence. A weak pulse means insufficient upright qi; a yellow tongue coating means heavy heat; dark scanty urine is still heat — heat signs everywhere, yet the upright qi is deficient. That is the whole pattern of this illness.

What did Doctor Zhang think? Latent heat transforming, heart and kidney not communicating

Doctor Zhang’s analysis: this is latent heat transforming into heat (fu qi hua re). We discussed it before — “injured by cold in winter, you will surely suffer warm disease in spring.” In winter the cold pathogen enters and hides; it does not erupt immediately. When spring arrives and the weather warms, it transforms into heat and bursts out.

💬 Note from Doctor Luo: Why does it hide in winter and transform in spring? Let me tell you — people with this constitution are necessarily yin-deficient — usually with insufficient fluids or insufficient kidney essence. In winter it is cold outside; the external pathogen enters but does not erupt immediately, because the conditions for eruption are not yet right. In spring, when it warms up outside, sweat releases, the body grows hotter, qi and blood circulate actively, the pathogen begins to struggle with the upright qi — and it transforms into heat all at once. So the latent-heat onset of “winter cold, spring warmth” is usually the pattern of a yin-deficient constitution.

And he had run into the rash epidemic outside: the external pathogen entered and slipped along the san jiao fatty membranes into shaoyin, injuring kidney qi, so that kidney water could no longer ascend to nourish heart fire — heart and kidney could no longer communicate, hence the agitation and endless restlessness. Yin deficiency also made the deficiency heat stronger, so the heat signs were obvious. Doctor Zhang added one very important sentence: although this is warm disease, it is no different from shaoyin cold damage with heat.

💬 Note from Doctor Luo: This shows that cold and warm illness are actually one body — in certain patterns they produce the same symptoms, and the treatment should use the same method. Doctor Zhang never rigidly separated cold disease from warm disease; he looked at the pattern present before him.

The prescription: White Tiger plus Ginseng — Doctor Zhang’s signature move

How to treat it? Bai Hu Jia Ren Shen Tang (White Tiger plus Ginseng Decoction) — Doctor Zhang’s killer move: whenever qi-level heat is strong, use the White Tiger Decoction; when the upright qi is insufficient and the pulse lacks strength, add ginseng to support the upright qi, plus a little something to transmit the rash toxin outward.

The formula is simple: raw gypsum (ground fine), 2 liang; wild codonopsis (ye dang shen), 4 qian; Trichosanthes root (tian hua fen, the root of the gourd vine), 8 qian; raw Huaishan yam (sheng huai shan yao), 8 qian; fresh cogongrass root (xian bai mao gen), 4 qian; licorice (gan cao), 2 qian. Decoct into two cups and take warm in two divided doses.

💬 Note from Doctor Luo: Raw gypsum clears great qi-level heat — whenever Doctor Zhang met warm disease with the pathogen at the qi level, he used it; we have said this many times. Wild codonopsis supports the upright qi — when you have insufficient upright qi and still must clear heat, gypsum paired with codonopsis is his fixed rule, his standard. Tian hua fen is the Trichosanthes root — it moistens dryness, nourishes yin, and resolves toxin. Raw Huaishan yam supports the upright qi. And what is the fresh cogongrass root for? Transmitting the rash toxin outward — the focus of a moment. Licorice harmonizes the herbs and also resolves toxin. Look at this formula: it is exactly the White Tiger plus Ginseng, with tian hua fen replacing zhi mu, raw yam replacing rice, plus fresh cogongrass root. Very simple.

One dose worked — but after noon it burned again

After the first dose, the heat retreated by more than half, the restlessness eased, and he could sleep peacefully. But on the next day, after noon, the fever and restlessness returned just as before, and the pulse was still without strength.

Doctor Zhang thought: not enough power. He immediately raised the gypsum to 3 liang and the wild codonopsis to 5 qian, increased the dose, decocted three cups to be taken in three divided doses, and added one raw egg yolk to each dose.

💬 Note from Doctor Luo: About the raw egg yolk method — a classmate of mine, an old Chinese medicine doctor, posted a literature note on Weibo the other day specifically on this: some people beat a raw yolk into the finished decoction and get diarrhea — why? In ancient times, eggs were laid fresh and used right away. Today’s eggs pass through the chicken farm, the shop, and the fridge; they may sit for a very long time and become contaminated, so beating one in can upset the stomach. How do other old doctors use it? Boil the egg, take out the yolk, and decoct it together with the herbs; or boil the yolk in water first and use that water to decoct the herbs — either way works. Zhang Zhongjing said “add one egg yolk”; he did not say you must beat it in. If you do beat it in, use a fresh egg that has not been stored long. Remember this.

Even a famous doctor meets problems: the cold-cooling medicine must stop

Taking the medicine with the egg yolk, the illness gradually healed — but soon it relapsed, and moreover the stool came twice a day.

Doctor Zhang began to reflect: stool twice a day means the spleen-stomach has been slightly injured, and the cold-cooling medicine can no longer be taken. What to do?

💬 Note from Doctor Luo: You see — even Doctor Zhang ran into problems. But he was a famous doctor: when he hit a problem, he thought. And in that thinking, he was suddenly enlightened and devised a way to treat this illness: use fresh cogongrass root. This is the most brilliant stroke of the whole case: the White Tiger plus Ginseng failed twice, and in the end a single wild grass finished the job.

Bai mao gen: the “treasure” everywhere on the field ridge

Everyone has actually seen bai mao gen — it is cogongrass, growing everywhere in the earth, especially in the north; it is all over the place, you just do not recognize it. On its stem grows a long, white, fuzzy spike. This ordinary thing has an extraordinary number of uses.

Doctor Zhang held that bai mao gen is sweet in taste and cool in nature, hollow with nodes — jointed, hollow inside, with twelve small holes on the cross-section, translucent all through, like the zhen trigram. It is supremely good at transmitting the latent heat of the viscera and pushing the rash toxin outward — for chickenpox and rash poison, it helps push the toxin out and transmit it to the surface.

💬 Note from Doctor Luo: The first function of bai mao gen is to push heat toxin out through the urine. When there is heat in the body, it can drain the visceral toxin out through the urine and resolve it — especially when there is heat toxin in the lower burner; boiling bai mao gen alone in water is enough. Second, it is white in color and enters the lung, and it is hollow inside, so it can clear lung heat — treating cough and wheeze caused by heat. Children who get nosebleeds in spring because yang qi is vigorous and heat is in the body — soak bai mao gen in water and give it to them, and it stops. Third, chewing it is sweet; sweet taste enters the spleen — it is excellent at clearing spleen-stomach deficiency heat, nourishing stomach yin, and generating fluids — cough with blood, spitting blood, nosebleed, and blood in the urine caused by lung-stomach heat all respond remarkably to bai mao gen.

A personally-tested story: blood in the urine, cured in two days with bai mao gen

Doctor Luo also told a story he experienced himself — when he was in Shenyang, he had a good brother who drank often. One day the man came to him suddenly: his urine was full of blood. He went to the hospital and the test came back — red blood cells everywhere. What to do?

💬 Note from Doctor Luo: I said: just soak bai mao gen in water and drink it as tea. After two days — cured. So bai mao gen is especially good at treating lower-burner heat toxin caused by heat: chronic nephritis, for instance, is very often a heat pattern — stasis and heat hidden in the kidney channel — and the formula must include bai mao gen. Urinary tract infection, with painful urination and red urine — bai mao gen works very well too. Many people think bai mao gen is only a lower-burner herb; but when there is heat in the lung channel or the rash toxin cannot transmit outward, it is just as skilled.

How to prepare it? Fresh and dried each have their rules

Doctor Zhang especially prized fresh bai mao gen — go dig it up in the field, wrap it in mud, and it will never spoil. How to use the fresh root? His method is special:

💬 Note from Doctor Luo: Cut the fresh bai mao gen into fine segments, put them in cool water, bring it to a boil, then immediately take it off the fire; wait half an hour, bring it to a boil again, take it off, wait half an hour again… until the bai mao gen all sinks to the bottom — then the decoction is done; drink it as a beverage — the heat-clearing effect is best. In the city, where you cannot dig fresh root, the dried root from the pharmacy also works: pour boiling water over it; when it cools, heat it over the fire briefly — best not to let it come to a boil, just heat it a little; take it off, cover it and steep for about an hour, discard the dregs, and drink the water. Speaking from my own practice: boiling the dried bai mao gen briefly is fine too — after it comes to a boil, let it roll a couple of times, turn off the fire, let it steep and slowly settle, steep a while longer, and drink that water — this is imitating the fresh-root method.

The closing formula: six liang of fresh cogongrass root, two doses to cure

When he used it for Manager Su, Doctor Zhang used fresh bai mao gen, chopped, 6 liang — a very large dose — added 5 cups of cool water, brought it to a rolling boil on the stove, then took it off the fire; after about ten minutes he brought it to a boil again and took it off again, back and forth like this. When the bai mao gen had all settled to the bottom, the decoction was done. Drink it all at once while hot — ideally working up a slight sweat.

💬 Note from Doctor Luo: What is bai mao gen doing here? Clearing heat, and also resolving toxin and transmitting the rash toxin outward — when there is a rash, it can transmit the toxic blood outward, transmit it to the body surface. Doctor Zhang told him: drink it this way. And with this method, after two doses the illness suddenly healed — completely recovered all at once.

Doctor Zhang’s reflection: fifty years of practice, and this was the closer

After the illness was cured, Doctor Zhang wrote a passage of reflection after the case record — well worth reading.

💬 Note from Doctor Luo: He said this illness may have been somewhat slighted at first — the latent poison was diffused through the three burners, present throughout the body’s channels and collaterals, and at that point transmitting it outward is not easy. But bai mao gen carries the very first qi of shaoyang — in spring it is the first thing to sprout; cool yet able to scatter. Not only is it hollow, it also has small holes all around it — twelve small holes, translucent and penetrating, able to pass through channels, collaterals, and viscera, reaching even the finest places. Used in a large dose, it can expel the toxic heat between the viscera and channels completely, transmitting it to the body surface. Once the poison is cleared away, the body naturally recovers. Doctor Zhang then reflected with emotion: in fifty years of clinical practice, how many times had he used the White Tiger plus Ginseng Decoction? It worked at his fingertips, always effective — yet in this illness it failed twice, and in the end bai mao gen finished the job. That truly was something he had not expected. At the time it was a flash of insight about bai mao gen’s nature; and from then on he used bai mao gen many times, always with excellent results. In the future, when treating rash-type diseases, you can borrow this method; if the excess signs are especially clear — pulse surging, slippery, rapid and forceful — you may still use raw gypsum heavily, but paired with bai mao gen, the effect is excellent too.

Why didn’t bai mao gen become famous?

Doctor Luo ends with a wistful passage — bai mao gen is so good, why has it not become as widely known as raw gypsum or Huaishan yam?

💬 Note from Doctor Luo: Doctor Zhang was especially good at appreciating the nature of each medicine and opened up many new application fields for Chinese medicine — raw gypsum and Huaishan yam are both fields he broadened. Bai mao gen was also his unique experience, used with great flexibility. But why did it not spread? Because this case was in Tianjin — an experience he summarized only in his late years. Not long afterward he passed away, with no time to write it repeatedly and refine it. If Doctor Zhang had lived a few more years, or if he had realized it while in Shenyang, bai mao gen would certainly have become one of his signature herbs. Today when we use bai mao gen, it is basically for lower-burner heat — blood in the urine, urinary tract infection — but in whole-body formulas for resolving toxin — lung-channel heat, rash toxin failing to transmit outward — it is rarely used. That truly is a pity.

Closing: in daily life, you too can use bai mao gen

Today’s case itself is simple, with little analysis, because it resembles the previous episodes — but the rash and bai mao gen deserve more discussion.

💬 Note from Doctor Luo: Someone asks: in hot weather I break out in a rash all over — what should I do? I think soaking some bai mao gen water and drinking it, transmitting it outward, clearing the summer heat — the effect will be very good. And bai mao gen is a very gentle herb, sweet-tasting; even children can drink it, it is cheap, and easy for people to accept. Nosebleeds, blood in the urine — all heat conditions, all applicable. I believe every person will meet a heat condition in life; when you do, think of bai mao gen, buy some at the pharmacy, soak it and drink it as tea. When the heat toxin is resolved, you will remember — Doctor Zhang Xichun once summarized this for us.

Spending a little time each day talking about this — it is so that Doctor Zhang Xichun’s experience becomes more widely known. Listen, grasp this knowledge, and if one day it protects you and relieves your pain, that is a very good thing.

What to take away

1. A rash must be transmitted outward, never suppressed. If you push a rash back, the poison can attack the heart; a rash that comes out smoothly is the favorable, healing course.
2. Fever that stays after the rash erupts, with restless agitation and a weak pulse, points to latent heat transforming in a yin-deficient body — here the pathogen had entered shaoyin and broken the heart-kidney communication, so restlessness dominated.
3. White Tiger plus Ginseng is Doctor Zhang’s standard for qi-level heat with insufficient upright qi — raw gypsum clears the heat, codonopsis supports the upright qi; here he also added fresh cogongrass root to transmit the rash toxin outward.
4. Bai mao gen (cogongrass root) is a humble wild grass with three great skills: it drains heat toxin through the urine, clears lung heat, and — most importantly — transmits the latent heat of the viscera outward and pushes rash toxin to the surface. It is gentle, sweet, cheap, and safe even for children.
5. Even the greatest formula can fail — and a famous doctor stays flexible. The White Tiger plus Ginseng failed twice in this case, and six liang of fresh bai mao gen, drunk hot in two doses, cured it completely. When the spleen-stomach is injured by cold-cooling medicine, stop the cold medicine and change course.

Arranged from Doctor Luo Dalun’s lecture on Doctor Zhang Xichun’s cases; the case is from the Records of Chinese Medicine with Western Reference (《医学衷中参西录》).