Zao Xin Tu
Quick Facts
- What it is: Zao Xin Tu is baked earth taken from the floor of an old wood-fired stove and used in Chinese medicine for vomiting, diarrhoea and bleeding.
- Main uses: Vomiting and nausea (feeling sick), Long-running diarrhoea, Blood in the stool, Heavy womb bleeding
- Best for: Nothing has been proven in people; all listed uses rest on tradition alone
- Active ingredients: Clay and silica (the mineral part of soil), Iron oxide (rust), Calcium and magnesium salts, Potash salts from wood ash, Possible lead, arsenic and cadmium (toxic metals), unmeasured
- Forms: Hard lumps of baked earth, Loose powder, Cloudy tea, settled and strained, Part of the old formula Huang Tu Tang
- Time to effect: Old texts speak of a few days; no trial has ever measured it.
- Side effects: Constipation and gut upset are the common ones; the bigger risk is toxic metals in untested soil.
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What is Zao Xin Tu?
Zao Xin Tu is baked earth. It is dug from the floor of an old wood-fired stove, where years of heat have dried and hardened it. Chinese medicine gave it to calm a sick stomach and to slow bleeding.
It is a single drug, not a blend. Old books cooked it together with other herbs. The best known of those blends is Huang Tu Tang, or Yellow Earth Decoction.
No human trial has tested it. Long use in one tradition is not proof that a thing works, and that point holds for every claim on this page.
Because it is plain soil, it may hold lead or other toxic metals. For that reason we grade it as a caution, not a routine remedy.
How does Zao Xin Tu work?
No one has shown how it works in the body. There is no study that tracks what it does once you swallow it.
In Chinese medicine the idea was that stove earth is warm and drying. It was said to warm the middle, settle a stomach that is rising up, and hold blood in place. That is a way of talking about symptoms, not a lab finding.
One plain guess is that clay soaks up water and acid in the gut, the way clay does in a jar. That guess has not been tested for this drug. Treat it as an idea, not a fact.
What forms does Zao Xin Tu come in?
You may meet it in three forms:
Lumps of hard red-brown baked earth, broken off the stove floor. Loose powder, ground from those lumps. A cloudy tea, made by boiling the earth in water.
The old way was to boil the earth first, let the grit sink, then use the clear water to cook the other herbs. Some books wrap the powder in cloth inside the pot instead.
It is rare in shops today. Most kitchens now use gas or power, so there are few old stoves left. Sellers often swap in Chi Shi Zhi (a red clay) or leave it out of the blend.
Where it comes from:
Stove earth has a long record in Chinese medicine under the name Fu Long Gan. It is listed in the Ming Yi Bie Lu, a drug book from about 500 CE.
It is best known from Huang Tu Tang (Yellow Earth Decoction). That formula is in the Jin Gui Yao Lue, written by Zhang Zhongjing around 200 CE, and was given for blood in the stool.
So it is a long-standing staple of one tradition. It has no record in Western herbal use.
Who should avoid Zao Xin Tu?
- Do not use if you are pregnant: soil may hold lead, which harms an unborn baby even in tiny amounts.
- Do not use if you are breastfeeding, because lead and other metals pass into breast milk.
- Never give it to a child or a teenager, for any reason.
- Do not use if you are trying to get pregnant.
- Do not use if you have kidney disease, since damaged kidneys clear metals poorly.
- Do not use if you have anaemia (low blood iron) or a known raised lead level.
- Do not use if you have constipation, a blocked bowel, or a bowel narrowed by disease or surgery.
- Do not use if you are bleeding from anywhere and the cause has not been found by a doctor.
- Do not use if you take a blood thinner such as warfarin, apixaban, aspirin or clopidogrel.
- Do not use if you take thyroid tablets, tetracycline or quinolone antibiotics, unless a doctor has agreed a plan.
- Do not use earth of unknown source, and never dig it yourself from a stove, fireplace or barbecue.
When should you see a doctor?
See a doctor the same day if you are vomiting and cannot keep fluids down, or if you feel faint, dizzy or very weak.
Go to an emergency department if you vomit blood, pass black tarry stools, pass a lot of fresh blood, or have severe belly pain.
Book an appointment soon if you have bleeding between periods, bleeding after the menopause, diarrhoea lasting more than a week, or blood on the toilet paper.
Ask for a blood lead test if you have taken stove earth or any mineral remedy for weeks and feel tired, foggy, or have belly pain and headaches that will not shift.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
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