Fu Long Gan (Ignited Yellow Earth)

Chinese Herb Actions

Chinese Herb Dosage

• What is the dosage of Fu Long Gan (Zao Xin Tu), and how is it prepared?

  As a standalone decoction herb, roughly 15–30 g is typical; as the base for Huang Tu Tang it is used at a higher dose (commonly 30–60 g, with some sources going to 90–120 g) and decocted separately first. Because it is a friable, gritty earth/mineral, it is traditionally wrapped in a cloth or cheesecloth bag before decocting to keep sediment out of the liquid.

  Distinctive preparation: in its signature formula, Huang Tu Tang, Fu Long Gan is decocted alone for roughly 20–40 minutes, then the liquid is strained off and used as the water to cook the formula’s remaining six herbs — it is not simply added to the pot with everything else. When stove earth is unavailable, Chi Shi Zhi (Halloysitum Rubrum) is a recognized substitute, used at about 3–4 times the Fu Long Gan dose.

  Source: Sacred Lotus, Huang Tu Tang formula content; cross-checked against materia medica consensus. Reference only — not a prescription.

Chinese Herb Contraindications & Cautions

• Are there cautions for Fu Long Gan (Zao Xin Tu)?

  Fu Long Gan is a warming herb built for bleeding or vomiting from cold and deficiency; it is not appropriate for bleeding or vomiting from heat or yin deficiency. Bright-red or forceful bleeding, or nausea/vomiting with a red tongue, thirst, or other heat signs, calls for a cooling approach instead — using a warming astringent like Fu Long Gan in that context would aggravate the underlying heat.

  • Pattern fit — classical sources also treat it as unsuited to diarrhea from damp-heat, since its warming, astringing action can trap a heat pathogen rather than resolve it.
  • Sourcing/availability — genuine aged stove earth from traditional wood- or straw-fired clay stoves has become scarce as such stoves have largely disappeared from modern life; in current practice Chi Shi Zhi is the accepted substitute (see Notes). This is a practical sourcing note, not a safety instruction.
  • Any unexplained or persistent bleeding — gastrointestinal, uterine, or otherwise — warrants prompt medical evaluation; this herb is traditional-use reference material, not a substitute for that workup.

  Source: materia medica consensus (Bensky & Barolet; Chen & Chen), cross-checked against multiple TCM reference sites and the Sacred Lotus’s Huang Tu Tang cautions field. Traditional-use framing; not medical advice.

Chinese Herb Toxicity & Overdose

• Classically recorded as non-toxic. Historical materia medica (including the Ming-dynasty Ben Cao Gang Mu) records Fu Long Gan as acrid, slightly warm, and non-toxic, and modern materia medica references report no significant toxicity at traditional doses. As with any earth/mineral substance, genuine sourcing matters more than intrinsic toxicity risk: authentic material comes from long-fired, wood- or straw-burning clay stoves, and its practical scarcity today (rather than any documented toxicity) is the main reason Chi Shi Zhi is now the more commonly used substitute.

  Source: materia medica consensus, cross-checked across multiple TCM references. Reference note, not a safety guarantee.

Herb-Drug Interactions

• No well-established clinical herb–drug interactions are documented for Fu Long Gan. Some contemporary references raise a theoretical, unverified concern that, as a clay/mineral substance, it could physically adsorb co-administered oral medications or mildly buffer stomach acidity in a way that affects drugs sensitive to gastric pH (e.g., certain antifungals, iron supplements) — this is precautionary reasoning from its physical composition, not a demonstrated clinical interaction. (Flagged for practitioner confirmation; separating dosing times is the usual precaution for adsorptive mineral substances generally.)

Western / Biomedical Research

Chinese Herb Clinical Studies & Research

Provided as research context — a summary of published biomedical study, not a therapeutic or medical claim.

• Is there modern research on Fu Long Gan (Terra Flava Usta)?

  Limited, and almost entirely preclinical. Fu Long Gan is a rarely studied folk mineral substance; the one substantive recent study is a 2025 mouse experiment on its effect on gut bacteria, and there is no clinical trial evidence for its traditional bleeding or antiemetic uses in humans.

  • Gut microbiota modulation (preclinical) — a controlled mouse study compared dietary supplementation with Terra Flava Usta (Zaoxintu) against Gypsum Fibrosum (Shigao) and a control diet over 4 weeks. Both mineral medicines significantly altered gut microbiota composition and promoted certain beneficial bacteria (e.g., Faecalibaculum, Ileibacterium), each through distinct mechanisms; gut bacteria were observed forming biofilm structures specifically on the Terra Flava Usta surface. The authors frame both substances as candidate prebiotic materials, not as treatments for any diagnosed condition.

  Beyond this, modern pharmacology work involving Fu Long Gan is mostly folded into research on the compound formula Huang Tu Tang (Huangtu decoction) rather than the single herb — see that formula’s own research content. Direct clinical evidence for Fu Long Gan’s traditional hemostatic and antiemetic uses remains unverified.

  Sources: PMID 40232599, DOI 10.1007/s11655-025-4129-x (Chinese Journal of Integrative Medicine, 2025, mouse gut-microbiota study). Research context, not a therapeutic claim.

Chinese Herb Notes

• How is Fu Long Gan different from Chi Shi Zhi, Pao Jiang, and Ai Ye?

  All four warm and stop cold-deficiency bleeding, but Fu Long Gan is distinguished by its combined bleeding- and vomiting-stopping action — and, with Chi Shi Zhi, it is one of the two mineral/earth substances in this comparison, the other two (Pao Jiang and Ai Ye) being plant material. Choosing among them depends on which organ and which symptom (bleeding, vomiting, pain, or uterine cold) predominates.

  • vs Chi Shi Zhi — both are mineral/earth substances that warm the Middle Burner; Chi Shi Zhi is more astringent and stronger for chronic diarrhea (it also enters the Large Intestine), while Fu Long Gan has the broader range, including a more pronounced antiemetic action. The two are considered interchangeable in a pinch, which is why Chi Shi Zhi is the standard substitute when stove earth is unavailable.
  • vs Pao Jiang (blast-fried ginger) — both warm the Middle Burner and stop deficiency-cold bleeding; Pao Jiang is better at dispersing cold and relieving cold abdominal pain, while Fu Long Gan is more specifically indicated for stopping vomiting.
  • vs Ai Ye — both warm and stop cold-deficiency bleeding, but Ai Ye enters the Liver and Kidney channels and is the herb of choice for warming the uterus and menstrual/uterine bleeding, while Fu Long Gan centers on the Spleen and Stomach — gastrointestinal bleeding and vomiting.

  Key combination: Fu Long Gan is the chief herb of Huang Tu Tang (Jin Gui Yao Lue), paired with Fu Zi and Bai Zhu to warm and rebuild Spleen yang, and balanced against the cooling, nourishing Sheng Di Huang, E Jiao, and Huang Qin so the warming herbs don’t themselves drive heat into the blood. (Traditional formula context, not treatment advice.)

  Discrepancy note: the previous description on this record (and this site’s own record) states that Fu Long Gan “comes from the middle of the ashes from a stove where Zi Cao has been burned.” Multiple materia medica sources instead describe the source material as aged clay from the base/center of a traditional earthen cooking stove that has been fired for years by burning ordinary firewood or straw — not the unrelated herb Zi Cao (Lithospermi/Arnebiae Radix, a purple dye-root with no connection to stove construction). We believe the “Zi Cao” wording is a longstanding transcription error (plausibly a mix-up between chái cǎo “firewood/kindling” and the similarly written but unrelated zǐ cǎo, “Zi Cao”) and have corrected the description above; flagging for owner confirmation since it also appears on the live site.

  Source: materia medica consensus (Bensky & Barolet; Chen & Chen), cross-checked against multiple TCM reference sites; Sacred Lotus formula link.