Hou Zao (Macaque Bezoar)

Chinese Herb Actions

Chinese Herb Dosage

• What is the dosage of Hou Zao (macaque bezoar)?

  No dosage is published on this page. Hou Zao is a primate-derived material that is largely obsolete, is not carried by mainstream herbal pharmacies, and cannot be sourced without the wildlife-trade and animal-welfare problems described below. Publishing a figure would imply that the substance is appropriately obtainable and usable, which is not our position.

  Historic materia medica did record small quantities, as is typical for costly animal concretions used in pill and powder form rather than in bulk decoction. We deliberately do not reproduce those figures here. Readers studying classical texts for scholarship or examinations should treat the entry as historical.

  Source: editorial policy for endangered- and primate-derived materials on this site, consistent with our other historical animal-derived entries. Reference statement only.

Chinese Herb Contraindications & Cautions

• Are there cautions for Hou Zao, and what is the conservation and welfare position?

  The main cautions attached to this entry are not pharmacological but ethical, legal and practical: it is a primate-derived material, macaques are covered by the international endangered-species trade convention, and no cultured or synthetic version exists. The classical contraindications recorded on this site are that it was not to be used where there was no heat from excess, or where the phlegm pattern was cold rather than hot — recorded here for completeness of the historical entry only.

  • Primate sourcing. A bezoar cannot be collected from a living animal without invasive intervention; in practice these concretions are recovered from dead animals. That is an unavoidable welfare issue rather than an incidental one.
  • Conservation status has deteriorated, not improved. The long-tailed macaque (Macaca fascicularis), once among the most widespread primates in Asia, was elevated to Endangered on the IUCN Red List in 2022, with removal from the wild for scientific, commercial and recreational purposes identified as a driver alongside habitat loss, inadequate regulation and culling in human–macaque conflict. Species within the genus differ in status, but the direction of travel across Asian macaque populations is downward.
  • Identity and adulteration. Animal concretions are high-value, low-volume goods, and the analytical literature on the better-studied ox gallstone documents deliberate contamination and undeclared additives. There is no comparable published authentication method for macaque bezoar, so material offered under this name cannot be verified.
  • General animal-derived caution. As with any raw animal material, microbiological quality is unverified and there is no pharmacopoeial standard behind it.

  Sources: our own site record of the classical contraindications (not for cases without heat from excess; not for cold-phlegm); PMID 37667504, DOI 10.1002/ajp.23547 (long-tailed macaque elevated to Endangered on the IUCN Red List in 2022; drivers of decline); PMID 36871364, DOI 10.1016/j.jpba.2023.115320 (adulteration documented for the analogous ox gallstone); international endangered-species trade convention coverage of macaques, cross-referenced against multiple online sources. Neutral reference facts; not medical advice.

Chinese Herb Toxicity & Overdose

• None Noted

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 Hou Zao (Calculus Macacae Mulattae)?

  No — a literature search of PubMed and PMC returns no pharmacological, chemical or clinical studies of macaque bezoar as a medicinal material. We state that plainly rather than fill the section: there is no research base to summarise, and asserting one would be inaccurate.

  Where the relevant modern literature does exist is in two adjacent areas:

  • The analogous ox gallstone. Calculus Bovis has a real analytical literature, driven by the need to tell natural, in-vitro cultured and artificial material apart and to detect adulteration — quantitative NMR profiling with principal component analysis, and UHPLC-Q/TOF mass spectrometry, have both been applied to that problem. This is the model for how a valuable animal concretion gets standardised and, in part, replaced.
  • Macaque conservation. The primatology literature documents the decline of Asian macaques, including the 2022 reassessment of the long-tailed macaque as Endangered and the subsequent petition for United States Endangered Species Act protection.

  The absence of a research base is itself the substantive finding for this entry, and is consistent with the material being obsolete.

  Sources: PubMed and PMC searches for macaque bezoar and Calculus Macacae returned no studies of the material (searched 2026); PMID 36871364, DOI 10.1016/j.jpba.2023.115320; PMID 31825798, DOI 10.1016/j.jpba.2019.112979; PMID 37667504, DOI 10.1002/ajp.23547. Research context, not a therapeutic claim.

Chinese Herb Notes

• How does Hou Zao compare with Niu Huang (ox gallstone)?

  The two are closely analogous: both are animal gallstones or concretions, both are cold, both clear heat and transform phlegm, and both were reserved for acute, serious presentations with clouded consciousness or convulsion — but Niu Huang is the one that survived into modern practice, and Hou Zao is the one that did not. Niu Huang (Calculus Bovis, ox or cattle gallstone) is the defining ingredient of An Gong Niu Huang Wan and one of the classical cooling orifice-openers; Hou Zao occupied a narrower niche in the phlegm-heat category.

  • Shared logic — both were understood as concretions formed in a large mammal, both are cold and bitter, and both were described as clearing heat, transforming phlegm and settling convulsions.
  • Where they differ in the classical description — Niu Huang is recorded on this site as entering the Heart and Liver and is grouped with the substances that open the orifices and awaken the spirit; Hou Zao is grouped with the herbs that cool and transform phlegm-heat, with an additional recorded role in softening scrofula and nodules.
  • The decisive practical difference is supply — natural ox gallstone is rare and costly, so in-vitro cultured and artificial forms of Calculus Bovis were developed and are recognised alongside the natural material, as our own Niu Huang entry records. Analytical chemistry papers now routinely distinguish natural, in-vitro cultured and artificial Calculus Bovis by mass spectrometry and by quantitative NMR profiling, and the same techniques are used to expose deliberate adulteration. No comparable cultured or synthetic pathway exists for macaque bezoar.

  That contrast is the useful lesson of this entry: where a substitution route existed, it was taken and standardised; where it did not, the material simply fell out of use.

  Flags in our own records, left unchanged for the site editor. (1) The tone-marked pinyin on our Hou Zao record reads “hóu zăi,” which does not match the romanisation “Hou Zao” used for the entry itself; we have flagged this rather than edited it. (2) Our record marks Hou Zao as not toxic or endangered, which does not reflect the protected status of macaques; also flagged, not changed.

  Sources: our own site identity records for Hou Zao and Niu Huang, and our Niu Huang entry on natural, in-vitro cultured and artificial Calculus Bovis; PMID 36871364, DOI 10.1016/j.jpba.2023.115320 (quantitative NMR profiling distinguishing natural, in-vitro cultured and artificial Calculus bovis, and detecting undeclared adulterants); PMID 31825798, DOI 10.1016/j.jpba.2019.112979 (UHPLC-Q/TOF-MS with principal component analysis distinguishing the three forms). Historical and comparative reference.