Qing Fen (Calomel)

Chinese Herb Actions

Chinese Herb Contraindications & Cautions

• Are there cautions or restrictions on Qing Fen (calomel)?

  Qing Fen is a toxic mercury compound, and traditional materia medica sources restrict it to careful external application only, with internal use avoided in contemporary practice. It is contraindicated in pregnancy and in individuals who are constitutionally weak or deficient or who have kidney or liver disease, and it is not applied to broken, inflamed, or hypersensitive skin, or used for prolonged periods.

  • Pregnancy — contraindicated in traditional sources.
  • Deficient constitution, kidney or liver disease — contraindicated per traditional sources, consistent with mercury’s documented nephrotoxicity (see Toxicity).
  • Not for prolonged or large-area external application — traditional cautions specifically warn against overdose and extended use, reflecting cumulative toxicity risk.
  • Obsolete in contemporary clinical practice — modern TCM references describe Qing Fen as an obsolete or restricted substance; it is not part of routine practice in licensed clinics today, and outside a licensed, regulated setting it should not be used at all.

  Source: multiple online sources (Calomelas / Qing Fen); Frontiers in Pharmacology (2022), DOI 10.3389/fphar.2022.807807. Reference safety information, not a description of use.

Chinese Herb Toxicity & Overdose

• High — Qing Fen is mercurous chloride (Hg₂Cl₂), a mercury compound, and both historical and modern case reports document mercury poisoning linked to calomel exposure. Calomel is photolabile: prolonged light or heat exposure causes it to decompose into more toxic mercuric chloride and metallic mercury. Once absorbed, inorganic mercury concentrates heavily in the kidney — primarily the proximal tubule — where it produces injury through oxidative stress and inhibition of sulfhydryl-group-dependent enzymes; neuropsychiatric, dermatologic, and renal effects are the most consistently reported signs of overexposure.

  Documented history and case evidence:

  • Acrodynia (“pink disease”) — chronic mercury exposure from calomel-containing teething powders caused epidemics of this syndrome (pink/dusky discoloration, swelling, paresthesia, and desquamation of the hands and feet) in infants during the early-to-mid 20th century; the link to mercury was established by the 1940s and calomel was subsequently removed from teething products in Europe and North America. A 2003 case report describes 20-month-old twins poisoned by a calomel-containing teething powder obtained from India, requiring chelation therapy — illustrating that such products can still reach households outside the regions where they were banned.
  • Chinese patent-medicine mercurials — a 1992 toxicology review identified calomel (mercurous chloride) and cinnabar (mercuric sulfide) as the two mercury compounds intentionally present in a number of Chinese patent medicines sold in North America, and recommended screening for mercury toxicity in patients using these products. A related 2000 review of unregulated “potions” documented mercury poisoning from calomel-containing beauty creams and cited a separate case series of three patients with inorganic mercury poisoning traced to Chinese herbal preparations and salves.
  • Clinical case report — an 80-year-old patient using a Chinese herbal preparation for rheumatism developed acute generalized dermatitis and abnormal liver function with an elevated blood mercury level; levels normalized after the herbal product was stopped, with diet unchanged, supporting the herbal product as the source.
  • Modern skin-cream contamination — a 2015 review of mercury toxicity from calomel-adulterated skin creams found products containing 28,000–210,000 ppm mercury (versus a 1 ppm FDA cosmetic limit), with cream users showing urinary mercury of 37–482 µg/g creatinine and household surfaces (bedding, clothing, cream jars) contaminated with mercury vapor; reported symptoms included weakness, tremor, hypertension, irritability, sleep disturbance, and cognitive impairment, including in non-users living in contaminated households.

  Sources: PMID 12538551 (CMAJ, 2003, calomel teething-powder poisoning case, twins); PMID 1609495 (Veterinary and Human Toxicology, 1992, calomel and cinnabar in Chinese patent medicines); PMID 10903282 (Western Journal of Medicine, 2000, mercury poisoning from unregulated potions); PMID 26364641 (International Journal of Environmental Research and Public Health, 2015, mercury toxicity from calomel-adulterated skin creams); British Columbia Medical Journal case letter, “Mercury and Chinese herbal medicine.” Reference safety information, not a description of use.

• This herb is considered toxic.
  (while some Chinese herbs are toxic, it must be noted that many come prepared, or are combined, to mitigate their toxicity)

Herb-Drug Interactions

• No established clinical drug-interaction studies exist for calomel specifically, as it is not an ingredient in contemporary licensed pharmaceutical or TCM clinical practice. As a general toxicological point rather than a documented interaction: mercury body burden is cumulative and additive across exposure sources, so concurrent exposure to other mercury-containing products (other mercurial patent medicines, mercury-containing skin-lightening creams, dietary methylmercury) would be expected to add to total mercury load, and any nephrotoxic medication would be expected to compound the kidney risk described under Toxicity. These are general toxicology inferences, not clinical interaction data, and are flagged for reference only.

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 calomel (Qing Fen) and mercury safety?

  Yes — modern research on calomel is almost entirely toxicological and regulatory rather than therapeutic, documenting mercury-poisoning cases and informing restriction rather than supporting continued use. No clinical trials support therapeutic use; the literature is case reports, toxicology reviews, and regulatory/consumer-safety guidance.

  • TCM pharmacology/toxicology review (2022) — a Frontiers in Pharmacology review of mercury-containing TCM preparations describes calomel as restricted to external-only application (“toxic and should not be taken orally”), summarizes comparative kidney-toxicity data across mercury compounds, and notes that mineral drugs such as realgar and cinnabar have been removed from some patent-medicine formulations to meet modern safety requirements.
  • Chinese patent-medicine mercury survey (1992) — identified calomel and cinnabar as the two mercurials found in patent medicines circulating in North America and called for clinician awareness when screening patients using these products.
  • Unregulated-product mercury poisoning review (2000) — documented ongoing mercury poisoning from calomel-containing beauty creams and Chinese herbal preparations obtained outside regulated retail channels.
  • Adulterated skin-cream toxicity study (2015) — quantified mercury concentrations, urinary mercury levels, and household contamination from calomel-adulterated skin creams, with neuropsychiatric symptoms as the most sensitive indicator of exposure.
  • Historical acrodynia case report (2003) — documents that calomel-containing products, though banned for decades in North America, can still reach households through informal/imported channels, with pediatric poisoning requiring chelation therapy.
  • Regulatory guidance — the U.S. FDA lists “mercurous chloride” and “calomel” among label terms indicating mercury content in cosmetics and skin-lightening products, which are illegal to sell over the counter in the United States; the FDA cosmetic mercury limit is 1 ppm.

  Sources: DOI 10.3389/fphar.2022.807807 (Frontiers in Pharmacology, 2022); PMID 1609495 (Veterinary and Human Toxicology, 1992); PMID 10903282 (Western Journal of Medicine, 2000); PMID 26364641 (International Journal of Environmental Research and Public Health, 2015); PMID 12538551 (CMAJ, 2003); U.S. FDA consumer guidance on mercury in skin products. Research context, not a therapeutic claim.

Chinese Herb Notes

• How is Qing Fen classified today, and how does it differ from other mercury-bearing minerals such as Zhu Sha (Cinnabar)?

  Qing Fen is one of at least two mercury-bearing mineral substances documented in the Chinese materia medica — the other being Zhu Sha (Cinnabar, mercuric sulfide) — and modern sources describe it as an obsolete or heavily restricted substance rather than one in routine contemporary use.

  • Different mercury compound — Qing Fen is mercurous chloride (Hg₂Cl₂, traditionally sublimed from mercury, alum, and salt); Zhu Sha/Cinnabar is mercuric sulfide (HgS). Comparative toxicology research finds different mercury compounds carry substantially different toxicity profiles despite sharing the same element (see Research).
  • Shared regulatory trajectory — a 2022 pharmacology review reports that mineral drugs including realgar and cinnabar have been removed from some Chinese patent-medicine formulations to meet modern export and safety requirements; calomel is described in the same literature as restricted to strict external-only application.
  • Public-health relevance today — calomel/mercurous chloride is not an ingredient in contemporary licensed TCM clinical practice, but it persists as an unauthorized ingredient in some imported skin-lightening and other unregulated topical products (see Toxicity). U.S. FDA consumer guidance instructs shoppers to check cosmetic labels for the words “calomel” or “mercurous chloride” and to stop use immediately if found.

  Note: Traditional-source details vary — some materia medica references list the Large Intestine and Small Intestine channels with a “cold” nature, while others cite Large Intestine, Kidney, Liver, and Bladder with a “very cold” nature. This site’s own record (channels: Bladder, Kidney, Liver; properties: Spicy, Cold, Toxic) is left unchanged pending owner review, since this may reflect genuine variation between historical/regional materia medica traditions rather than an error.

  Source: multiple online sources (Calomelas / Qing Fen); Frontiers in Pharmacology (2022), DOI 10.3389/fphar.2022.807807; U.S. FDA consumer guidance on mercury in skin products.

This herb is toxic or restricted in the United States