Traditionally used for
- Eye health
- Nose & throat
- Cough & breathing
- Skin
Cautions & contraindications
- Pregnancy
- Breastfeeding
- Young children
- Kidney conditions
- Toxic — professional use only
☯ TCM Properties
Clears Heat and Resolves Toxicity; Promotes Tissue Regeneration and Heals Sores; Clears Lung Heat and Transforms Phlegm; Brightens the Eyes and Removes Visual Obstructions
Traditional Chinese Uses
Peng Sha (borax) is a cool mineral substance used in Chinese medicine primarily as a topical remedy for sore throats, oral ulcers, oral thrush, and eye inflammation. It clears Heat toxin and resolves Phlegm when applied externally to the mouth and throat. While classical texts described small internal doses for Lung Phlegm, modern practice predominantly favors external application given safety considerations regarding oral ingestion. It remains an important topical agent in Chinese medical formulas for oropharyngeal conditions.
Relationships
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Botanical Description
Peng Sha is sodium tetraborate decahydrate (Na2B4O7·10H2O), the naturally occurring mineral borax, historically mined from evaporite deposits of dry lake beds in Tibet, Qinghai and Xinjiang. The crude mineral occurs as colourless to white prismatic monoclinic crystals or as compact white to greyish granular masses with a vitreous to dull lustre, soft (Mohs 2-2.5) and soluble in water to yield a mildly alkaline solution with a sweetish, faintly alkaline taste. For medicinal use the crude mineral is recrystallised from hot water and dried to give a clean, white, friable crystalline powder. On heating it loses water of crystallisation, swelling first into a porous white mass and then fusing to a clear glass — a property formerly exploited in metallurgy and glazing.
Active Constituents
Sodium tetraborate decahydrate (borax)
Hydrated sodium borate mineral (borax/tincal group)Concentration: Refined pharmaceutical Peng Sha is assayed for Na2B4O7·10H2O content, reported as 99.0-103.0 percent in the Chinese Pharmacopoeia monograph. The pure decahydrate is 11.3 percent boron by mass, so the classical 1.5-3 g oral dose delivers roughly 170-340 mg elemental boron.
This is the whole drug, and it is also the whole toxicological entity: everything recorded below about boron applies to it. In the concentrations used on mucosa it is a weakly alkaline buffering salt with bacteriostatic and fungistatic activity, which is the rational basis of the throat, mouth and eye applications; it has no other established pharmacology.
Boric acid
Boron oxyacid formed on hydrolysis of borax in water and gastric acidConcentration: Borax hydrolyses on dissolution; at gastric and plasma pH boron is present essentially entirely as undissociated boric acid, B(OH)3
Boric acid is the species actually absorbed, distributed and renally excreted, so borax and boric acid share one toxicological profile and one regulatory limit. EFSA set a group ADI of 0.16 mg boron/kg body weight/day for boric acid (E 284) and borax (E 285), from a rat developmental NOAEL of 9.6 mg boron/kg/day with a 60-fold uncertainty factor. A single 1.5 g dose of Peng Sha therefore supplies roughly eighteen times the whole-day ADI for a 60 kg adult.
Tincal ore gangue: calcite, dolomite, clays, ulexite and colemanite
Carbonate, silicate and accessory borate minerals of the crude playa evaporite oreConcentration: Variable in crude tincal; removed by dissolution and recrystallisation to the assayed pharmaceutical grade
Not therapeutically active. Its significance is that crude mined tincal and refined pharmacopoeial borax are different articles, and only the refined salt has an assay behind it; unrefined material bought as a mineral rather than as a drug is not the article the monograph describes.
Arsenic, lead, cadmium and mercury (trace)
Trace heavy-metal and metalloid contaminants of the mineralConcentration: No element-specific As, Pb, Cd or Hg limit for Peng Sha could be verified in the pharmacopoeial text; the monograph is controlled by a purity assay for Na2B4O7·10H2O rather than by elemental limits. The Chinese Pharmacopoeia figures usually quoted for Chinese medicines - Pb 5, Cd 1, As 2, Hg 0.2 and Cu 20 mg/kg under general chapter 2321 - are written for designated herbal pieces and are not applied to purified mineral salts of this kind.
Recrystallised borax is a chemically simple salt and is not a notable heavy-metal carrier, unlike the sulfide- and zinc-ore minerals in this class. The practical point is negative and should be stated as such: the absence of an assay is not evidence of absence, and a batch sold as mineral tincal rather than as pharmaceutical borax carries no elemental guarantee at all.
⚠ Drug Interactions
Boric acid and other borate-containing products (eye washes, antiseptic and dusting powders, vaginal boric acid capsules, borate insecticidal baits)
Borax and boric acid are the same toxicological entity once absorbed, and regulators treat them under a single group ADI (EFSA, 0.16 mg boron/kg bw/day). Body burden is additive across oral, mucosal, vaginal and damaged-skin routes, and boron is cleared almost entirely by the kidney, so concurrent sources stack. Intravaginal boric acid is in routine gynaecological use for azole-resistant and non-albicans candidiasis, which makes co-exposure a realistic scenario rather than a theoretical one.
Clinical note: Take a deliberate history of every borate source - eye drops and washes, vaginal capsules, antiseptic powders, ant baits - before prescribing Peng Sha internally, and do not add an internal borate to a patient already using one.
Borax used illegally as a food additive (noodles, rice cakes, fish and meat balls, dumpling wrappers)
Borax and boric acid are prohibited as food additives in China and appear on the 2008 Ministry of Health list of non-food substances illegally added to food (first batch); they are excluded from the permitted additive list GB 2760. In the EU boric acid (E 284) and borax (E 285) are authorised only as preservatives of sturgeon eggs, up to 4 g boric acid/kg. Illegal use to firm the texture of starch and meat products nevertheless persists and is enforced against, so a patient's dietary boron intake may be well above the food-survey estimates on which the ADI margin was calculated.
Clinical note: Do not treat the ADI margin as protective in populations where borax adulteration of staple foods is known; keep internal use short, intermittent and at the low end of the range, and prefer topical or buccal routes where the indication allows.
Topical or mucosal application to broken skin, burns, ulcerated mucosa or nappy-rash areas
Intact skin is a reasonably effective barrier to boron, but compromised skin is not. Hadrup and colleagues' review of boric acid, borax and other boron compounds records that skin exposure to boric acid has proven fatal in some cases, and that the classic modern poisonings are the improper use of boric-acid antiseptics in newborns and infants. Minimum lethal oral doses have been reported at 2-3 g in infants, 5-6 g in children and 15-20 g in adults - the adult figure sits within a factor of five to ten of the classical internal dose of the drug.
Clinical note: Never apply Peng Sha preparations to denuded skin, burns, weeping eczema or nappy rash, and never to infants at all by any route. Buccal and ophthalmic use in adults should be short-course and spat out rather than swallowed.
Pregnancy, breastfeeding and preconception care
The point of departure for every current boron limit is developmental, not systemic: EFSA's group ADI derives from a rat developmental toxicity study with a NOAEL of 9.6 mg boron/kg bw/day, and reproductive toxicity together with weight loss are the endpoints identified in animals across the review literature. Boron crosses the placenta and is excreted in milk. Chinese classical practice already lists Peng Sha as contraindicated in pregnancy and against long-term use.
Clinical note: Absolute contraindication in pregnancy, in women trying to conceive, and in lactation. This is not a caution to be weighed against benefit for a drug whose indications are all served by safer agents.
Renal impairment and concurrent nephrotoxic drugs (aminoglycosides, ciclosporin, high-dose NSAIDs)
Boron excretion occurs mainly via the urine, so glomerular filtration sets the clearance and any fall in it raises steady-state boron for a given intake. The kidney is also a target organ in lethal human boron ingestion, alongside liver, central nervous system, gastrointestinal tract and skin, which makes the interaction bidirectional.
Clinical note: Avoid internal Peng Sha in any degree of renal impairment and in patients on nephrotoxic drugs; there is no monitoring assay in routine clinical use to fall back on.
Cinnabar (Zhu Sha, mercuric sulfide) in the classical Bing Peng San formula
Bing Peng San, from Chen Shigong's Wai Ke Zheng Zong of 1617 and still the standard proprietary vehicle for Peng Sha in throat and mouth disease, combines borax with borneol, Xuan Ming Fen (mirabilite) and cinnabar. Cinnabar is mercuric sulfide; the powder therefore delivers two mineral toxicants to inflamed and often ulcerated oral mucosa, where absorption is greater than through intact epithelium. This is a formulation hazard, not a pharmacodynamic one, and it is easy to miss because the borax risk is the one usually discussed.
Clinical note: Read the label of any proprietary Bing Peng San before dispensing. Cumulative or repeated courses on ulcerated mucosa, and any use in children, should be avoided; cinnabar-free reformulations exist and should be preferred.
Dosage
| Form | Amount | Frequency | Duration | Population | Notes |
|---|---|---|---|---|---|
| topical | Appropriate amount — external use mainly | Daily | — | — | No ChP monograph in the 2020 一部. Borax (sodium tetraborate). Used chiefly externally as a wash or in throat/mouth powders. Borate is toxic on repeated ingestion — nausea, vomiting, dermatitis, renal injury, and it is a reproductive toxicant; internal use is not recommended and no internal dose is given here. |
Dui Yao — Herb Pairs
The classical two-herb combinations this herb appears in, each with an action neither herb has alone.
Applied topically, they clear heat, resolve toxicity, reduce swelling and relieve pain in the throat and mouth.
External use for sore swollen throat and mouth ulcers.
Core pair of a classical formula — Bing Peng San, Wai Ke Zheng Zong (Chen Shigong, 1617)
Evidence Tier
Limited evidence · 2 studiesRecorded studies by study design, strongest design at the top. This is a study-design tier only, not a GRADE rating: it does not weigh risk of bias, consistency or precision.
Systematic review / meta-analysis
0
Randomized controlled trial
0
Other clinical trial
1
1 verified · 0 unverified
Observational / case report
0
In vitro / animal
0
Other / unclassified
1
1 verified · 0 unverified
Verified: design read from PubMed for a DOI that resolves to the cited paper Unverified: taken from the study's recorded description
Clinical Studies
The effect of sodium tetraborate and alum in the management of acute childhood diarrhoea
A small preliminary controlled observation in Burma in which sodium tetraborate (borax) and alum, both long-standing traditional remedies, were given to 26 children with acute diarrhoea to see whether they reduced oral rehydration fluid requirements. The authors report an appreciable reduction in fluid requirement and no side effects detected in the 26 children. This is the only human trial of internal borax that could be located, and it is far too small and too weakly reported to establish either efficacy or safety; it is recorded here because it is what exists, and because it involves precisely the population - young children - in which boric acid and borax poisoning has historically been fatal.
Boric Acid for Recurrent Vulvovaginal Candidiasis: The Clinical Evidence
Systematic review of 14 studies (2 randomised trials, 9 case series, 4 case reports) of intravaginal boric acid, reporting mycological cure rates of 40-100 percent and vaginal burning in under 10 percent of cases, and concluding that boric acid is a reasonable option where azole-resistant or non-albicans Candida species are involved. It is included here not as evidence for Peng Sha but because it is the best-characterised human mucosal use of the borate ion: it shows the antifungal activity is real at mucosal concentrations, and it identifies a common concurrent borate source that must be counted against a patient's total boron load.
Historical Texts
Ri Hua Zi Ben Cao (Ri Hua Zi's Materia Medica)
Five Dynasties to early Song, around the 10th centuryBen Cao Yan Yi (Dilations upon Materia Medica), Kou Zongshi
Northern Song, 1116Ben Cao Gang Mu (Compendium of Materia Medica), Li Shizhen
Ming, 1596Wai Ke Zheng Zong (Orthodox Lineage of External Medicine), Chen Shigong, source of Bing Peng San
Ming, 1617References
- Hadrup N; Frederiksen M; Sharma AK. Toxicity of boric acid, borax and other boron containing compounds: A review . Regulatory Toxicology and Pharmacology (2021) [DOI]
- EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS). Scientific Opinion on the re‐evaluation of boric acid (E 284) and sodium tetraborate (borax) (E 285) as food additives . EFSA Journal (2013) [DOI]
- Culver BD; Shen PT; Taylor TH; Lee-Feldstein A; Anton-Culver H; Strong PL. The relationship of blood- and urine-boron to boron exposure in borax-workers and usefulness of urine-boron as an exposure marker. . Environmental Health Perspectives (1994) [DOI]
- Inada I; Kiuchi F; Urushihara H. Comparison of Regulations for Arsenic and Heavy Metals in Herbal Medicines Using Pharmacopoeias of Nine Counties/Regions . Therapeutic Innovation & Regulatory Science (2023) [DOI]
This information is for educational purposes only and is not intended to replace professional medical advice. Always consult a qualified healthcare provider before using any herbal remedy, especially if you are pregnant, nursing, or taking medications.
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