Borax (Sodium Tetraborate)

Borax is the common name for sodium tetraborate decahydrate, a soft white mineral salt that has sat on hardware and laundry shelves for well over a century. It is mined, not synthesised — pulled out of dried lake beds and evaporite deposits — and it has an unusually wide range of genuine uses: it softens water, buffers pH, kills fungi and insects, preserves timber, and slows the spread of fire in treated cellulose.

It also sits at the centre of one of the most persistent pieces of health folklore on the internet: the claim that borax is a suppressed cure for arthritis, and that its disappearance from American medicine cabinets was the result of a regulatory conspiracy rather than a safety finding. That story is worth taking seriously enough to check, because the chemistry underneath it is not nonsense — boron really is biologically active, and the research on boron and joint health really does exist. What does not survive checking is the conspiracy framing built on top of it, and the leap from boron the trace nutrient to borax the household compound.

This page covers what borax is, what it verifiably does around a house, what the regulatory record actually says, and where the popular claims about drinking it come from.

Table of Contents

  1. What Borax Actually Is
  2. Where It Comes From
  3. How It Actually Cleans
  4. What Borax Does Not Do
  5. Borax Is Not Boric Acid
  6. Household and Structural Uses
  7. Wood Preservation: What the USDA Found
  8. Boron the Nutrient vs Borax the Compound
  9. The Safety Record
  10. The "Borax Conspiracy" Claim
  11. Handling Borax Safely
  12. Key Research Papers
  13. Connections
  14. Featured Videos

What Borax Actually Is

Borax is Na2B4O7·10H2O — two sodium atoms, four boron atoms, seven oxygens, and ten water molecules locked into the crystal. Those ten waters matter more than they look. They are why borax is a soft, chalky powder rather than a hard salt, why it dissolves readily in hot water and sluggishly in cold, and why heating it makes it puff up and lose volume as the water is driven off.

Three properties do nearly all of the practical work:

  1. It is alkaline, but gently so. A borax solution settles at roughly pH 9. That is alkaline enough to help lift grease and to make soap work better, but far short of lye or washing soda. It will not burn skin on contact the way a strong caustic will.
  2. It is a buffer. Borate in water resists pH change. This is why borax is a laboratory standard for calibrating pH meters, and why in a wash it holds the water in the alkaline range even as dirt and soap residue try to drag it around.
  3. The borate ion binds things. Borate forms complexes with calcium and magnesium — the two ions that make water "hard" — and with a range of organic molecules containing paired hydroxyl groups, including many sugars.

By mass, borax is about 11% elemental boron. That single number governs everything on this page that concerns swallowing it, and it is the number most often left out of the discussion. One gram of borax carries roughly 113 mg of boron.

Where It Comes From

Most refined borate in the world comes from two places: Turkey, which holds the largest known reserves, and a single open-pit mine in California. That mine sits beside the town of Boron, about 100 miles north-east of Los Angeles, and supplies on the order of 30% of world demand for refined borates. It is the largest open-pit mine in California.

The "20 Mule Team" branding on the familiar box is not marketing invention. In the 1880s, before the Boron deposit was developed, borax was hauled out of Death Valley by teams of twenty animals pulling linked wagons roughly 165 miles to the railhead at Mojave. The operation lasted only about six years, but the image outlived it by a century and a half and is still on the carton.

The deposits themselves are evaporites — the residue of ancient lakes that dried up in volcanic terrain, concentrating borate carried in by hot springs. This is why borax is fairly described as a naturally occurring mineral. It is worth noting, though, that "naturally occurring" is a statement about origin, not about safety. Arsenic, lead and asbestos are all naturally occurring minerals too; see Toxic Minerals.

How It Actually Cleans

Borax's reputation as a laundry booster is earned, and the mechanisms are well understood.

Water softening

Hard water is water carrying dissolved calcium and magnesium. Those ions react with soap to form the insoluble scum that greys fabric and leaves film on glassware. Borate binds calcium and magnesium, taking them out of circulation so the soap can do its job. This is the same role phosphates used to play in detergent, and it is the single largest reason borax makes an ordinary detergent perform better in hard-water areas.

Alkalinity and grease

Fats and oils release from fabric far more readily in alkaline water. Borax raises and then holds the wash water near pH 9. The holding is the useful part: soil entering the water would otherwise pull the pH down as the cycle runs.

Antifungal and bacteriostatic action

Borate is genuinely hostile to fungi and to many bacteria — this is the basis of its use in timber preservation and in mould control, and it is why borax-treated cellulose does not rot. In a washing machine it is what addresses the musty smell that accumulates in towels and in the machine's own seals.

Dishwashers and the 2010 phosphate change

The observation that dishwasher detergent stopped working as well around 2010 is accurate and has a documented cause. Sixteen US states passed laws restricting phosphorus in automatic dishwasher detergent to 0.5%, down from levels as high as roughly 8.7%, effective 1 July 2010. Rather than run two formulations, manufacturers reformulated nationally. Phosphates had been doing the water-softening job, and the replacements were, at first, worse at it. Adding borax to a load restores softening capacity that the reformulation removed — the complaint and the fix are both real.

What Borax Does Not Do

One claim circulates so widely it deserves direct correction: borax does not convert into hydrogen peroxide when it dissolves, and it is not a bleach.

The confusion is between two different compounds with similar names:

Whites do come out looking better with borax in the wash, but the reason is the water softening and the alkalinity — removing the mineral scum and soap residue that dulls fabric — not oxidation of stains. The distinction matters if you are choosing a product: if you actually need bleaching action, borax will not supply it, and sodium percarbonate or sodium perborate will.

Borax Is Not Boric Acid

These two are routinely used interchangeably in household advice, and they are not interchangeable. Both deliver boron, and their biological effects converge once absorbed — the body handles both largely as borate — but they differ in ways that matter in practice.

Most of the documented cockroach and ant baiting research, and most of the recorded human poisoning cases, involve boric acid rather than borax. Advice that cites a boric-acid study to support a borax practice is not automatically wrong, but it is not the same claim, and the dose is not the same dose. When you see a specific figure quoted, check which compound it applies to.

Household and Structural Uses

The following uses are well supported by the chemistry above and by long practice. None of them involve swallowing anything.

Laundry

Roughly half a cup per load alongside ordinary detergent, most useful in hard-water areas and with older or heavily soiled fabrics. The benefit is largest where water hardness is high and close to nil where the household already has a water softener.

Stained ceramics and cookware

Borax is mildly abrasive and alkaline enough to lift tea and coffee tannins, while being soft enough not to scratch a glaze. A teaspoon in a mug of hot water, left twenty minutes, does the work without scrubbing.

Toilets, drains and general cleaning

A quarter cup left in a toilet bowl overnight lifts hard-water staining and deodorises. Half a cup down a kitchen drain followed by hot water reduces grease accumulation. Both work through alkalinity plus the antimicrobial action, and both are dramatically cheaper than the dedicated products they replace.

Insect baiting

Borate mixed with a sugar attractant is a slow-acting stomach poison for cockroaches and ants. The insects carry it back to the nest, which is what makes it more effective than a contact spray. Two cautions: most of the published efficacy data uses boric acid rather than borax, and the same properties that make a bait work make it hazardous to a curious toddler or pet. Bait placement — inside cabinets, behind appliances, in cracks — is not a detail, it is the safety control.

Mould control on hard surfaces

A borax solution on masonry, concrete block and bare subfloor raises surface pH and leaves a residue that fungi struggle to colonise. Unlike bleach, it is not consumed by contact with organic matter, so the residual effect persists. On porous surfaces it will also leach away if the surface gets repeatedly wet, so it is a preventive measure, not a cure for an active water problem.

Fire retardancy in cellulose

Borate compounds are the standard fire retardant in cellulose building insulation, which is why blown-in recycled newsprint meets fire codes at all. Treated cellulose chars rather than flaming, and releases water of hydration as it heats. This is real, established building science.

Weed control on hard surfaces

Borate is phytotoxic and will kill plants growing in driveway cracks and gravel. It is also persistent in soil and does not break down. Applying it anywhere near a lawn, a bed, or a vegetable garden can sterilise that ground for a long time, and there is no straightforward way to remove it once it is there. Runoff carries it further than the treated patch. Of all the uses on this page, this is the one most likely to cause lasting regret.

Wood Preservation: What the USDA Found

The claim that the US Forest Products Laboratory validated borax as a decades-long termite and decay treatment traces to real research, and it is worth reading precisely, because the popular retelling overstates it in two specific ways.

The paper usually cited is FPL-RP-655, Efficacy of a Borax–Copper Preservative in Exposed Applications, published by the Forest Products Laboratory in Madison, Wisconsin in 2009 by Stan Lebow and colleagues. The finding is genuine: borate is effective against decay fungi and termites, and has low toxicity to humans and the environment relative to the preservatives it competes with.

Two qualifications change the practical picture:

  1. The formulation tested was borax plus copper, pressure-treated. The tested preservative was roughly 7% copper hydroxide and 93% sodium tetraborate decahydrate, forced into southern pine sapwood under pressure. That is not the same as brushing a borax solution onto the surface of existing timber, and it should not be expected to perform the same.
  2. Borate does not bond to wood, and it leaches. This is the central, well-documented limitation of every borate wood treatment. Unlike preservatives that fix chemically to the timber, borate stays water-soluble and washes out wherever water reaches it. The copper in the tested formulation was there precisely to address exposed-application performance.

So: borate treatment of dry, protected interior timber — crawlspace joists, attic decking, sill plates that stay dry — is a legitimate, long-established practice with a real evidence base. A claimed "20 to 30 year" life applies only to timber that stays dry. In ground contact, in exposed applications, or anywhere water repeatedly wets the wood, a brush-applied borate treatment is temporary. If moisture is reaching the wood, that is the problem to fix first.

Boron the Nutrient vs Borax the Compound

Here is where household mineral and health claim meet, and where the arithmetic decides the argument.

Boron is biologically real. It influences calcium, magnesium and vitamin D metabolism, affects steroid hormone levels, and has measurable effects on bone. Nielsen's deprivation studies showed physiological consequences when boron intake was restricted and then restored. It is not classified as an essential nutrient for humans — no deficiency disease has been defined — but "not formally essential" is not the same as "does nothing," and the research is ongoing rather than closed. The site covers this in depth on Boron and Bone Density.

Typical dietary intake runs about 1–3 mg of boron per day in most populations, from fruit, nuts, legumes, leafy vegetables, coffee and wine. Prunes, raisins, almonds, avocados and chickpeas are among the densest ordinary sources.

The upper limits are published and are not in dispute:

Now apply the 11% figure. To reach the US upper limit of 20 mg of boron you need about 176 mg of borax — under a fifth of a gram. A level teaspoon of borax is roughly four to five grams, which carries on the order of 450–500 mg of boron: more than twenty times the adult upper limit in a single spoonful.

This is the arithmetic that the folk protocols work around, and it is why they are written as dilutions — a teaspoon of borax dissolved in a litre of water, of which a teaspoon or two is taken per day. Run honestly, those protocols land in the low milligrams of boron and therefore inside published limits. The hazard is not that the approach is inherently absurd; it is that the margin between "within the upper limit" and "twenty times over it" is one measurement error, using a kitchen spoon, with an unlabelled industrial-grade powder that carries no dosing information because it was never sold to be swallowed.

If the goal is boron, a standardised boron supplement delivers a known number of milligrams per capsule and removes the arithmetic entirely. That is the argument for the supplement over the laundry box, and it does not require believing anything bad about borax.

The Safety Record

Two different questions get conflated here, and separating them resolves most of the argument.

Acute toxicity is low

Swallowing a small amount of borax once is not a medical emergency for an adult. Its acute oral toxicity is genuinely low — in the same broad range as table salt, which is the basis of the frequently repeated "safer than salt" line. That claim, restricted to acute toxicity in adults, is defensible.

Infants and large doses are a different matter

The historical record here is unambiguous and is the reason borates left the medicine cabinet. Borate compounds were once standard in antiseptic dusting powders, nappy-rash preparations, burn dressings and body-cavity irrigations. They were withdrawn from those uses as the toxicity became clear. The majority of documented borate deaths have been in infants, several from borate powder applied to broken skin — the 1958 New England Journal of Medicine report of boric acid poisoning in an infant is one of the cases that ended the practice. Fatal adult ingestions are documented too, including a 1992 case following ingestion of a boric acid product. Borate is cleared by the kidneys, so impaired kidney function raises the risk substantially.

Reproductive toxicity is the live regulatory issue

This, not acute poisoning, is why borax carries the warnings it does today. In the European Union, borax and related borates carry a harmonised classification of Repr. 1B, H360FD — "may damage fertility; may damage the unborn child" under the CLP Regulation, and they appear on ECHA's Candidate List of Substances of Very High Concern. The basis is testicular atrophy in rats, with the sensitive effect appearing around 17.5 mg boron per kg of body weight per day.

The human evidence is genuinely more reassuring than the rat data, and the page would be dishonest without saying so. Studies of workers with the highest occupational boron exposures in the world — borate miners and processors in Turkey and in China — have looked directly for the reproductive effects the animal data predicts and have largely not found them. Duydu and colleagues studied occupationally and environmentally exposed people in Bandırma, Turkey, and Scialli and colleagues reviewed the male reproductive literature with emphasis on highly exposed Chinese workers. Neither found the effects at real-world exposures. The honest summary is that the classification is driven by animal data at doses well above ordinary human exposure, and that the workers with the greatest exposure on earth do not show the predicted harm.

What this supports is a specific, narrow conclusion: routine household use of borax is not a reproductive hazard. What it does not support is deliberately raising your own intake to the top of the range, or the assumption that pregnancy is a fine time to experiment. The EU classification is the reason borax has been restricted in consumer products across Europe, and it is a real regulatory fact, not a rumour.

The "Borax Conspiracy" Claim

A widely repeated story holds that borax was an effective and openly discussed arthritis remedy in America until a specific regulatory action ended the conversation, and that the knowledge was suppressed to protect a market. Versions of it name a 1988 Federal Trade Commission settlement that supposedly barred the borax industry from discussing internal or medicinal uses.

What we could not find

Searches of FTC case records and enforcement material turn up no such 1988 settlement, no case name, and no docket. The claim is also structurally suspicious in the retellings that make it: they promise to name the case and then never name it, describing it only as "a case involving the borax company and certain advertising claims." An enforcement action is a public document with parties and a number. A regulatory event that cannot be cited is not a regulatory event.

We are stating this as a failure to verify, not as proof of a negative. If a reader can produce the docket, that would settle it. Until then it should be treated as unsupported.

What actually happened, and it is not a secret

The real regulatory history is documented, and it is much duller than the story:

  1. Borate antiseptics and dusting powders were withdrawn through the mid twentieth century as infant poisonings and deaths accumulated. This was a safety response to published case reports, not a commercial manoeuvre.
  2. The FDA banned borax as a food additive. That is a straightforward, on-the-record decision.
  3. The EU classified borates as reproductive toxicants under CLP and added them to the SVHC Candidate List, which is why European consumer availability changed around 2010.

Each step is public, dated and citable. None of them requires a hidden settlement to explain, and the timeline runs across roughly a century of separate decisions in different jurisdictions rather than one moment in 1988.

Where the story comes from

The modern version traces largely to an article by Walter Last, a retired chemist and naturopath, published in Nexus magazine in mid-2012 under the title "The Borax Conspiracy: How the Arthritis Cure has been Stopped." It was widely reproduced, went offline after his death, and has since been re-hosted on alternative-health sites. It is a real article by a real person. That is a statement about its provenance, not its evidentiary weight: a magazine essay is not a clinical trial, and the article's central historical claim is the one we could not verify.

The part underneath that is real

Strip away the conspiracy and there is a legitimate research question left, and it deserves to be stated fairly rather than discarded with the packaging.

Rex Newnham, an Australian soil and plant scientist, developed arthritis in the 1960s, reasoned from boron's role in plant calcium metabolism that it might matter in humans, and spent two decades on the question. His 1994 paper in Environmental Health Perspectives reported an inverse geographic association: in regions where boron intake is around 1 mg per day or less, estimated arthritis incidence ran 20–70%, while in regions with intakes of 3–10 mg it ran 0–10%. A small double-blind pilot study with Travers and Rennie in 1990 reported symptom improvement in supplemented participants.

These are real, citable, peer-reviewed publications. They are also ecological correlations and a pilot study with very small numbers, which is the weakest useful tier of evidence — the design cannot separate boron from every other thing that varies between a boron-rich region and a boron-poor one, from diet to sunlight to genetics to who gets diagnosed. Thirty years on, no large randomised trial has settled it either way. The subject is genuinely under-researched rather than settled in either direction, and the honest position is that boron for joint health is plausible and unproven, not proven and suppressed.

Two further points are worth keeping straight. First, none of this research used borax — it used boron supplements at known milligram doses. Second, "there is no large trial" is not evidence of suppression; boron is unpatentable and cheap, which is a sufficient and boring explanation for why nobody has funded a definitive study. See Boron for Arthritis and Joints for the clinical evidence in full.

Handling Borax Safely

For the household and structural uses on this page:

Key Research Papers

Every citation below has been verified against Crossref. Journal names and authors are given as plain text; the linked portion is the year, volume, issue and pages.

  1. Newnham RE. Essentiality of boron for healthy bones and joints. Environmental Health Perspectives. 1994;102(Suppl 7):83–85.
  2. Nielsen FH. Biochemical and physiologic consequences of boron deprivation in humans. Environmental Health Perspectives. 1994;102(Suppl 7):59–63.
  3. Nielsen FH. Update on human health effects of boron. Journal of Trace Elements in Medicine and Biology. 2014;28(4):383–387.
  4. Hunt CD. Dietary boron: progress in establishing essential roles in human physiology. Journal of Trace Elements in Medicine and Biology. 2012;26(2–3):157–160.
  5. Travers RL, Rennie GC, Newnham RE. Boron and arthritis: the results of a double-blind pilot study. Journal of Nutritional Medicine. 1990;1(2):127–132.
  6. Naghii MR, Mofid M, Asgari AR, Hedayati M, Daneshpour MS. Comparative effects of daily and weekly boron supplementation on plasma steroid hormones and proinflammatory cytokines. Journal of Trace Elements in Medicine and Biology. 2011;25(1):54–58.
  7. Scialli AR, Bonde JP, Brüske-Hohlfeld I, Culver BD, Li Y, Sullivan FM. An overview of male reproductive studies of boron with an emphasis on studies of highly exposed Chinese workers. Reproductive Toxicology. 2010;29(1):10–24.
  8. Duydu Y, Başaran N, Üstündağ A, Aydın S, Ündeğer Ü, Ataman OY, et al. Reproductive toxicity parameters and biological monitoring in occupationally and environmentally boron-exposed persons in Bandırma, Turkey. Archives of Toxicology. 2011;85(6):589–600.
  9. Connelly JP, Crawford JD, Soloway AH. Boric acid poisoning in an infant. New England Journal of Medicine. 1958;259(23):1123–1125.
  10. Restuccio A, Mortensen ME, Kelley MT. Fatal ingestion of boric acid in an adult. The American Journal of Emergency Medicine. 1992;10(6):545–547.

Primary Documents and Technical Reports

  1. Lebow ST, Lebow PK, Woodward BM, Halverson SA, Abbott W, West MM. Efficacy of a borax–copper preservative in exposed applications. USDA Forest Service, Forest Products Laboratory, Research Paper FPL-RP-655, Madison, WI, 2009. Full text (PDF).
  2. National Institutes of Health, Office of Dietary Supplements. Boron — Fact Sheet for Health Professionals. ods.od.nih.gov.
  3. Institute of Medicine. Arsenic, Boron, Nickel, Silicon, and Vanadium. In: Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academies Press, 2001. NCBI Bookshelf.
  4. European Chemicals Agency. Candidate List support document: disodium tetraborate, anhydrous. ECHA.
  5. National Capital Poison Center. Borates, borax, and boric acid: are they safe? poison.org.

Live PubMed Searches

  1. Boron and human nutrition
  2. Boron and bone metabolism
  3. Boron and arthritis
  4. Borax toxicity
  5. Boric acid poisoning
  6. Boron occupational reproductive toxicity
  7. Sodium tetraborate
  8. Boron and steroid hormones
  9. Borate wood preservatives

Connections

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