What black salve and traditional drawing salves actually do to your skin

Black salve is an escharotic that destroys tissue without telling healthy from diseased. The published harm is disfigurement and delayed cancer diagnosis.

Two very different things get called drawing salves. One is a family of traditional pastes, some of them licensed medicines, that claim to soften skin and encourage a boil to discharge. The other is black salve, a corrosive escharotic sold online as a cancer treatment, which destroys whatever tissue it touches and has a published record of disfigurement and delayed diagnosis. This page separates them and sets out what the evidence shows about each. It does not describe how to make or use either one.

• Escharotic: kills tissue by chemical burn
• Sanguinarine: Schedule 10 in Australia
• No marketing authorisation anywhere
• Cancer persisted in 34.2 percent of treated sites

What black salve is made of and what that chemistry does

Black salve is a family of preparations rather than a single product. The two constituents that recur are extract of bloodroot, Sanguinaria canadensis, which supplies the benzylisoquinoline alkaloid sanguinarine, and zinc chloride. Some versions carry one and not the other. Products marketed as red salve, cansema and various initialised trade names belong to the same category. Analytical work on commercial samples has found dramatic variation in the concentration of the constituents between manufacturers, so two jars bearing the same name are not the same product.

Both constituents are escharotics, meaning they kill tissue by chemical action and leave behind a thick black scab called an eschar. Zinc chloride is a strong Lewis acid and a powerful protein coagulant: it denatures the proteins of any cell it reaches and fixes the tissue in place, which is why a related zinc chloride paste was historically used to fix tissue for sectioning in early chemosurgery, under a surgeon's control, with microscopic examination at every stage. Zinc chloride is not zinc oxide, the insoluble, essentially inert powder used as a skin protectant and described in the zinc oxide profile. The two share a metal and nothing else. Sanguinarine is broadly cytotoxic in cell culture. Neither mechanism has any way of recognising a cancer cell, because protein coagulation and general cytotoxicity are properties of the chemistry, not of a targeting system. That one ingredient is a plant extract carries no weight, for the reason set out in chemical free and clean beauty claims: sanguinarine is a potent alkaloid, and botanical origin predicts nothing about how gently a molecule behaves.

Why the selectivity claim fails

The central marketing claim for black salve is that it seeks out and destroys diseased tissue while leaving healthy tissue alone. Three independent lines of evidence contradict it.

First, in vitro cytotoxicity. Sanguinarine alkaloids and zinc chloride are indiscriminately toxic to cells in culture. Selectivity would require a differential large enough to spare normal tissue at the concentration that kills tumour, and no such window has been demonstrated for a topical paste applied at unmeasured dose to unmeasured depth.

Second, histology from real patients. Croaker, Liu and Myers reviewed five years of Australian histopathology specimens from black salve treated sites and found necrosis of normal tissue in cases where the lesion treated turned out to be benign. Of the 475 lesions examined, 86 were benign, and those sites had been destroyed anyway. A selective agent applied to a harmless mole would do nothing.

Third, the case reports. The published harms are concentrated on the face, where the skin is thin and the underlying structures are close: nose, eyelid, ear. Case reports describe destruction extending into nasal cartilage requiring reconstructive surgery, full thickness loss of tissue on the breast, and wounds deep enough to need grafting. A 2025 case report describes a melanoma in situ self-treated with a black salve product that led to hospital admission and extensive tissue damage. Chemistry that respected tissue type would not produce that pattern of injury.

Why the eschar looks like proof, and why it is not

The experience that convinces people is consistent and easy to describe. The paste is applied, the area becomes inflamed and painful over a few days, a hard black plug forms, and after a week or two that plug separates and falls out, often leaving a crater that heals over. The plug is frequently described as the tumour coming out by the root, and photographs of it circulate as evidence.

The plug is an eschar. It is coagulated dead tissue: skin, blood, protein and whatever else the chemical reached, held together by the fixative action of the zinc chloride. It forms in exactly the same way over a benign mole, a skin tag, or normal skin, because its formation depends only on the chemistry meeting living tissue. It is not a structure the body builds around a tumour and it does not indicate that anything diseased was present, let alone removed.

The second problem is that nothing is ever examined. When a suspicious lesion is excised surgically the specimen goes to a laboratory, a pathologist confirms what it was and reports whether the margins are clear, and if they are not the patient is brought back. None of that happens with a salve. There is no specimen, because the tissue has been destroyed and discarded. The depth reached is unknown and uncontrolled, so a tumour extending deeper than the burn is left in place. And the wound heals over the top, so the surface looks resolved while disease continues underneath. That is precisely the pattern the Australian histopathology series documented in a third of cases: normal looking scar, cancer still there.

Where the regulators stand

No black salve product holds a licence, authorisation or registration as a medicine in any major jurisdiction. The positions are explicit rather than merely absent.

Australia. The Therapeutic Goods Administration has published a safety alert on black and red salves in treating cancer. It states that the products are corrosive and can cause serious harm, destroying layers of skin and surrounding healthy tissue with pain, scarring, ulceration, swelling and infection, and that the TGA is not aware of any credible scientific evidence that any black or red salve preparation is effective in treating cancer. The products are not entered in the Australian Register of Therapeutic Goods. Sanguinarine appears in Schedule 10 of the Poisons Standard, the schedule reserved for substances considered so dangerous to health that they are prohibited from sale, supply and use. The TGA has executed search warrants, seized bloodroot salve and capsules, and prosecuted individuals for unlawful supply and advertising.

United States. The Food and Drug Administration lists black salve among fake cancer cures consumers should avoid and has issued warning letters to companies selling products claiming to prevent, diagnose, treat or cure cancer without approval, including bloodroot preparations. The agency's guidance is that people should not use black salve, or salve products containing sanguinarine, Sanguinaria canadensis or bloodroot, alone or with zinc chloride, as an alternative to proven therapies, and that doing so can result in permanent disfigurement.

United Kingdom. There is no black salve product with a marketing authorisation from the Medicines and Healthcare products Regulatory Agency. Under the Human Medicines Regulations 2012 a product presented as treating or preventing disease is a medicinal product, and placing an unauthorised medicinal product on the market is an offence. The MHRA's standing position on unlicensed medicines bought online is that they may contain impurities or incorrect ingredients and that there is no way to know whether they were made to acceptable standards. The British Association of Dermatologists warns against black salve directly, describing the wounds and scarring it causes as often requiring plastic surgery to repair. The reason a product like this can be sold at all is that it is marketed outside the medicines system while making medicinal claims, which is the same regulatory line explained for makers in cosmetic versus drug claims.

There is also a genotoxicity question layered on top. Croaker and colleagues reviewed the carcinogenic potential of sanguinarine and reported that mice given sanguinarine chloride showed bone marrow changes suggestive of genotoxicity. That evidence is animal and preliminary, and it is not the reason to avoid the product, but applying a possibly genotoxic compound to skin in the hope of treating a cancer is an unattractive gamble on any reading.

The other category: traditional drawing pastes

Traditional drawing salves are a genuinely separate thing and should not be tarred with the same brush, though the evidence for them is thinner than their reputation suggests. Two are worth naming because they are real, regulated products rather than internet preparations. A third group, the plant salves such as calendula salve, contains no drawing agent at all and works by occlusion and emollience, which is what any anhydrous balm does.

Ichthammol, also sold as ammonium bituminosulfonate, is a dark, strongly smelling material made by sulphonating shale oil. It has been used in dermatology since the nineteenth century and is the classic drawing ointment for boils and abscesses, typically at around 10 to 20 percent in a petrolatum or wool fat base. Laboratory work supports anti-inflammatory activity, including effects on prostaglandin synthesis, and some antibacterial activity against Staphylococcus aureus. What is missing is clinical trial evidence: reviewers looking specifically for double blind placebo controlled trials of ichthammol for abscesses and furuncles have not found them, and there are no systematic studies of shale oil sulphonates used as abscess drawing agents. The proposed mechanism, softening the overlying skin so that pus discharges more readily, is plausible and untested.

Magnesium sulfate paste BP is a licensed medicine in the United Kingdom with a pharmacopoeial monograph, containing dried magnesium sulfate at around 45 to 48 percent with glycerol and about 0.5 percent phenol. Its indication is as a drawing paste for minor skin infections including boils. The mechanism is osmotic: a very concentrated salt paste held against the skin under a dressing draws fluid outward along the water potential gradient. That is straightforward physics, and it is the strongest mechanistic case any drawing preparation has. Its clinical evidence base is nonetheless largely traditional rather than trial derived, and it is not a treatment for an established abscess.

Does anything actually draw through intact skin?

The folk claim is broad: that a salve pulls out splinters, glass, thorns, venom, infection, toxins and metal. There is no controlled evidence that any topical preparation moves a solid foreign body through intact skin, and there is no proposed mechanism that survives inspection. A splinter is held by the tissue closed around it. Nothing applied to the surface generates a force on it. What a greasy occlusive dressing does do is hydrate and soften the stratum corneum considerably over several hours, which can make a superficial splinter easier to grip, and can macerate the skin enough that a shallow one works its way out on its own. That is a real but modest effect and it is a property of occlusion, not of any special ingredient. The same softening happens under plain petrolatum, and the physics of it is in occlusive, emollient and humectant. Pine resin carries the drawing reputation most strongly in the English speaking tradition, and the pine resin salve page treats it as the tacky, protective, mildly antimicrobial dressing it is rather than as an extraction agent. Kaolin and cosmetic clays attract the same claim with the same flaw: they absorb what is already on the surface and reach nothing below it.

Venom is worse than unsupported. Snake and spider venom is delivered into tissue and enters the lymphatic and vascular systems within minutes. Nothing on the skin surface reaches it, and time spent applying a paste is time not spent getting to hospital. Toxin drawing claims of the detox variety have no defined referent: no named substance, no measurement, no way to test the claim. Infection is the same story in a different register. An established abscess is a walled off collection of pus with a fibrous capsule that antibiotics penetrate poorly and topical preparations do not penetrate at all.

What actually deals with a splinter, a boil or an abscess

For a splinter, the practical answer is soap, water, clean fine tweezers, magnification and good light, pulling along the angle of entry. Deep, large, dirty or glass fragments, anything in a joint, a hand, a foot or near an eye, and anything you cannot remove in a couple of careful attempts, belong to a clinician. Tetanus status matters for a dirty puncture.

For a small boil or folliculitis, warm compresses several times a day, cleanliness and time are the standard conservative measures. A boil that points and discharges on its own usually settles. Squeezing it is the classic way to push infection deeper.

For an abscess, the definitive treatment is incision and drainage, and this is a clinician job for reasons that are not about gatekeeping. It requires anaesthesia, a sterile field, adequate exposure to break down internal loculations, a decision about packing, and judgement about whether antibiotics are needed alongside. Cutting into an abscess at home risks bacteraemia, deeper spread, damage to structures you cannot see, and a worse scar. Get medical help urgently for a rapidly spreading red area, red streaking, fever or feeling unwell, an abscess on the face, hand or near the spine, or any infection in someone with diabetes or a suppressed immune system.

The decision rule

Any lesion that bleeds, crusts, changes shape or colour, itches persistently, or fails to heal within four weeks needs to be assessed by a clinician, not covered with a salve of any kind. That four week rule of thumb is the one used in public skin cancer awareness guidance, and its whole purpose is to catch the lesions that people are inclined to wait out. Waiting is the harm that black salve causes most often: not the burn, which is visible and eventually heals, but the months of apparent resolution during which a treatable cancer grows.

Three limits on what this page can do. It cannot tell you what a lesion on your skin is, and no photograph, ingredient list or description can substitute for someone looking at it. It cannot rule out that ichthammol or magnesium sulfate paste help with boils, because absence of controlled trials is not evidence of absence, and both are legitimately available products used under pharmacist and clinician advice. And it cannot make the eschar story less convincing to someone who has watched one form, which is why the argument here rests on histopathology from hundreds of treated sites rather than on anyone's photographs. How Trebalm handles claims of this kind is set out in editorial standards, and the vocabulary distinguishing a salve from an ointment or a balm is in balm versus salve versus ointment versus cream.

Reviewed and updated 6 September 2026. Spotted an error? Tell us and we will fix and log it.