A Review of Topical Corrosive Black Salve

Abstract

Black salve is a compound derived from various inert ingredients, but it can be transformed into a corrosive ointment by the addition of bloodroot (Sanguinaria canadensis) or zinc chloride. Black salve products have been advertised as a natural remedy for many ailments, ranging from bee stings to skin cancer. This article reviews the current literature surrounding this compound, which in its corrosive form can be dangerous for use without medical supervision. Patients should be educated about the lack of objective evidence supporting the clinical efficacy of black salve as a skin cancer treatment, as well as the possible cosmetic defects resulting from tissue necrosis secondary to the effects of bloodroot and zinc chloride.

Introduction

Black salve topical products are used as an alternative therapy for everything from boils and bug bites to warts and skin cancer. Widespread use of the Internet has allowed for easy dissemination of non–peer-reviewed information on alternative therapies, often referring to anecdotal reports rather than objective, peer-reviewed studies. Additionally, it is questionable whether the original lesions referred to in testimonials were truly skin cancer because many lack documented biopsy results to confirm a cancer diagnosis. This reliance on anecdotal reports may lead patients to use a black salve product that is not scientifically proven to reliably cure skin cancer and can potentially lead to disastrous complications.

The components of black salve vary widely, from a combination of various innocuous ingredients to inclusion of bloodroot (Sanguinaria canadensis) or zinc chloride, which results in a corrosive topical agent capable of indiscriminately damaging healthy and diseased tissue alike and forming eschar (sloughed dead tissue). It is this escharotic form that has been marketed as an alternative skin cancer treatment, and although numerous testimonials exist, references about the clinical efficacy and associated risks are scarce. Common names of these corrosive black salve products include Can-X, CentreForce (formerly Cansema), Curaderm, HerbVeil8, Hoxsey's dark red paste, Mexican black salve, and PureCents.

Although black salve has a reputation as being an alternative treatment, its history includes significant roots in allopathic medicine. Frederic E. Mohs, the originator of Mohs micrographic surgery for skin cancer treatment, first performed the surgery using a fixed-tissue technique using a paste composed of stibnite (antimony sulfide), bloodroot extract (S. canadensis), and zinc chloride applied to the tissue to be excised.¹ In 1944, Mohs patented the paste and signed all rights over to the Wisconsin Alumni Research Foundation for $1. Dr. Mohs explained, “The purpose of patenting was to prevent others from doing so and selling [the paste] indiscriminately to persons not trained to use it with complete microscopic control.”¹ He went on to make arrangements to ensure that the fixative was supplied only to physicians certified to use it properly.

The use of this fixative in Mohs micrographic surgery fell out of favor in the 1970s, when multiple investigators, including Mohs himself, discovered the fresh-tissue technique was equivalent to the fixed-tissue technique for cancer clearance^1,2 yet was completed in 1 day, while the fixed-tissue technique took an average of 3–5 days.³

Around the same time of Dr. Mohs' discoveries, Harry Hoxsey, a self-proclaimed healer, marketed and sold a similar escharotic paste as a cancer remedy. Hoxsey eventually opened 17 clinics in the United States, promoting his “Hoxsey Cancer Treatment,” although he lacked objective evidence that any of his patients were indeed cured of skin cancer.^4,5 Eventually the sale of the Hoxsey Treatment was banned and his U.S. clinics shut down. One clinic in Tijuana, Mexico, established in 1963, remains operational today and still offers Hoxsey therapy.

This article reviews the literature for the benefits and risks of corrosive black salve use. This review is intended to educate providers and patients on current black salve literature and to warn providers about the potential dangers for patients engaging in unmonitored use of escharotic black salve.

Escharotic Agents

The two most common escharotic agents used in modern black salve preparations are bloodroot (S. canadensis) and zinc chloride. Bloodroot, a perennial plant native to eastern North America, was originally mixed with onions by the Native Americans to create an escharotic paste. Bloodroot contains the alkaloid sanguinarine, which causes oxidative DNA damage and apoptosis, thus leading to tissue necrosis.^6,7 Two independent studies suggest that sanguinarine contains anticancer properties; these studies found that (1) sanguinarine shows differential binding to various polymorphic nucleic acid conformations⁸ and (2) at micromolar concentrations it preferentially induces apoptosis in human squamous carcinoma cells over normal human epidermal keratinocytes.⁹ It is important to note that the differential response of cancer and normal cells to sanguinarine is only at very low doses. Typical bloodroot black salve preparations contain high doses of sanguinarine, which lead to the indiscriminate death of normal and cancerous cells alike and result in extensive tissue necrosis with possible secondary necrotizing vasculitis.¹⁰

Zinc chloride was popularized as an escharotic cancer treatment in the early 19th century by Canquoin of Paris, Bougard of Brussels, and Dr. J. Weldon Fell. It was then repopularized by Dr. Frederic Mohs in the 1940s. Dr. Mohs is credited with discovering that zinc chloride causes in vivo fixation, preserving the histologic tissue architecture. These discoveries were the basis for use of zinc chloride in modern-day escharotic pastes, although the exact mechanism of zinc chloride–induced necrosis remains unclear.

Production and Regulation

The U.S. Food and Drug Administration (FDA) does not oversee the manufacturing of herbal supplements but does monitor their marketing. Manufacturers and distributors are not obligated to disclose to the FDA or consumers what evidence they have to support their product's safety or claims before putting their products on the market. However, if products claim to cure, treat, mitigate, or prevent disease and are not proven safe and effective for their labeled use, they are considered unapproved new drugs marketed in violation of the Federal Food, Drug, and Cosmetic Act.¹¹ Beginning in 2008, the FDA has collaborated with the Federal Trade Commission to prevent the sale of fraudulent cancer cures by sending warning letters to companies illegally claiming that their product, including black salve, can be used to treat cancer on their websites.^12,13 Because of the rapidly changing content available on the Internet, it is difficult for the FDA to eradicate all false claims about black salve. At the time of this review, a simple Internet search yielded websites claiming black salve “completely eliminates abnormal tissue”¹⁴ and “can be applied safely to healthy skin tissue, even sensitive skin.…[It] does not affect healthy tissue, only neoplastic (cancerous) cells.”¹⁵

Despite regulation efforts, the public continues to have easy access to these ointments advertised as a cancer cure through do-it-yourself Internet recipes, Internet and local distributers, gifts from friends or relatives, and products brought back from trips abroad. To circumvent some of the barriers imposed by regulatory agencies, “animal” black salve products are being marketed and sold with manufacturer admissions that the ingredients for the banned human version and available animal version of their products are the same.¹⁶

These compounds are subject to poor quality control and may contain a wide range of active and inactive ingredient concentrations. Beyond manufacturer variation, Graf and colleagues (2007) reported that sanguinarine concentration varies between wildcrafted and cultivated bloodroot.¹⁷ Cultivated bloodroot has a slightly lower absolute concentration of sanguinarine (2.25–2.75 mg/100 mg dried rhizome) compared with wildcrafted bloodroot (2.81–3.96 mg/100 mg dried rhizome). Furthermore, the concentration of sanguinarine in wildcrafted bloodroot varies seasonally, being highest in early spring.¹⁷ Therefore, the concentration of the escharotic agent, sanguinarine, is variable depending on how the bloodroot was grown and what time of year it was harvested.

Clinical Outcomes

Although laboratory evidence documents anticarcinogenic effects of black salve ingredients (bloodroot and zinc chloride), no randomized clinical trials on the efficacy and safety of black salve products have been published. Lacking randomized clinical trials, the evidence for any benefits of black salve comes from published case reports, as shown in Table 1,^{18

–26} which details a spectrum of outcomes ranging from patient satisfaction,^18,19 unacceptable scarring,^20
–22 to invasive recurrent tumor^21,23 to ulcer complications²⁶ to death due to delayed definitive treatment.^21,24 Following are examples of published case reports describing the range of patient experiences with black salve.

Table 1.

Published Black Salve Case Reports

Author (Year)	Cancer	Biopsy proven?	Outcome	Residual cancer after black salve use?
Eastman et al. (2011)¹⁸	Unknown neoplasm on nose (patient suspected melanoma)	No	Complete loss of left nasal ala	Unknown
Osswald et al. (2005)¹⁹	BCC on nose	Yes	Defect healed by secondary intention	Unknown
Brown et al. (2001)²⁰	BCC on left cheek	Yes	Underwent 3 scar revisions	No
	SCC on right lower leg	Yes	Defect healed by secondary intention without complication	No
McDaniel and Goldman (2002)²¹	BCC on right temple	Yes	Defect healed by secondary intention; subsequent Mohs surgery to excise residual tumor	Yes
	BCC on right neck	Yes	Defect healed with triangular keloid scar; underwent scar revision surgery	No
	BCCs on nose, lip, and cheek	Yes	After black salve treatment, underwent Mohs surgery, partial maxillectomy; BCC metastasized to lymph nodes and bony sites; patient referred to oncology	Yes
Saltzberg et al. (2009)²²	BCC on left nasal ala	Yes	Complete loss of left nasal ala	Unknown
Jellinek and Maloney (2005)²³	BCC on nose and scalp	Yes	Defect healed with scar, over which the BCCs recurred; patient underwent Mohs surgery (10 stages for nose, 8 stages for scalp)	Yes
Laub (2008)²⁴	BCC on nose, lip, cheek	Yes	After black salve treatment, patient underwent Mohs surgery, partial maxillectomy; radical neck lymphadenopathy, radiation, and chemotherapy; patient developed multiple bony metastases and died	Yes
Cienki and Zaret (2010)²⁵	Malignant melanoma on chest	Yes	Referred to surgical oncology team	Yes
	Unknown subcutaneous abdominal nodules (patient suspected adenocarcinoma)	No	Development of enterocutaneous fistulae at two treatment sites; patient admitted, put on bowel rest, and discharged without complications	Unknown
Affleck and Varma (2007)²⁶	BCC on nose	Yes	Fair cosmetic outcome with depressed irregular scar on nasal tip	Unknown

BCC, basal cell carcinoma; SCC, squamous cell carcinoma.

A 51-year-old man who presented with a confirmed basal cell carcinoma on his nasal tip was offered Mohs micrographic surgery. Instead he preferred to self-treat the lesion with a bloodroot-based salve. After eschar formation and subsequent secondary intention healing, he was left with a depressed, irregular scar on the nasal tip and a fair cosmetic outcome. Twelve months after the bloodroot salve treatment tumor had not recurred, but he remains under long-term surveillance because there was no definitive proof (i.e., histology) that the tumor was completely eradicated.²⁶

A previously published case letter by the current authors details a patient who used a corrosive black salve product for a self-diagnosed skin cancer on the left side of his nose. The treatment resulted in necrosis and permanent loss of his left ala (Fig. 1). However, despite his cosmetic defect, the patient continued to support the use of black salve for skin cancer. Since his black salve use 11 years ago, there has been no tumor recurrence on or near the left side of his nose.¹⁸ A similar report by Saltzberg and colleagues also describes the complete loss of the nasal ala due to black salve use.²²

FIG. 1.

Probable melanoma treated with black salve. Picture of patient after use of a black salve product (left), and the subsequent loss of his left nasal ala due to tissue necrosis (right).¹⁸ Reprinted with permission from the Journal of the American Academy of Dermatology.

Metastasis of basal cell carcinoma is uncommon (<1%), but the frequency of metastasis increases according to the size of the primary cancer (up to 50% for tumors >10 cm in diameter).²⁷ An example of this is a case of a 52-year-old man who originally presented with a biopsy-proven basal cell carcinoma of the left side of his nose. In lieu of definitive surgery to remove the tumor, he elected to treat it with black salve, which achieved apparent clinical resolution. However, 11 years later, the cancer recurred in the same area and penetrated to a level that necessitated two stages of Mohs micrographic surgery, a partial maxillectomy, a radical neck lymphadenectomy, and radiation therapy. The cancer subsequently metastasized to distant bony sites, and despite systemic chemotherapy the patient died.²⁴ Whether the recurrence was due to a failure of black salve to remove all residual cancer cells or to a new occurrence of cancer is unknown. Basal cell carcinoma rarely spreads to the bone, but this metastasis has been reported by others.²⁸

Standard Therapy

Surgical excision, electrodessication and curettage, and Mohs micrographic surgery are the current standards of care for skin cancer treatment. It should be recognized that the standard of care, although an excellent management strategy, is imperfect for several reasons: 1) If a lesion is assumed to be contiguous, islands of residual tumor may possibly be left behind in the normal tissue; 2) time constraints in performing Mohs surgery do not allow for routine use of immunostains and cell markers, thus causing some tumor types to be difficult to identify microscopically and possibly overlooked;²⁹ and 3) the health care provider may make technical errors. No skin cancer treatment is curative 100% of the time, but the high success rate of these techniques, in addition to other factors outlined in Table 2, makes the standard of care a superior choice over corrosive black salve.^30

–33

Table 2.

Comparison of Black Salve with Mohs Micrographic Surgery

Factor	Black salve	Mohs micrographic surgery (standard of care)
Success (no skin cancer recurrence)	Statistics unknown	Nonmelanoma skin cancer:^30 –32 M: 67%–99% SE: 80%–100% EDC: 92%–98%	Melanoma³³ M: 67%–99.5% SE: 80%–100%
Efficiency	Complete in days to weeks	Complete in 1 day
Precise anatomic control	Difficult	Easy
Conservation of normal tissue	Fair to poor	Good to fair
Repair	Delayed, secondary intention	M and SE: Immediate, primary closureEDC: Delayed, secondary intention
Cosmetic appearance	Good to poor	Good to fair
Evidence-based trials	No	Yes

EDC, electrodessication and curettage; M, Mohs micrographic surgery; SE, surgical excision.

The scarring that results from initial black salve treatment can obscure the tumor and disrupt the lesion continuity that is essential for optimal surgical performance. Therefore, surgical treatment is best used as a first-line treatment and not as a second-line treatment after black salve therapy.

Risks

One risk that accompanies self-treating with corrosive black salve is the patient's belief that clinical resolution of the lesion equates to histopathologic clearance of the lesion, which it does not. Because of the escharotic character of black salve, this treatment may destroy both cancerous skin and healthy skin to a degree that eradicates the local cancer.²⁰ However, without proper evaluation, which includes a conclusive biopsy, there can be no guarantee that all the cancer cells have been completely eliminated. If residual cancer cells are present after treatment, the cancer will recur; the lesion may then require excision or the cancer may metastasize to other sites in the body.^21,24 In addition, if suspicious lesions are not biopsied to rule out cancer, the corrosive salve may cause unnecessary skin damage in the case of a benign mole or lesion. Self-treatment with corrosive black salve may also result in a substantial delay in definitive diagnosis and surgical treatment of melanoma, which increases the risk of metastasis or deeper penetration of the lesion.^21,24,25

Many black salve users do not understand the potential consequences of this product. Health care providers should communicate clearly that although black salve is labeled as “natural,” the salve is not necessarily safe or harmless. Providers should maintain an open dialogue with patients who are interested in using these products and thoroughly educate them on the risks, the range of aesthetic outcomes, and allopathic treatment options. Escharotics may potentially lead to elimination of all tumor cells, but patients may not be satisfied with the cosmetic outcome and choose to undergo scar revision surgery, as other dissatisfied patients have.^20,21

Conclusions

Given the wide range of available skin cancer treatment options, some patients prefer naturopathic/homeopathic treatment regimens, such as black salve, over the current standard of care of surgery or electrodesiccation and curettage. However, the modern public may not fully understand the lack of objective data on the efficacy of black salve products in predictably curing skin cancer. They may also be unfamiliar with the potential risks associated with this corrosive compound, such as significant cosmetic defect, unconfirmed clearance of all cancer cells, and cancer recurrence or spread.

Because of the widespread availability of black salve products, providers should be familiar with this compound and its potential dangers. It is important to keep an open dialogue with patients about alternative medicine, while striving to effectively impart evidence-based information for the patient's decision-making process. Although patients should be appropriately counseled about their treatment options, providers must ultimately respect a patient's autonomy to choose the course of treatment.

As evidenced here, a variety of outcomes are possible after the use of corrosive black salve, ranging from patient satisfaction and cancer eradication to significant morbidity, suboptimal treatment, and death.^{18

–25}

The difficulty lies with the unpredictability of patient use, varied product quality, inconsistent user directions, and lack of regulation surrounding this compound. Such unpredictability puts patients at increased risk of adverse outcomes and is unnecessary in a time when the standard of care is scientifically proven to be safe, predictable, and effective in cancer eradication. It is important to note that Dr. Mohs patented his salve to prevent the widespread use of a potentially dangerous topical treatment by untrained persons; however, today this is exactly what is happening with the unregulated distribution of escharotic agents for unmonitored home use by the general public.¹

The concept of black salve as a cancer treatment is not unfounded, as some escharotics agents have been shown to have anticarcinogenic properties, but randomized controlled trials comparing them to standard therapies are lacking.^23,34 A small, preliminary clinical trial comparing trichloroacetic acid (another type of escharotic agent) with other types of treatments has shown promise for reducing the development of nonmelanoma skin cancer.³⁵ Because of the documented corrosive nature of black salve, enough tissue necrosis can occur to eradicate cancerous cells; however, the resultant collateral damage to surrounding normal tissue can be unacceptable and unsafe and does not constitute optimal medical care.^{1,10,20

–25} Sanguinarine possesses the potential for development as a topical skin cancer treatment as a result of the differential response of squamous carcinoma cells and epidermal keratinocytes documented by Ahmad and colleagues.⁹ However, more investigation is needed to determine its safety, the optimal concentration necessary to target cancer cells while minimizing damage to normal cells, and its efficacy as a topical chemotherapy. In the future, we recommend randomized, double-blinded clinical trials testing the efficacy, safety, and therapeutic dose of sanguinarine for topical treatment of skin cancer.

Footnotes

Acknowledgments

Supported by the US Department of Veterans Affairs and the Department of Health Services Research & Development of the Veterans Affairs Puget Sound Health Care System. The views expressed in this article are those of the authors and do not necessarily reflect the position or policy of the Department of Veterans Affairs or the United States government.

Author Disclosure Statement

No competing financial interests exist.

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