Here the short version – black salve is a fake cancer cure that is dangerous pseudoscience. It is one of those treatments that is so bad it pushes the limits of credulity, and in this case it is directly harmful in the extreme.

As I have discussed before, black salve is sold as a “natural” herbal-based cancer treatment. It is an escharotic topical treatment, which means that it is corrosive to skin and other tissue, resulting in the formation of a thick scab, or “eschar”. The main ingredient is Sanguinaria canadensis, which contains a number of phytochemicals and the alkaloid poison, sanguinarine.

Sanguinarine [13-methyl (1,3) benzodioxolo(5,6-c)-1,3-dioxolo (4,5) phenanthridinium] is a toxin that kills animal cells through its action on the Na+-K+-ATPase transmembrane protein.

You will notice that it kills “animal cells”. The fact that it can be derived from a plant is irrelevant. It is a powerful caustic substance that eats through all tissue. But of course, there are always layers of complexity that can be cherry picked through motivated reasoning to pain an alternate reality. There are studies that show that sanguinairine, in specific concentrations, may have more toxicity to some type of cancer cells than to healthy cells. This is often the case, because cancer cells are highly metabolic. At the same time, some forms of cancer are relative resistant to its effect. None of this means you can safely slather it on your skin and it will leave healthy tissue untouched while eating away all cancer cells. As one review notes:

However, in vitro studies of sanguinarine suggest it causes indiscriminate destruction of healthy and cancerous tissue at doses higher than 5 µM, limiting its practical utility.

“Indiscriminate destruction” is not a feature rational people value in medicine.

Still those selling and promoting black salve claim the opposite of what the evidence shows. It is a dangerous distortion of reality. Black salves containing sanguinairine eat through any tissue, leaving behind horrific wounds and scars. There are many case reports of morbidity and even mortality from using black salve. Also, ironically, sanguinairine is potentially carcinogenic – which means it may produce cancerous cells.

Reviews of cases and research seem to employ ironic understatement when summarizing the clinical effects of using caustic paste to self-treat lesions and cancer. For example:

…case study reports of excessive scarring, deformity, and treatment failure.


…suboptimal therapeutic and cosmetic outcomes associated with its use.

Yes, I consider causing a massive wound that later becomes infected, a disfiguring scar, and failing to actually remove the cancer, to be “suboptimal”.

It is also important to understand the psychology at work, especially from the perspective of someone trying to promote science-based medicine. People who consider using black salve for known cancer or a suspicious lesion are faced with two broad choices. On the one hand, you can have an expert evaluate your disease, and if necessary precisely excise the lesion, examining the borders microscopically to make sure they are clean, and therefore any potential cancer is removed. The treatment is evidence-based and designed to produce the optimal chance of a cure with the minimum scarring necessary.

Or – you can treat yourself with a black paste you purchased online, applying it to your skin until you leave a nasty hole in your body. You may have no idea if the lesion was cancer to begin with, you have no idea if you removed it all, and the scarring is far more than was necessary to remove the lesion. But, this treatment is “natural.” You were also empowered to treat yourself, so you can take comfort from that every time you look in the mirror.

Black salve persists despite the obvious facts because a compelling narrative can be more powerful than reality. When people are plied on a regular basis with conspiracy theories and false narratives, even otherwise intelligent and well-meaning people can get to a place where incredibly bad decisions seem reasonable.

Psychologically, people want the magic salve. Medicine always involves some trade-offs, and practitioners should be transparent about what those trade-offs are. They may be minor, like you have to take medicine or change your lifestyle, or it may be significant, like undergoing a major procedure or getting the equivalent of chemotherapy. Alternative medicine often promises magical treatments without trade-offs – no risk, no side-effects, etc. The lure of such false promises is just too great for some people, especially if it is packaged inside a comforting narrative.

The marketing of unrealistic promises with compelling narratives has been given a huge boost by social media, which is increasingly a battleground between the forces of quackery and consumer protection. A recent investigative report shows how the promotion of black salve is still thriving online, despite promises from major outlets to crack down. Youtube, for example, says it is against its policy to promote health misinformation on its platform, and it will remove videos if reported. However, it is still easy to find videos promoting black salve on Youtube, so whatever process it is using is not adequate.

Facebook is much worse, and will not categorically ban pages promoting black salve (like “SW Florida Black Salve”, which is directly selling it). They will, instead, change their algorithm to not promote such pages. But of course they are easy to find if you search.

It is illegal to sell black salve in the US, but you can still buy it online from international sellers. I would think that promoting or selling an illegal health product is a pretty bright line for banning content. I understand the complexity of banning something as vague and sometimes subjective as “misinformation”, but illegal products banned by the FDA are not ambiguous or subjective.

I did submit a report to the FDA concerning SW Florida Black Salve, so we will see what kind of response we get. Reporting often does work, as does complaining to Youtube and to a lesser extent Facebook. Vigilance on the part of consumer protection outlets will always be necessary, but it is a game of whack-a-mole. Systemic protections are necessary. Black salve is clearly dangerous quackery, so it is low hanging fruit, and therefore a good indicator of how the system it working. At present – not good enough.


Posted by Steven Novella

Founder and currently Executive Editor of Science-Based Medicine Steven Novella, MD is an academic clinical neurologist at the Yale University School of Medicine. He is also the host and producer of the popular weekly science podcast, The Skeptics’ Guide to the Universe, and the author of the NeuroLogicaBlog, a daily blog that covers news and issues in neuroscience, but also general science, scientific skepticism, philosophy of science, critical thinking, and the intersection of science with the media and society. Dr. Novella also has produced two courses with The Great Courses, and published a book on critical thinking - also called The Skeptics Guide to the Universe.