Many salves, pastes, poultices, and plasters have been applied directly to tumors with the hope of burning them away. Zinc oxide, bloodroot, and several other herbs are common ingredients. Some marketers claim that corrosive agents (sometimes called "black salves") can "draw out" the cancer. In recent years, scientists have found chemicals that can destroy certain superficial skin cancers. Except for these, however, corrosive agents are worthless against cancer and cannot be legally marketed for that purpose in the United States.

Corrosive salves are often referred to as "escharotics" because they produce a thick, dry scab called an "eschar" on the skin. Their use to treat cancer dates back hundreds of years, perhaps even to ancient times. Their use was fairly common during the 18th and 19th centuries. If a tumor is confined to the superficial layers of the skin, it would be possible to burn it off with a corrosive salve or paste. Unfortunately, products capable of accomplishing this can also burn the surrounding normal tissue and result in unnecessary scarring. For superficial cancers—for which the cure rate with standard treatment is nearly 100%—it makes much more sense to use standard methods that can destroy the cancer with little or no damage to the nearby tissues. Some salves are also promoted for treating herpes, venereal, diseases, diabetes, and lupus.

This idea that eschartics can "draw out" cancers from underneath the skin is preposterous. Furthermore, even if a product could do this, it could not influence cancers that have spread (metastasized) to distant regions of the body.

Some currently marketed escharotics contain bloodroot (Sanguinaria candensis), zinc chloride, or both. However, because cancer salves are not manufactured under government supervision, it may not even be possible to know what is in them. People who use such products without benefit of medical consultation run additional risks. Untrained individuals may incorrectly conclude that a growth is cancerous when it is not. Skin cancers that can spread should be medically investigated to see whether they have done so, and some of these require extensive treatment even though they might not look dangerous to the naked eye. In addition, although escharotics may appear to destroy cancers on the surface of the skin, the user will not be able to tell whether cancer remains under the skin where it can continue to grow without immediate detection.



[link to www.quackwatch.org]