Snake oil is a traditional Chinese medicine made from the Chinese water snake (Enhydris chinensis), which is used to treat joint pain. However, the most common usage of the phrase is as a derogatory term for compounds offered as medicines that implies that they are fake, fraudulent, quackish, or ineffective. The expression is also applied metaphorically to any product with exaggerated marketing but questionable or unverifiable quality or benefit.
Snake oil originally came from China, where it is called shéyóu (蛇油). There, it was used as a remedy for inflammation and pain in rheumatoid arthritis, bursitis, and other similar conditions. Snake oil is still used as a pain reliever in China. Fats and oils from snakes are higher in eicosapentaenoic acid (EPA) than other sources, so snake oil was actually a plausible remedy for joint pain, as these are thought to have inflammation-reducing properties. Snake oil is still sold in traditional Chinese pharmacy stores.
Snake fat also played a role in ancient Egyptian medicine, mixed with the fats of lion, hippopotamus, crocodile, tomcat, and Nubian ibex into a homogeneous mass believed to cause bald men to grow hair.
Chinese labourers on railroad gangs involved in building the Transcontinental Railroad to link North America coast to coast gave snake oil to Europeans with joint pain. When rubbed on the skin at the painful site, snake oil was claimed to bring relief. This claim was ridiculed by rival medicine salesmen, especially those selling patent medicines. In time, snake oil became a generic name for many compounds marketed as panaceas or miraculous remedies whose ingredients were usually secret, unidentified, or mis-characterized and mostly inert or ineffective, although the placebo effect might provide some relief for whatever the problem might have been.
Patented snake oil remedies originated in England, where a patent was granted to Richard Stoughton's Elixir in 1712. Since there was no federal regulation in the USA concerning safety and effectiveness of drugs until the 1906 Food and Drugs Act and various medicine salesmen or manufacturers seldom had enough skills in analytical chemistry to analyze the contents of snake oil, it became the archetype of hoax. American snake fats have EPA contents markedly lower than those of the Chinese water snake. Thus, the American snake oils were even less effective in relieving joint pain than the original Chinese snake oil, further promoting the hoax stereotype.
The snake oil peddler became a stock character in Western movies: a travelling "doctor" with dubious credentials, selling some medicine (such as snake oil) with boisterous marketing hype, often supported by pseudo-scientific evidence, typically bogus. To enhance sales, an accomplice in the crowd (a shill) would often "attest" the value of the product in an effort to provoke buying enthusiasm. The "doctor" would prudently leave town before his customers realized that they had been cheated. This practice is also called "grifting" and its practitioners are called "grifters".
The practice of selling dubious remedies for real (or imagined) ailments still occurs today, albeit with some updated marketing techniques. Claims of cures for chronic diseases (for example, diabetes mellitus) for which there are reputedly only symptomatic treatments available from evidence-based medicine are especially common. The term snake oil peddling is used as a derogatory term to describe such practices.
An alternate theory for the origins of the term snake oil is that it was a corruption of Seneca oil. The Senecas, a tribe in the Eastern United States, were known to use petroleum from natural seeps as a liniment for skin ailments. However, Native Americans are known to have used rattlesnake fat and the herb snakeroot for various purposes.
The composition of snake oil medicines varies markedly between products.
The Chinese water snake (Enhydris chinensis) is the richest known source of EPA, the starting material the body uses to make the series 3 prostaglandins. These prostaglandins are the biochemical messengers that control some aspects of inflammation, rather like aspirin, which also affects the prostaglandin system. Like essential fatty acids, EPA can be absorbed through the skin. Salmon oil, the next best source, contains 18% EPA. Rattlesnake oil contains 8.5% EPA.
(Note that this makes the above similar in composition to modern-day capsaicin-based liniments. Thus, this early snake oil may have worked somewhat as intended, even if it did not contain its alleged ingredients.)
Richard Kunin, a proponent of orthomolecular medicine, wrote a 1989 letter to the editor arguing that oil made from Chinese water snakes is very high in EPA. This substance is known to be a pain reliever, and Kunin argued that it might provide an explanation for the traditional use of snake oil. Snake oil does not have the dubious reputation in China that it has in the US and elsewhere in the Western world, and it is used widely in traditional Chinese medicine. However, it is not seen as a panacea in China either; there, it is used only as relief for arthritis and joint pain.
English musician and comedy writer Vivian Stanshall satirized a miracle cosmetic as "Rillago—the great ape repellent".
The band Alkaline Trio has recorded a song entitled "Snake Oil Tanker".