"Given Dr. Richard Kunin's 1989 analysis, it appears that the Chinese snake oil made from Chinese water snakes is very high in EPA. This substance is known to be a pain reliever, and the Chinese snake oil products may contain up to 4% of it. 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.
From a purely pharmacochemical perspective, it is likely that the genuine Chinese snake oil is not fraudulent, at least for its intended purpose. On the other hand, American products made from rattlesnake fats, which have at most 1/3 of the EPA concentration of Enhydris chinensis fat, are likely to have been inferior or even useless for similar purposes. 19th century snake oil peddlers and apothecarians seldom had any serious knowledge of chemistry or pharmacology. It is likely that they did not understand the action mechanism of the Chinese product, or even know its functional ingredient. Instead of analyzing the authentic remedy, they tried to imitate it with unimpressive results. Such inferior or even fraudulent products gave snake oil the reputation it has today."