Health fraud

Quackery is the promotion of fraudulent or ignorant medical practices. A quack is a "fraudulent or ignorant pretender to medical skill" or "a person who pretends, professionally or publicly, to have skill, knowledge, or qualifications he or she does not possess; a charlatan or snake oil salesman". The term quack is a clipped form of the archaic term , from Dutch: kwakzalver a "hawker of salve". In the Middle Ages the term quack meant "shouting". The quacksalvers sold their wares on the market shouting in a loud voice.

Common elements of general quackery include questionable diagnoses using questionable diagnostic tests, as well as untested or refuted treatments, especially for serious diseases such as cancer. Quackery is often described as "health fraud" with the salient characteristic of aggressive promotion.

Since it is difficult to distinguish between those who knowingly promote unproven medical therapies and those who are mistaken as to their effectiveness, U.S. courts have ruled in defamation cases that accusing someone of quackery or calling a practitioner a quack is not equivalent to accusing that person of committing medical fraud. To be both quackery and fraud, the quack must know they are misrepresenting the benefits and risks of the medical services offered (instead of, for example, promoting an ineffective product they honestly believe is effective).

In addition to the ethical problems of promising benefits that can not reasonably be expected to occur, quackery also includes the risk that patients may choose to forego treatments that are more likely to help them, in favor of ineffective treatments given by the "quack".

Stephen Barrett of Quackwatch defines quackery "as the promotion of unsubstantiated methods that lack a scientifically plausible rationale" and more broadly as:

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