Via a Bad Science topic: George Fulford and Victorian Patent Medicine Men: Quack Mercenaries or Smilesian Entrepreneurs? (PDF), an interesting article at the Canadian Bulletin of Medical History. Looking to the late 19th century, there are strong parallels with the present-day animosity between between mainstream medicine and quackery.
The article focuses on what it argues was the more benign side of the business: patent medicines such as antacids and laxatives that maybe even did a little good. Nevertheless they came with extravagant claims that went well beyond their actual effect. Clarke's Blood Mixture, an iron supplement, claimed to treat "scrofula, scurvy, sores of all kinds, skin and blood diseases". Then as now, it was big business: the maker of Clarke's Blood Mixture, advertised in The Times, could afford to spend £20,000 a year on advertising. Also as now, they leaned heavily on testimonials rather than proven evidence. Encouragingly, the consumer sometimes won: in the classic Carbolic Smoke Ball Case and Medical Battery Case, vendors were successfully taken to court when their remedies failed to deliver.
On the downside, sometimes court appearances made no difference. In 1905, in the Bile Beans Case, the maker of the laxative Bile Beans unwisely tried to sue an imitator, and was forced to disclose in court that the product's backstory ... Charles Forde, an eminent scientist, thoroughly investigated the healing extracts and essences of Australian roots and herbs and after long research he found himself the discoverer of a natural vegetable substance which was beyond all doubt the finest remedy yet discovered ... was totally fictitious. This didn't stop the product continuing to sell, successfully, well into the 1980s. Interactions between the British and American Patent Medicine Industries 1708-1914 (PDF) gives further insight into the large market for such products in the past.