This article originally appeared on Time.com.
The quest for a health is a natural human response to illness, but medical history provides plenty of reason to think twice before you try that miracle cure.
Case in point: medieval doctors would press a sacrificed puppy, kitten, rabbit or lamb on top of a tumor because they thought that cancer was like a “ravenous wolf” that would rather “feed off the sacrificed animal rather than the human patient,” as Dr. Lydia Kang and her co-writer Nate Pedersen put it in their new book Quackery: A Brief History of the Worst Ways to Cure Everything.
Sure, some of the stranger examples of old-time medicine would turn out to be useful; while cautery—heating an iron stick on hot coals and then pressing it onto a person’s body—didn’t end up curing broken hearts when the rod was pressed against the patient’s chest, the practice was a forerunner to electric surgical instruments. And while doctors were misguided in prescribing the poison arsenic to treat syphilis and skin conditions, a form of the chemical has been used to treat acute promyelocytic leukemia.
But plenty of other techniques were downright useless, if not dangerous. Early women’s health recommendations included everything from naturalist Pliny the Elder’s insistence that consuming powdered sow’s dung relieved labor pains, to the medieval Italian advice that keeping weasel testicles near one’s bosom was an effective form of contraception. And in American history, misguided medicine ran rampant, especially before steps such as the 1906 Food and Drugs Act, the first major consumer protection law to crack down on misleading food and drug labels, and the formation of the Food and Drug Administration in the ’30s. Even today, despite increased consumer protection, misleading medical claims are still out there.
“We have to be really careful when we’re looking for an easy cure,” Kang tells TIME. “Generally things aren’t that easy, so that should make you a little bit suspicious.”
TIME spoke to Kang about some of the practices once touted as good medicine that are well known to be harmful today.
During a 1665 plague outbreak in London, schoolchildren were told to smoke cigarettes, which at the time were thought to be disinfectants. In addition, “tobacco smoke enemas”—the source of a common idiom about blowing smoke—were developed as a sort of 18th-century version of CPR by members of The Institution for Affording Immediate Relief to Persons Apparently Dead from Drowning. They would drag the victim out of the River Thames, strip him or her down, and use an enema to literally blow smoke into the person, either manually or with bellows. (Mouth-to-mouth resuscitation was invented in the ’50s.)
In 1964, a U.S. Surgeon General report would label cigarettes deadly and urge people to stop smoking.
The phrase “you are what you eat” can apply to this school of thought. Ancient Romans clamored for gladiator blood for strength and vitality, but it was also thought to be a cure for epilepsy. That rationale appeared to be maintained for centuries, based on Englishman Edward Browne’s 1668 observation that people attended executions to collect the blood of the victims. In the early 1600s, one German physician’s suggested cure for a range of conditions was making a jerky of sorts out of the corpses of 24-year-old redheads, chopping up their bodies and mashing the bits in wine, myrrh and aloe, before dry-curing them.
Now that it’s known that blood can carry disease, the risks of drinking it are obvious — but the use of other people’s body parts for medicine would be legitimized through the development of organ donation and transplantation in the mid-20th century.
In the early 1900s, when people walked into the spa by in Joachimsthal, Czech Republic, they immediately breathed in irradiated air circulating in the lobby. The source of the radiation was a hot spring that emanated radon. Patients soaked in irradiated water and inhaled radon directly through tubes. A few early studies had claimed that radium placed near tumors could shrink the tumors, so doctors at the time thought more was better. “It’s like the difference between treating something with a bomb and treating something with a scalpel,” says Kang.
Radon exposure is now known to be a leading cause of lung cancer. The invention of the Geiger counter in 1928 would help physicians better measure doses of the chemical, paving the way for medical breakthroughs that would enable radiation to be used for cancer treatments today.