Medical history has seen humans try their hands at all kinds of peculiar cures to tackle deadly diseases (even Isaac Newton was at it with these toad-vomit lozenges for bubonic plague). While the modern phrase "first do no harm" feels as if it's been ignored at certain points in history, it's also true that early doctors were trying to preserve life, even when their treatments turned out to be fatal.

The fascinating story of questionable cures is explored in a new book by medical historian Dr Lindsey Fitzharris and caricaturist Adrian Teal called Plague-Busters! Medicine's Battles With History's Deadliest Diseases. We caught up with them at CURIOUS Live – IFLScience's free festival of science – to find out more about it.

Which of history’s deadliest diseases are you most relieved to have avoided?

Dr Lindsey Fitzharris: For me, it's always going to be smallpox. Just one teaspoon of the smallpox virus is enough to kill every man, woman, and child on the face of the earth. It was a terrible disease. It was really disfiguring as well. It is the only human disease that we've ever eradicated which is an incredible accomplishment for medicine.

Adrian Teal: For me, it's scurvy. The reason I am both fascinated and appalled by scurvy is that I have a real fascination with maritime history. And of course, it affected sailors a lot throughout history. Unlike a lot of the diseases in this book like the black death and smallpox, it would take weeks or sometimes months to kill you.

We now know it was a vitamin C deficiency [causing] your body to break down because it can't create collagen, which is the stuff that knits us together. Horrible things happen your teeth, your gums swell up, old wounds, old scars, maybe you broke your arm 20 years ago, and suddenly, your bones start breaking themselves again. Old wounds will open up and start bleeding. It's really horrific, and it takes a long time to kill you. So to me, that's the most awful death I can imagine.

What are some of the worst “cures” you came across in your research?

AT: One that I find really quite bizarre [that was] harmful to the point of actually killing people was a cure for rabies in the ancient world. Another word for rabies is hydrophobia, which means fear of water because people who get it can't face swallowing water to the point where they're actually terrified of water coming near them. That's why animals drool and froth at the mouth when they've got rabies, because they can't swallow.

So, in the ancient world, the idea was, “Well, let's get water into these people somehow. If we hold them underwater, then they will take water in while they’re being held in the bottom of the pond,” or whatever. Which was unfortunate, because they didn't really distinguish the difference between swallowing water, taking it into the stomach, and taking it into the lungs and drowning. I suppose killing people by drowning was one way to "cure" rabies, it would cure a lot of other things.

LF: [You] should know that rabies is 100 percent fatal if left untreated. So, I guess, in a weird way, they were they were speeding up the inevitable…

Any other weird and harmful practices?

LF: I always think bloodletting is one of the most harmful practices from the past. It persisted into the 20th century, it's kind of like the equivalent of going to your doctor and asking for antibiotics, people requested to be blood-let. The idea in earlier periods was that if you got sick, there was an imbalance that had to be corrected, perhaps you were producing too much blood. So, they would release the blood and hope that that would cure you.

The first President of the United States, George Washington, fell ill with an upper respiratory infection in the late 18th century. And he called for the blood letters, and they came, and they let so much blood out of George Washington that it hastened his death. Now, it's likely he probably would have died anyway, but it certainly didn't help letting all that blood out.

As well as deadly “cures”, there are some really peculiar examples in Plague-Busters! – do you have a favorite?

LF: A lot of people were unlikely to go to a hospital surgeon to see a doctor [because] that was very expensive. So, they [would] turn to these folk remedies and one of my favorites is the “madstones”. This became very popular in the mid-19th century in America, and they were like these big hairballs that were created in the guts of goats and deer.

People thought that they could draw out rabies and poison and, in fact, this was such a widespread belief that the President of the United States, Abraham Lincoln, took his son to be cured by a madstone when he thought that he had been bitten by an animal that was quite possibly rabid.

AT: While we’re on rabies, one of my favorite bizarre cures is in the Middle Ages, there was a monk called Albert the Great who thought that if you had a rabid dog, chances were you were going to get rabies because the dog was going to bite you. So, the best thing [was] to cure the dog of rabies and he thought the best way to do this was to hang it upside down in a bath of water by its paws.

After a while, you cut it down, you shave it, and then you rub it with beet juice. So, what you end up with is a savage, naked, bright pink dog – so if the dog wasn’t angry and going to bite you before all of this, it sure as hell was going to afterward.

Were there any weird cures that actually turned out to have some merit?

AT: There's a really good one to do with smallpox. It didn't actually cure smallpox, but it did have a vaguely beneficial effect. The idea was that if you had smallpox, you should surround yourself with anything red. So, for instance, Queen Elizabeth the first of England, when she had it, she was told to completely swaddle [herself] in red cloth. Other people were supposed to sleep in red rooms, with red drapes, and red curtains, eat red food under red light. Just surround yourself with red.

Now, in the 19th century, there was a Danish scientist who discovered that red light actually can be beneficial in terms of helping you to help you stop the scarring that you get from smallpox. Because, if the red light penetrates the skin enough, it will promote collagen, which – as with scurvy – is the stuff that holds us together.

So it will stop the pustules from weeping and actually prevent scarring. And in some respects, apparently, it can help with inflammation and even tackle some kinds of bacteria. So purely by chance, the 14-15-16^th-century, people doing this, were actually having beneficial effects on their patients without having the first clue why it works.

LF: I always think of the iconic plague doctor. The plague doctor wore this beak and the idea behind it was that they thought disease was caused by something called miasma, which were like bad odors, and it's understandable because the slums and these overcrowded areas in earlier periods, they would have smelled very bad. They would have been very disease-ridden.

The doctors thought that the miasma was what was spreading the disease, so they wore these masks, and they would put sweet-smelling herbs into the bottom of the beaks [thinking] this would protect them from miasma. They would cover themselves head to toe, wear gloves, and so inadvertently, they were probably protecting themselves – for very different reasons to how we understand diseases spread today – but nonetheless, it would have had a similar effect.

What about some of history’s deadliest diseases that we have cured?

AT: I don't mean to go on about scurvy, but the thing about scurvy is that actually, the problem was solved quite early on in the mid-18^th century by a really conscientious Scottish doctor called James Lind.

He discovered, after a long process of experiments, that [the cure] would be citrus juice because it's a vitamin C deficiency. Now, that's great and that solved the issue from a scientific point of view. But just because you've solved the problem, it doesn't mean the problem is solved, because his work wasn't widely known.

He published it, but the book wasn't widely distributed. It actually took probably another generation before anybody took a look at his idea. So, what I love about medical history is you get these successes, but often the successes can still be flipped back into failures.

LF: Absolutely. In fact, we start Plague-Busters! with a story of a physician named Ignaz Semmelweis. He was a surgeon and physician practicing in Austria in the 19th century and he was putting together this idea that doctors were coming from the morgue, they were coming from the “dead house” onto the birthing wards, and these mothers were dying of high infection rates as a result.

He guessed that they were carrying some kind of poisonous matter onto their hands. So, he was trying to convince his colleagues to wash their hands, something that's really basic today that we know helps with hygiene and hospitals, but his colleagues just were not having it. They called him the “hand washer”, and he called them murderers.

It escalated from there, until they put them into an insane asylum, and he died. And so Semmelweis never got to see his own theories vindicated. And this is really the story of the history of science and medicine, it can be slow to change. And, you know, one of the lessons I think, is that we always need to be open to those creative solutions to these problems. Even those things that seem kind of bizarre and out there can be proven after a long time to be true.

You can watch the full interview on YouTube or order your own copy of Plague-Busters! today.