Milk Weed
The white sap from this common weed, also known as petty spurge, was described by Nicolas Culpeper's Complete Herbalist (1826) as "a good treatment for warts".
Don't try this at home, however, as its also an irritant.
Milkweed made its way from its native Europe to Australia, where biochemist Dr Jim Aylward had it in his garden.
"My mum grew it for 20 years and swore by it," he says.
"She always told me to put it on my skin to help sunspots."
In 1997, Dr Aylward isolated its active ingredient, ingenol mebutate, which he discovered was toxic to rapidly replicating human tissue.
And recent clinical trials of Picato, a gel derived from milkweed sap, suggest it is effective at stopping lesions turning into skin cancer
Leeches
Leeches were one of the more civilised methods of bloodletting, a popular cure for disease.
For the Ancient Greek physician Hippocrates, any imbalance in the four bodily "humours" (blood, black bile, yellow bile, and phlegm) would cause disease.
And the best way to correct this was to drain the excess - often blood.
Fast-forward to 1830s Europe, and bloodletting was big business.
Use of leeches to treat almost all ailments had reached its peak, with France importing about 40 million every year.
With the rise of "rational" science, and no evidence to back it up, bloodletting died out.
But recent advances in surgery mean leeches are back on the wards.
Hospitals such as UCLH in London use these bloodthirsty worms to drain excess blood after microsurgery, which helps to promote natural healing.
They can be used in postoperative care of skin grafts, or after lost fingers and ears have been reattached.
They produce a protein that stops blood clotting - and this gives tiny veins time to knit themselves back together.
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