Mad Honey, more scientifically known as grayanotoxin, is a toxic substance humans have been dealing with for thousands of years.
The way how it is created is quite simple. A bee takes nectar from a toxic rhododendron plant (available in Turkey, the United States, British Columbia and the UK). The toxic substance is then deposited at a beehive.
The odds of getting any ill-effects from this substance, from the honey at your local grocery store, are pretty much nill. By the time commercial honey is diluted the amount of material from a rhododendron is extremely low or non-existent.
However, if you buy honey from a local beehive that happens to be near a large amount of rhododendron, the risk goes up.
Mad Honey Versus the Roman Legions