“As mad as a hatter” – this is a well-known English idiom, particularly famous after Lewis Carroll created the Mad Hatter character in his work Alice in Wonderland. However, what is less known is the fact that this idiom is based on actual events.
In the 18th and 19th centuries, hatters used mercury to treat felt (traditionally made from rabbit fur or the more luxurious beaver fur). Unfortunately, mercury is a highly toxic heavy metal, which causes severe damage in the human body. In the case of mercury poisoning (also known as Minamata disease or the Mad Hatter disease), it infiltrates neurons to cause severe neurological symptoms. For example, it can impair vision and hearing, cause paresthesia (pins and needles), anxiety, depression, tremors and hallucinations. The famous physicist, Isaac Newton, also suffered from Mad Hatter disease.
Another mad character from Alice in Wonderland is the March Hare. As one may deduce from his name, he is modelled after a normal hare. The reason why the March Hare is mad is that March is around the time when rabbits enter their mating season, and male hares are in heat. They then have only one thing in mind: sex.
Maybe, as the Cheshire Cat explains, “we’re all mad down here”.