Mad as a Hatter? Mercury Poisoning in the hatting industry

A combination of steam, sulphuric acid, mercury and other chemicals were used in the shaping and stretching of the felt used in hat production.

Unfortunately the fumes from the mercury (usually mercurous nitrate) often lead many hat factory workers to suffer from brain damage; hence, some believe, the phrase ‘Mad as a Hatter’.

Specificly, mental symptoms of mercury poisoning included loss of memory, depression, anxiety, and other personality changes; physical ones include trembling (known as hatter’s shakes, a loosening of the teeth, loss of co-ordination, and slurred speech. Mercury poisoning was a cumalative poison which also damaged the kidneys. If the prolong poisoning progressed to high another levels the sufferer could also experience psychotic symptoms such as hallucinations. Mad Hatter Syndrome is still often used to refer to the symptoms of mercury poisoning.

Lewis Carroll’s ‘Mad hatter’ in Alice in Wonderland appeared in 1865, by which time the phrase was already well known; Carroll did not invent the phrase. There is also not definitive proof that the phrase originated from the hat industry either,

The origin of the proverbial expression “mad as a hatter” is uncertain. It may derive from:

• Robert Crab, a 17th century eccentric who gave all his goods to the poor and lived on leaves and grass.
• Mercury poisoning suffered by many hatters in the 18th century and 19th century, when mercury was used in the manufacture of felt. Absorption of mercury through the skin can cause Korsakoff’s syndrome. These hatters so afflicted were also known as mad hatters
• An adaptation of the Anglo-Saxon word atter meaning poison, closely related to the word adder for the poisonous Crossed Viper. Lexicographers William and Mary Morris in Morris Dictionary of Word and Phrase Origins (1977) favour this derivation because “mad as a hatter” was known before hat making was a recognized trade.

Hatter - Wikipedia