Erethism
Neurological disorder from mercury poisoning, historically affecting hat makers.
Erethism, also known as erethismus mercurialis, mad hatter disease, or mad hatter syndrome, is a neurological disorder affecting the central nervous system, resulting from mercury poisoning. It is characterized by behavioral changes such as irritability, low self-confidence, depression, apathy, shyness, and timidity, and in extreme cases, delirium, personality changes, and memory loss. The condition has historical significance due to its prevalence among felt hat makers, who were exposed to mercury vapors during the felting process.
- field
- Neurological disorder / Occupational disease
- cause
- Mercury poisoning (inorganic mercury, mercury vapor)
- known_for
- Behavioral changes, tremors, and association with hat makers
- historical_population
- Felt hat makers (hatters) in England, France, and the United States
- alternative_names
- Erethismus mercurialis, mad hatter disease, mad hatter syndrome, hatter's shakes, Danbury shakes
Lore & Background
Erethism was historically common among felt hat makers in England, who were exposed to mercury vapors used when stabilizing wool during the felting process. This occupational exposure gave rise to the expression 'mad as a hatter.' In the 19th century, inorganic mercury in the form of mercuric nitrate was commonly used in the production of felt for hats, particularly during the carroting process. Hatters who came into contact with vapors from the impregnated felt often worked in confined areas. The use of mercury in hatmaking is thought to have been adopted by the Huguenots in 17th-century France, and the process was carried to England at the end of the 17th century following the revocation of the Edict of Nantes.
Reader's Guide
Erethism's significance lies in its role as a classic example of occupational mercury poisoning, highlighting the dangers of industrial exposure before modern safety regulations. The condition prompted several popular names, including 'mad hatter disease' and 'Danbury shakes,' the latter referring to hat makers in Danbury, Connecticut. The character the Mad Hatter in Lewis Carroll's Alice in Wonderland is sometimes believed to be an example of someone with erethism, though the origin of this account is unclear; the character was almost certainly based on Theophilus Carter, an eccentric furniture dealer. Today, erethism from hat making is no longer an issue, but it persists in other high-risk occupations such as chlor-alkali factories, dental clinics, and gold and silver mines. Biomarkers for measuring mercury exposure include blood, hair, nails, and urine, with urine being the ideal biomarker for chronic occupational exposure.
Did You Know?
- Erethism is also known as mad hatter disease, hatter's shakes, and Danbury shakes.
- The expression 'mad as a hatter' arose from mercury poisoning among felt hat makers in England.
- Mercury in urine has a half-life of weeks to months, making it the ideal biomarker for chronic occupational exposure.
- The character the Mad Hatter in Alice in Wonderland was almost certainly based on Theophilus Carter, not a hatter with erethism.
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