Erethism or erethism mercurialis is a symptom complex of mercury poisoning, presenting with excessive shyness, timidity and social phobia.[1][2] This was common among hat makers of old England who used mercury to stabilize the wool in a process called felting. The character the Mad Hatter in Lewis Carroll's Alice in Wonderland is often believed to be an example of someone suffering from erethism, but this account is apocryphal. The character was almost certainly based on Theophilus Carter, an eccentric furniture dealer who was well known to Carroll.[3]