Many 19th century dyes contained poisonous ingredients such as arsenic.
Green dye was popularly associated with arsenic poisoning, though other dyes could contain it as well.
See:
https://thepragmaticcostumer.wordpre...ictorian-life/
"Stockings, on the other hand, were a bigger problem than dresses. Many contained more arsenic than dress goods and since they were worn directly on the skin, they led to far more illness."