It has been said that absinthe makes people go mad, blind, epileptic, and apparently it could even infect you with tuberculosis or turn you into a criminal.
This is all nonsense, of course, but there has to be a reason why that many people believe in those myths. Absinthe was very popular in the 1800s. There was a broad range of different absinthes available – some where sincere, honest products, some were cheap, badly made products that shouldn’t even have entered the market. They were made with methanol and were seriously dangerous for the human body. A similar problem was caused in the United States during Prohibition. Unregulated and untested alcohol can lead to serious problems when people take advantage of the situation for profit.
Determining between toxic, cheap and often dangerous copies of absinthe and true absinthe must have been extremely difficult for both the society and the government of the 19th Century. However, real absinthe, consumed moderately of course, is only as harmful as any other alcoholic spirit.