Absinthe is an anise-flavored liquor or spirit that is made by steeping wormwood and other aromatic herbs (e.g., hyssop, lemon balm, and angelica) in alcohol. The liquor is a dazzling emerald blue-green color, due to its chlorophyll content, and is normally clear. It changes to a cloudy white when mixed with water. It has long had a romantic reputation due to its supposedly toxic qualities derived from the wormwood, caused by thujone, a component of an essential oil derived from wormwood (Artemisia absinthium).
Validation of absinthism
Recent research has shown this to be a romantic fantasy. 19th-century reports of thujone toxicity were based on concentrations of 260 mg/l. An analysis of the history of that level seem, in part, to be based on the assumption that there was a disorder of absinthism, it was caused by thujone, and the techniques available for analyzing thujone concentration overestimated its actual concentration. Studies in fruit flies and mice does demonstrate thujone affects the gamma-aminobutyric acid receptor, but, even in these cases, the mechanism of toxicity does not immediately seem to correlate with the reputed human effects. Admittedly, it might be hard to recognize rat or fruit fly suffering from delusions.
Commercial absinthes are made under a "thujone ban" requiring the concentration to be below 35 mg/l. It is not clear that this level has any firm relationship to demonstrable human effects, certainly not more than the 100-proof or more ethanol concentration of classical absinthe.
Thujone analyses of past and present absinthes
Analyses of 15 samples of pre-ban absinthe (i.e., before 1915) produced results varying between 0.5 and 48.3 mg/L, with an average concentration of 25.4 +/- 20.3 mg/L and a median concentration of 33.3 mg/L.
Is it possible that the thujone in these aged samples had degraded over time? Testing of contemporary commercial absinthe had either no detectable thujone or an amount well below the allowable level. Laboratory-prepared extracts using classical recipes had low concentrations (mean: 1.3 +/- 1.6 mg/L, range: 0-4.3 mg/>). 1930 vintage absinthe, made before the ban, contained 1.8 mg/l.  In other words, it was not possible to prepare a wormwood extract, without thujone suppression, that had much more than 10 percent of the current legal limit, and a small fraction of the alleged toxic level.
- Stephan A Padosch, Dirk W Lachenmeier, Lars U Kröner (2006 May 10), "Absinthism: a fictitious 19th century syndrome with present impact", Subst Abuse Treat Prev Policy. 1: 14, DOI:10.1186/1747-597X-1-14.
- Karin M. Höld, Nilantha S. Sirisoma, Tomoko Ikeda, Toshio Narahashi,John E. Casida (2000 March 21.), "α-Thujone (the active component of absinthe): γ-Aminobutyric acid type A receptor modulation and metabolic detoxification", Proc Natl Acad Sci U S A. (no. 8)
- Lachenmeier DW, Nathan-Maister D, Breaux TA, Sohnius EM, Schoeberl K, Kuballa T. (2008 May 14), "Chemical composition of vintage preban absinthe with special reference to thujone, fenchone, pinocamphone, methanol, copper, and antimony concentrations.", J Agric Food Chem. 56 (9): 3073-81
- Lachenmeier DW, Emmert J, Kuballa T, Sartor G. (2006 Apr 20), "Thujone--cause of absinthism?", Forensic Sci Int. 158 (1): 1-8