Wormwood - the plant
Mediterranean perennial herb or shrubby plant (Artemisia absinthium) of the family Asteraceae (aster family), often cultivated in gardens and found as an escape in North America. It has silvery gray, deeply incised leaves and tiny yellow flower heads. Wormwood oil has been utilized since ancient times as an insect repellent, particularly for moths; until recently it was used for intestinal worms and for other medicinal purposes. It was also employed in brewing but is best known for its bitter principle which is an important ingredient of absinthe. Because of its bitter taste the common wormwood has long symbolized any rancor felt by man and is often so represented in the Bible. Other artemisias, some American, are also called wormwood; still others include southernwood (A. abrotanum), tarragon, silver king Artemisia (A. albula), old woman, or dusty miller (A. stelleriana), Roman wormwood (A. pontica), sagebrush, and the Levant wormseed (A. cina), which yields santonin. Wormwood is classified in the division Magnoliophyta, class Magnoliopsida, order Asterales, family Asteraceae.
Wormwood and thujone
Thujone is the so called "active ingredient" in wormwood oil.
Thujone - chemically speaking
Alpha-thujone, has a similar molecular structure to menthol, a-pinene, eucalyptol, camphor and other monoterpenes. Formerly believed to have a THC (cannabinoid) structure-activity relationship and mechanism, a-thujone is now known to modulate only an entirely different receptor site, the GABA (gamma-aminobutyric acid) system. GABA moderates the firing of neural synapses; a-thujone mildly antagonizes such inhibition.
Thujone levels in modern absinthe
Inside the EU there are regulations stating that commercial absinthe may contain up to 10 mg/kg thujone. Many modern brands produced both within the EU and outside, state that they have very high Thujone levels. Something that can never be controlled and confirmed by the general public. Most modern reproductions contain merely no thujone at all. The claims of high thujone levels are mostly for boosting sales. Either way, the thujone level in an absinthe is in no way detectable through taste. Bitterness come from wormwood, not thujone.
Thujone levels in vintage Belle Epoch absinthe
It is often stated that the absinthe produced in the 19th century had much larger amounts of thujone present than are allowed in today’s versions of the drink, which have to comply with EU limits of 10 mg/l. Values as high as 260 mg/l have been quoted by Arnold (Absinthe, Arnold WN, Scientific American, 1989 Jun, 260(6):112-7). However analytical techniques available in the 19th century were not capable of separating thujone from many of the related compounds present in the essential oils of the plants used to make absinthe and it is therefore likely that concentrations were grossly overestimated.
Analysis of thujone levels in vintage and modern absinthes
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Wormwood and Thujone in other alcoholic drinks
Thujone, or traces of thujone, can be found in many other drinks as well. Other bitters, such as Vermouth, Gammel Dansk and the extremely bitter Swedish Beska Droppar (translates to; Bitter Drops) all have wormwood as their main ingredient. Vermouth is actually German for wormwood, and that alone states the content. The odd part here, is that none of these were ever banned anywhere in the world. And no where have there been reports of people suffering from neurological side effects from the wormwood in these, at least no other than plain old alcoholism.
Thujone in our every day life
alpha-Thujone is actually an important component in salves, perfumes, creams, etc. mainly as a counter-irritant. Many over-the-counter products contain thujone, such as Vap-O-Rub. Also, White Cedar - commonly used against moths in wardrobes and chests gets its anti-insect effect from the thujone in the wood. What most people don't know is that thujone not only occurs in wormwood, but also in many common culinary herbs such as Sage, Tansy and Tarragon. And as far as I know, no one has ever suffered from heavy neurotoxical effects from eating food containing any of those.
Conclusion...
In some absinthes there are thujone to some extent. In most absinthes there is virtually none. The thujone in the absinthe is not detectable by taste and it will neither kill you, nor get you high. Extremely high intakes of thujone can cause convulsions etc, but before reaching those levels of thujone, you will have passed out or died from the amount of alcohol. The "secondary effects" of thujone have never been proven. However, many say they experience a different kind of drunkenness from absinthe. Some call it a sort of clarity or higher state of consciousness. But if this would be from the supposed presence of thujone, the same effect would be obtained from drinking vermouth or for instance "Beska Dropppar", and I for one know that's not true! To my own belief, much of this is a psychological effect, and to some extent I believe it is also due to the mix of the many other herbs contained in absinthe. However, most commercial reproductions contain only oil mixes and essences. One must never forget that we're dealing with a spirit with 55-70% alcohol! The level of thujone in an absinthe has nothing to do with the quality of the drink and one can be quite sure that a brand that states to contain very high levels of thujone, does so only to boost sales and make money from bad, cheap products. However, in a recent lab test and scientific study it was shown that Versinthe La Blanche, contained the highest level of Thujone among the tested brands, a mere 5.4 mg/l. This leaves us with the fact that neither wormwood, nor thujone is the devil. But then, why was absinthe banned? That is another thing, and that can be read in the "sticking to the facts" section.
Sources and references for the information found here, come from; InfoPlease.com, AbsintheOnline.com, Molecules of the Month (University of Oxford).