Thujone is the active component found within wormwood (Artemisia absinthium) and is therefore present in absinthe as well. The reported psychedelic effects that surrounded absinthe in earlier times were originally thought to be the product of this chemical. However more recently research has shown that the levels of thujone present in traditional absinthes were much smaller than was previously thought.
The level of thujone that is legally allowed to be present in food and drink is regulated in most countries. For the absinthe renaissance to have ever been feasible, the setting of these regulations was a crucial event. This important breakthrough was achieved by George Rowley (brand owner of La Fée, owner of BBH). On 21st July 1998 a document that he had drafted, written and signed used data from a test on some absinthe samples he had had conducted by VSCHT of Prague University to show without a doubt that the samples fell within the legal limits established in 1988 in EEC Council Directive No. 88/388/ECC.
This work was crucial as it was the first time this directive had been applied to absinthe and it became the benchmark for all other absinthe producers to follow. The maximum amount of thujone allowed in the directive for spirits which contain over 25% ABV is 10 parts per million (with bitters or amers containing up to, but not more than 35 parts per million). This was then used as a benchmark by a large number of governments globally when setting their own thujone limits.
The effect of absinthe on drinkers is commonly reported as creating a clear headed mood, one reason why it was so popular with so many artists and writers. This is most likely to be a result of the combination of different herbs used in making absinthe, many of which have been used as herbal remedies for centuries. As the myth of thujone and its psychedelic properties has been effectively debunked, the most obvious explanation for any crazed effects arising from the drink must surely be the fact that absinthe is high in alcohol and if drunk irresponsibly can lead to extremely high levels of inebriation.