Most of these sources, including mycology references, list both A. muscaria and A. pantherina as "toxic", "poisonous", or even "deadly poisonous".1,2 At the same time, A. muscaria has been used for centuries as a shamanic inebrient and continues to have a small but consistent following as an entheogen.

At least some of the confusion comes from varying definitions and uses of the terms "toxic" and "poisonous". The traditional definition of a "poison" or "toxin" is usually something along the lines of "a substance that causes injury or death". But the terms "poisonous" and "toxic" are frequently used to describe any substance that causes physical illness, even temporary. There is no doubt that some people react to A. muscaria with nausea and physical distress. Even effects which are sought by some--loss of equilibrium, changes in perception, or sedation--would be considered undesirable by others, especially if they occurred unexpectedly.

This, in combination with the desire of most authors to limit liability when providing information about plants that are used recreationally, leads most field guides to use the term "poisonous" unequivocally for all plants which contain a psychoactive chemical. It doesn't take a genius to see the problems with this approach, as readers begin to associate the term "poisonous" with "recreational potential".

Because A. muscaria and A. pantherina belong to the genus Amanita, the same genus that contains two deadly, liver-toxic mushrooms (Amanita phalloides and Amanita virosa), many people believe that the fly agaric mushrooms also contain liver toxins. But the amatoxins and phallotoxins that are responsible for the deadly nature of A. phalloides, A. virosa, and several species of Galerina and Lepiota, and that cause a few deaths each year, are not present in A. muscaria or A. pantherina. At least some of the confusion around this issue stems from the name "amatoxin", which certainly suggests its presence in all Amanita species.

The primary active chemicals in both A. muscaria and A. pantherina are muscimol, ibotenic acid, and traces of muscarine.3,4,5 None of these chemicals are toxic to the liver at the doses present in these two mushrooms.6 And while it's not uncommon for a careless mushroom hunter to ingest A. muscaria and spend the night in the hospital--as they unexpectedly experience drowsiness, hallucinations and twitching--fatalities are few and far between. Children in particular seem prone to ingesting the beautiful red and white fungi, but as stated in a case report of eight children who had ingested A. muscaria, "recovery was rapid and complete in all patients."7

There have been only a few reported deaths related to A. muscaria, and these are generally cases of misidentification, where large quantities were ingested as food.8,9 Jonathan Ott reports in Pharmacotheon that he has only been able to verify two deaths, one related to A. muscaria and one to A. pantherina, and both were in elderly and infirm individuals. One unconfirmed report describes a man who was reported to have died after the ingestion of more than two dozen A. muscaria which he mistakenly thought were A. caesarea (an edible Amanita species).10

While it is probably good advice for the novice mycologist to avoid Amanita muscaria and Amanita pantherina because of the possibility of misidentification, this recommendation for caution should not be misread as evidence of the presence of liver toxins or a poisonous nature.

http://www.erowid.org/plants/amanitas/amanitas_info7.shtml