Toxic Fungi of Western North America

by Thomas J. Duffy, MD

Guidelines for pot-hunters

  1. Learn the known toxic fungi first and the genera in which the major poisonings are found— Amanita, Lepiota, Galerina, Conocybe, Inocybe, Clitocybe, Paxillus, Hypholoma, Psilocybe, Cortinarius and Gyromitra.
  2. Eat new edible fungi in small amounts at first.
  3. Be cautious offering wild fungi to guests even if you have had no problems. Idiosyncratic GI reactions are common, although typical allergies such as hay fever, asthma and hives are uncommon. There are no reports to date of mushrooms causing allergic (anaphylactic) shock.
  4. Remember that many mushrooms cause trouble when eaten raw. These are usually GI upsets. Gyromitrin and some other toxins are destroyed, at least in part, by cooking. The Europeans have found that, on rare occasion, a number of common genera including "edible" amanitas are able to provoke red blood cell destruction when eaten raw or partly cooked. This should be true of all western hemisphere “blushers” and of species referred to by the European name Amanita franchetii (Boud.) Fayod. (13a)
  5. Don’t be gluttonous. Small amounts of some toxins may be tolerated.
  6. If a canned mushroom has been ingested, call attention of physicians to botulism if there are pupil dilation, muscular weakness or central nervous system symptoms. There is an anti-serum available, which may keep victims off a respirator.
  7. Heed the advice of Elias Fries in his Observationes mycologicae—“Illustrations appeal to idlers who do not have energy enough to study descriptions”. (16) Using a poor photograph of Agaricus augustus, but not reading the description below the colored plate, two California victims misidentified what was actually Amanita phalloides. Both required liver transplants.
Agaricus augustus
Agaricus augustus photo © Michael Wood