My complete (warning -it's a 21 megabyte Powerpoint) guide to mushroom poisonous identification and treatment is available online.
There are three basic types of patients who I treat via Regional Poison Control Centers referrals:
1. Toddlers - 2 to 4 year olds wander out to the lawn and munch a mushroom. They usually eat small quantities and most often parents find unchewed pieces in their children's mouths. Common mushroom types are the Fairy Ring pictured above (Marasmius oreades) and "little brown mushrooms" (Mycena), both non-toxic. I generally try to avoid treating toddlers with activated charcoal, the common treatment for poisonings, by rapidly identifying the mushroom as non-toxic. My experience with activated charcoal in pediatric poisoning is that more charcoal ends up all over the parents than in the patient.
2. Teenagers - 14-18 year olds who search cow pastures looking for blue-staining mushrooms i.e. "Hey man, do THOSE shrooms grow around here?" Yes, various hallucinogenic mushrooms grow in New England - Psilocybe species, Panaeolus, and Amanita Muscaria abound. The challenge for these teenagers is that these mushrooms contain wildly variable amounts of toxins. One mushroom may contain virtually no toxin and another may contain an overdose. I remind teenagers that "intoxicate" contains the word "toxic". The treatment for overdose of hallucinogens is largely supportive - a quiet dark place and the use of anti-anxiety drugs to treat a truly bad trip.
3. Gourmets - the 20+ educated amateur mushroom hunter with an Audubon field guide who looks for mushrooms based on pictures in the book. There are 2500 species of mushrooms in North American, of which 35 are great to eat and a dozen are lethal. Edible mushrooms and toxic mushrooms can look similar. A mushroom expert considers the time of year, where the mushroom is growing, and trees growing near the mushroom when picking edible mushrooms. A photo from a field guide is really not that helpful. The only deaths I've had in my consulting practice are the Gourmet amateur mushroom hunters. A typical story is that an educated person picks two pounds of wild mushrooms, makes stroganoff, gets ill 12 hours later, waits a few days, feels better, then suddenly develops seizures, liver failure, kidney failure and seeks medical care. By that time it's too late and not even liver transplant works. If you want to pick mushrooms to eat, learn from an expert how to identify a few key species such as morels, chantrelles, and porcini. Learn where they grow and pick them from the same patch year to year. Avoid eating any mushrooms with white gills (the underside of the cap). Not all white gilled mushrooms are poisonous, but Amanitas are white gilled mushrooms that can kill you.
How am I consulted? Today, I've received 4 consults already. Doctors throughout New England call Poison Control Centers, which refer callers to me. The doctors use their cell phones to take pictures of the mushrooms and patients, then email them to me. On my Blackberry, I can view the mushroom, determine the species, outline a course of treatment and followup with the patient to ensure all is well.
Mushroom Season runs from June to October in New England. Based on the volume of incoming consultants, I can tell it's going to be a busy year!