Never eat a mushroom unless it is positively identified as edible. Mistakes can result in toxic reactions ranging from mild gastric upset to death. If in doubt, throw it out!
Eat only fresh mushrooms that are free from infestation by insects or larvae. Mushrooms can spoil, and eating any spoiled food can cause food poisoning or other adverse reactions.
Thoroughly cook all mushrooms unless they are specifically known to be edible raw. Some mushrooms contain toxins or gastrointestinal irritants that must be destroyed by cooking.
Eat mushrooms only in moderate quantities. Mushrooms are not easily digested; overeating them is an easy way to get sick.
When trying a mushroom for the first time, eat only a small portion [a spoonfull], and don't try any other new kinds for forty-eight hours. As with many kinds of food, some people are sensitive or allergic to mushrooms commonly eaten by other people. Individuals with known food allergies or sensitivities should be extra careful when trying mushrooms new to them, especially those species known to present problems for some individuals.
Don't pick mushrooms from contaminated habitats. These included polluted areas, chemically treated lawns, ornamental trees, and places close to highways, landfills, toxic waste sites, crop fields, power lines, railroads, buildings, industrial areas, or firebreaks. Contaminants may accumulate in wild mushrooms.
Never assume that a wild mushroom you find overseas is the same edible species you know from North America or vice versa. Too many serious cases of mushroom poisoning occur because vacationers and immigrants unwittingly gather dangerous look-alike species not found in their native lands.
Be conservative about feeding wild mushrooms to children, the elderly, and the infirm. Avoid edible species known to cause adverse reactions in some people, and don't let children, the elderly, or persons in poor health try an unfamiliar kind of wild mushroom until you and other friends or relatives have identified and eaten it without any adverse reactions. Limit portion sizes for children, the elderly, and the sick because they're generally more susceptible to toxins than other people are.
When trying a mushroom for the first time, save a few intact, uncooked specimens in the refrigerator for forty-eight hours. If someone develops an illness within two days after trying an unfamiliar mushroom, the physician may want expert identification to rule out the mushroom as the culprit.
Examine every specimen in every collection of mushrooms to avoid inadvertent mixing of different species. Even experienced mushroom hunters can err if they become careless and fill their baskets too hurriedly.