Mushrooms can sprout anywhere. Lawns are moist and nutrient-rich and there's likely to be plenty of decaying matter underneath the grass. These are the perfect conditions for mushroom growth. The mushroom part of the fungus is the fruiting body; it contains more spores for mushroom growth.
Masses of hyphae---comparable in function to plant roots---are called mycelium and they spread underground. Mushroom spores are carried on the wind. This makes mushroom control at the source rather difficult if harsh chemical control isn't an option. The easiest way to control lawn mushrooms is to pluck them out of the ground when they appear and toss them in the garbage or the compost pile. Because you don't know if they're poisonous or not, be sure to wash your hands thoroughly after handling mushrooms.
If you suspect that your child has eaten a mushroom from the lawn, the first thing to do is call Poison Control. Call 1-800-222-1222 from anywhere in the United States. Look for symptoms of poisoning, such as gastrointestinal upset, which may include vomiting and stomach aches. A child who is drowsy or confused may have consumed a poisonous mushroom. Without medical treatment, these rather benign symptoms can become permanent heart, liver or kidney damage, according to the Children's Hospital of Philadelphia. Remember there is no cure for mushroom poisoning.
Death caps kill more people each year in the United States than any other mushroom. They belong to the genus Amanitas. Death caps present the same symptoms as other less deadly mushrooms when eaten. Symptoms dissipate after a few days, then return with a vengeance, damaging the kidneys, heart and liver and ending in coma and death. Death caps do not look, smell or taste all that different from other mushrooms.