Its not a silly question funnygirl, and it is one of much debate. The simple answer is that mushrooms (assumed edible) cooked or raw can affect many people in many different ways.
Many hydrazine�s are known to be strong carcinogens and can be found in a lot of edible mushrooms. Cooking destroys some or all of the hydrazines, but the steam (ammonia like) given off during cooking has been known to make some cooks ill. Besides this fact, the structural material or cell walls in a mushroom is made of chitin, and humans don�t have the ability to digest this derivative of cellulose.
The body can do several things to this undigested chitin. It can expel it by vomiting or send it the other way with diarrhoea. Small amounts may pass through the gut with other food and go unnoticed, or it may stay in the gut where bacteria will work on it causing bloating, gas, and other discomfort. Cooking does not destroy chitin but may ease its effect - this is where some people may experience some very unpleasant symptoms.
Some chitin is good for you, and mushrooms have many nutritional benefits. Crabs, beetles, worms and mushrooms contain large amount of chitin. Often, insect coats contain thick, stiff layers of chitin.
It really just depends on your preference for eating fungus, raw or cooked and your body�s reaction to that consumption.
Oodles of garlic is the only known remedy. Or at a push, 3 raw onions.