The mind of a wizard is more open to the more esoteric elements of his surroundings Ã¢â?¬â?? this is why he is able to perceive the weave of the Great Tapestry that is the multiverse, and pull at the strings. This increased sensitivity can manifest in several ways.
Actually a real-world fungus, just heard about it. A fungus that tastes well and all, no ill effects. UNLESS you consume some beverage, even 3 (three) days after eating it. Then you become really sick, pains, vomiting, all the fancy stuff. Was really used to cure alcoholism. May be a joke or to make sure the heroes spend their time focused on the mission.