A childhood belief about nasty food

I once worked with a man, who though he was in his late '30's still lived with his mother. One day at lunch he completely flipped out. He had found a spot of mold on the bread of his sandwich, and thought it was a lethal poison. He had never seen moldy bread before, and thought someone was trying to kill him. We calmed him down eventually, but we were a little traumatized, too. We thought he was a little weird before, but the 'mold incident' really blew our minds.