Mold grows on cheese when it is placed in a badly ventilated or moist area. Mold spores are airborne all around us, invisible to the naked eye. And if one spore makes it onto a piece of cheese, it can begin to reproduce rapidly and feed off of the cheese. Click to see full answer.
Mold generally can't penetrate far into hard and semisoft cheeses, such as cheddar, colby, Parmesan and Swiss. So you can cut away the moldy part and eat the rest of the cheese. Cut off at least 1 inch (2.5 centimeters) around and below the moldy spot. These molds are safe for healthy adults to eat.