Some of the best cheeses in the world are aged — it wouldn't be blue cheese without the mold, nor brie without the white rind, or Parmesan without 10 months of maturation. However, there's a big difference between properly aged cheese and cheese that has expired; here’s how to tell the difference and protect your health.

Like any expired food, eating cheese that has gone back can cause food poisoning and/or other gastrointestinal issues. Generally speaking, if you find a bit of mold on hard cheese, you can cut the moldy part off and safely consume the rest; for soft cheese, the mold cannot be thoroughly removed, so it isn’t worth the risk.

If there's an extensive amount of mold, it has likely fully contaminated the cheese and you should toss it. It's difficult to tell if some cheeses have gone bad, and not all changes in your cheese mean spoilage; warning signs besides mold include a "barnyard" or ammonia-like odor, an "off" taste, or a burning/tingling sensation in the mouth.