system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it okay to eat blue cheese, but not other things that are moldy?
gpt
Different species of mold have make different byproducts as they grow, and not all of them are harmful. Through experience we know some that are safe, like those used in making cheese. (Yeast is also a fungus, but not a mold, and is used for baking and brewing.) When food around the house gets moldy from whatever spores were in the air, it's a bad bet: there's a big risk that whatever mold it is either is generally poisonous or might produce something you're allergic to.

This why cleanliness is actually very important when working with mold. Get the wrong kind of fungus in your product and it will ruin the whole batch.