Maybe you hosted a nice little soirée with your friends and drank too much wine, or maybe you fell asleep on the couch while working on your night cheese. Either way, you've gotten up this morning and found a block of cheese sitting on your kitchen table, and now you're wondering, "Is this cheese still safe to eat? How long can cheese stay fresh unrefrigerated, and will I get sick if I eat cheese that's been left out overnight?" Unrefrigerated cheese happens to the best of us, and the good news is that though you should store cheese in your fridge, you'll probably be able to still enjoy cheese that's been left out overnight.
"Leaving cheese out overnight may impact the quality of the product, but would not—in most cases—result in a food safety issue," explains Adam Brock, director of technical services at Wisconsin Milk Marketing Board. If anything, there's a good chance you're over-refrigerating your cheese. "All cheeses, besides fresh cheese, should be served at room temperature for optimum flavor," says Brock. Fresh cheeses include burrata or fresh mozzarella, and they should be chilled until ready to serve. But soft cheeses like Brie or Camembert will both taste stronger and be easier to spread if given a chance to come to room temperature, and firmer cheeses will be easier to cut.
All you need to do to is take your cheese out of the fridge about an hour before you plan on serving it or using it. Though it's unlikely you'll face food safety issues if you leave cheese at room temperature for too long, for best quality, you should return it to the fridge after about two hours.
If you're still squeamish about leaving cheese out at room temperature, or eating cheese that's been left out overnight, stick with hard cheeses. "Cheeses that have been aged a bit longer, such as Parmesan, will be better able to maintain their unique flavor [and] functionality characteristics and are less of a food safety risk even when held outside of ideal conditions," notes Brock.
Soft cheeses, on the other hand, hold more moisture and so are friendlier to bacterial growth. (Sound gross, sure. But remember that soft, ripened cheeses are made with the help of bacteria.) So if you're being extra cautious, follow the USDA guidelines that recommend you toss perishable foods, including soft cheese, that have been left out at room temperature for longer than two hours. But as Brock notes, "There is always the potential risk of pathogens or mold, but the risk is minimal with most cheese that are manufactured under safe conditions." If you see mold on soft cheese, however, throw it out immediately.
So go ahead and eat that leftover Brie for breakfast. We won't judge you.