Is It Safe to Eat Food That’s Been Sitting Out for Several Hours? 

We’ve all been there: you’re having dinner, get distracted by the evening chaos, and, before you know it, what’s left of your lasagna is now lukewarm. But is it still safe to eat? How about that pepperoni pizza that’s been out all night? Will reheating it make it salvageable?

To find out, we’ll look at how, why, and when bacteria grow on food, and how to know whether food should be tossed or not.

How Long Can Food Sit Out Before It’s Unsafe?

Whether food is unsafe depends on how long it’s been sitting out at room temperature. According to the United States Department of Agriculture (USDA), perishable foods that require refrigeration should never be left out for more than two hours.

Your best bet is to keep hot foods hot (that is, above 140 degrees Fahrenheit), and cold foods cold (below 40 degrees Fahrenheit). When foods sit out at temperatures between 40-140 degrees Fahrenheit, bacteria begin growing rapidly. That’s why this temperature range is called the “danger zone.”

Your best bet is to avoid leaving cooked meals out at room temperature for longer than the recommended time. Place them in the fridge as soon as you can.

Keeping an instant-read thermometer readily available is always a good idea, especially if you’re serving foods buffet style. From temping meats to checking on casseroles, having one of these in your kitchen will make serving and entertaining a little less stressful.

Which Foods Are Perishable?

Perishable foods are those with a short shelf life that will make you ill if you consume them after they spoil. For many perishables, it’s best to keep them at 40 degrees Fahrenheit or frozen. Refrigeration helps to slow down the growth of bacteria, which is why many foods—like meat, fish, and dairy—need to remain cold to stay fresh and safe.

Canned foods are sterilized and sealed in an airtight container to preserve them, which is why they’re considered nonperishable. According to the USDA, until you’ve opened a can, it can remain safe indefinitely.

The “sell by” date printed on the can indicates how long the food inside will keep its quality. So, while that can of corn might safely last 10 years, it probably won’t taste very good for that long. Just be sure to store canned foods in a cool, dry place and discard any dented or damaged cans.

Will Reheating at a High Temp Make Food Safe Again?

Some might think that reheating previously cooked foods at a high temperature will kill any bacteria present in food that has been left out. Unfortunately, this isn’t true, and the misconception could make you very ill.

While reheating leftovers that have been stored properly is perfectly fine, anything that’s hit the danger zone can be risky to eat. Some bacteria—mainly staphylococcus—produce harmful toxins, which are tough to kill. Even the highest of temperatures won’t destroy staph.

There’s a very helpful saying in the food safety world: When in doubt, throw it out. There’s just no reason to eat something if you have any reservations about its safety. Food poisoning is no fun, and it can even be life-threatening in some cases. So, save yourself a trip to the ER—don’t risk eating something that might be funky.

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With the holidays around the corner, lots of us will likely find ourselves serving or enjoying a buffet-style meal. No one wants to be responsible for making a friend or family member—or themselves—ill. Following these tips will ensure all your casseroles and roasted dishes are safe for everyone to enjoy.