Can I Eat Food That Sat Out All Night?

Ah, friends. They're like family but cooler. Fully customizable. Fall and one of them will be right there to pick you back up. But as great as friends can be, they also do a lot of really stupid stuff. Stuff that blows your mind. Like, sometimes it seems crazy that you even hang out with people who make such crappy decisions. Stuff that, were it to get out, would be mortifying for anyone with even a shred of self-respect. Lucky for your friends, they've got you to ask their deepest, darkest questions for them. And lucky for you, we started this column to answer those most embarrassing inquiries.

The Scenario: After a long night at the bar, and possibly a few too many drinks, your friend makes it home in time to order a pizza. In a tipsy state, he eats a slice (or three), leaves the box on the counter, and passes out. When he wakes up the next day, nothing sounds better to his pounding head and queasy stomach than another slice of greasy pizza. So he grabs one from the room-temp box, heats it up in the microwave, and chows down.

The Concern: The general rule of thumb when it comes to food safety is that hot food should stay hot and cold food cold. Keeping perishable food out between 40 and 140 degrees is what's known as the "danger zone," explains Archie Magoulas, food safety expert with the USDA. With room temperature being around 70 degrees, that's the prime temperature for bacteria to grow and multiply.

He says cooked food should be left out for no longer than two hours, so a pizza sitting out at room temperature all night instead of being properly refrigerated has a higher risk of being contaminated with bacteria that can lead to food poisoning.

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The Worst That Can Happen: Although all perishable food has a risk of being infected with bacteria if it's not properly refrigerated or cooked, it's even riskier with food that's been handled by other people—say, the pizza shop employee who was in charge of tossing your pie. Severe bacteria, such as Staphylococcus aureus, has more of a risk to grow and multiply.

"Staph aureus can produce enterotoxins, which can give you significant gastroenteritis in the matter of a half hour to four hours," says Philip Tierno, professor of microbiology and pathology at NYU School of Medicine. With gastroenteritis (the fancy term for the stomach flu), the symptoms are the particularly unpleasant kind we typically associate with food poisoning: cramps, vomiting, explosive diarrhea, and in severe cases, dehydration.

And the worst part about staph is that you can't tell if your food has been infected; there's no signs of spoilage such as a bad smell or funny color change. Reheating it in a microwave won't kill off this bacteria, either, so letting it sit out and then popping it in the microwave puts you at more of a risk of ingesting these enterotoxins.

If ignoring food safety is just a habit your friend has in general, then he is more likely to get a foodborne illness from leaving raw meat unrefrigerated for too long, whether that's in the car after the grocery store or on the counter to thaw. And sometimes even refrigerating foods won't work; listeria, which is potentially dangerous and marked by fever, stiff neck, weakness, and vomiting, can survive even in the fridge. It's found in deli meats and hot dogs, unpasteurized milk, soft cheeses, and meat pâtés.

What Will Probably Happen: If it's pizza, probably nothing. The acidity in the pizza sauce helps keep the spread of bacteria relatively down, Tierno explains. As long as you reheat it to over 165 degrees Fahrenheit the next day in an oven or on a frying pan—microwaves tend to miss spots in food and don't effectively kill bacteria—you can eat it with little worry, he says. It's not ideal, but it probably won't get you majorly sick.

If it's another type of food, especially something with cooked meat or deli meat, it sort of depends. Staph can grow on any perishable food, most commonly meat, poultry, eggs, mayo-based salads, eggs, and dairy products. Other factors such as temperature of the room, who has handled the ingredients, and moisture of the food can play a role in how quickly the bacteria multiplies, so it's hard to determine which foods will end up getting infected.

The CDC reports that 48 million Americans, about 1 in 6, get sick from a foodborne illness each year. Being careless with food safety is more or less playing Russian roulette with your immune system and your bowel movements. And is that a risk your friend is really willing to make?

What You Should Tell Your Friend: In general, don't make a habit of leaving food out on the counter overnight. Stick to the two-hour rule: Perishable foods can be left out at room temperature for two hours, then they must be refrigerated. Hot foods should stay hot, above 140 degrees Fahrenheit, and cold foods cold, below 40 degrees. And if he's accidentally left raw meat unrefrigerated for more than a couple hours or has deli meat in his fridge that's older than four days, it's better to be safe than sorry and throw it out.

If for some reason your friend went crazy and ordered a bunch of pizzas, he should be sure to eat the leftovers within a couple days or throw them in the freezer. Magoulas says leftovers can only last in the fridge three to four days, then they should be tossed. Read This Next: Chill, Your Moscow Mule Probably Isn't Going to Poison You