Food expiration dates are confusing — and not just because they don’t necessarily indicate when you should throw food out. “Sell by” and  “best by” refer to peak quality, not safety. And to add to the confusion, the terms aren’t federally regulated or required (except in the case of baby formula and certain baby foods). Most foods are fine after the dates on their packaging pass, though they may be slightly subpar. 

There are a handful of foods, however, where timing actually does matter. In these cases, it’s less about flavor and more about whether that meal is going to haunt you tomorrow. The common thread is bacteria: Moist, low-acid, ready-to-eat foods make especially good hosts, and the pathogens that can make you sick (like listeria and salmonella) don’t always announce themselves with a smell. Here are the foods you should toss once the expiration date has passed (or sooner if you’ve opened them).

Deli Meat and Cold Cuts 

Lunch meats are prime territory for listeria, a bacterium capable of growing at temperatures as low as 31 degrees Fahrenheit — meaning “well, it stayed cold” isn’t the protection it seems to be. And, as the FDA notes, the longer a ready-to-eat refrigerated food sits, the more opportunity listeria has to grow. 

While it’s rare for healthy people to get extremely ill from listeria infection, it can be fatal for newborns and those who are immunocompromised, and it can cause miscarriages in pregnant people. So you shouldn’t let freshly sliced deli meat linger too long in your fridge: It has only three to five safe days before you should toss it out. The prepackaged versions you get in the refrigerated aisle last a little longer if they’re unopened — usually about two weeks — but once the seal is broken, you’re back to the same short window.

Soft Cheeses 

Solid blocks of hard cheeses (cheddar, Parmesan, and pecorino, for example) are very forgiving. They last for up to four weeks in your fridge, and even if they get a little moldy, they’re not a lost cause — just cut an inch around the moldy spot and carry on. (If your hard cheese is grated or shredded and exhibits signs of mold, though, you should throw it out.)  

When it comes to soft, high-moisture cheeses like ricotta, cream cheese, goat cheese, or brie, it’s best to follow package guidelines. And definitely toss them at any sign of mold: In soft cheese, it spreads throughout and can’t be cut out. Soft cheeses are also more prone to listeria. The Academy of Nutrition and Dietetics suggests using cream cheese within two weeks of opening, and ricotta within one. Bottom line: Toss at the first sign of spoilage or by the date on the package — whichever comes first.

Raw Fish and Shellfish 

Seafood is one of the most perishable things in your kitchen. Eating improperly stored fish can cause various types of food poisoning, resulting in an upset stomach, diarrhea, or worse. For this reason, the USDA recommends cooking or freezing raw fish within 48 hours of purchase. Certain types of shellfish give you a little more leeway: Clams, mussels, and oysters need to be eaten within three days if you buy them live or in five to 10 days if they’ve been commercially shucked and jarred. Scallops should be consumed within one to three days. Any sour, fishy, or ammonia-like smell is your cue to throw seafood out immediately. And while we don’t want to scare you, here’s one additional thing to consider: There are some types of food poisoning you can get from fish that no amount of cooking can prevent. If you feel sick after eating seafood, seek medical advice.

Ground Meat 

Think about this: A steak carries bacteria mostly on its surface, which is why searing the outside does a lot of work in making it both safe and tasty. However, it’s smart to consider whether your meat has been mechanically tenderized. The process, which involves poking the meat with sharp needles to break up the muscle, can transfer bacteria into the center of the steak. Similarly, grinding meat mixes that bacteria all the way through, so ground beef, turkey, and pork spoil faster and carry more risk. The USDA says to use or freeze ground meat within two days of purchase. 

Bagged Salads and Leafy Greens 

Leafy greens can carry bacteria that may become a problem once the leaves break down and get soggy, allowing the bacteria to proliferate. So, once greens go slimy or brown, they’re done (and wilted salad, being what it is, means you probably wouldn’t want to use them anyway). This applies even to prewashed mixes. According to FoodSafety.gov, bagged produce, if unopened, “will last [three to five] days after date on bag; after opening it will last [two] days.”

Sprouts 

Bean sprouts can elevate a sandwich with crunch and freshness in a way few other veggies can, but beware: These tiny shoots are grown in exactly the warm, humid conditions bacteria love. Salmonella, listeria, and E. coli can all be found on raw sprouts. The FDA notes that if even a few harmful bacteria are present on the seed, they can multiply to high levels during sprouting.  The safe window is short — roughly five to 10 days after purchase — and if you’re pregnant or immunocompromised, the FDA advises skipping raw sprouts altogether.

Mayonnaise and Creamy Dressings 

Mayo, aioli, and many creamy dressings are egg- and dairy-based and high in moisture, which makes them hospitable to bacteria once the seal is broken and a knife is going in and out of the jar. The USDA gives open commercial mayonnaise about two months in the fridge; creamy dressings have three to four weeks in the fridge. Even if the date hasn’t yet approached, if it smells off or looks weird, throw it out. 

Prepared Deli Salads 

Potato, egg, tuna, and pasta salads combine a few risk factors at once: They’re moist, often mayo-based, and scooped with a spoon, which can introduce bacteria. That exposure adds up fast, especially if the container is taken out of a cold fridge and drifts into the danger zone that allows bacteria to thrive (between 40 degrees Fahrenheit and 140 degrees Fahrenheit). Deli salads like coleslaw, potato salad, and tuna salad are among the ready-to-eat foods that can carry listeria, which will thrive even if you put the dish back in the fridge. The USDA gives store-bought and homemade deli salads about three to five days — and unlike a wilted salad, a contaminated one won’t necessarily look or smell wrong, so play it safe and toss it when that timer is up (or sooner if it’s been allowed to linger at room temperature).

Cold-Pressed Juice 

The reason raw green juices cost what they do is also why they don’t last: They skip the pasteurization that kills bacteria, which leaves them prone to contamination and with a short life of three to five days once opened. Untreated juices are required to carry a warning label, and the FDA advises that children, older adults, pregnant people, and anyone immunocompromised should avoid them.

The Takeaway 

The catch with all of these is that the sniff test gets you only so far. A funky smell is a good reason to toss something, but it’s important to also remember that the absence of funk isn’t a good reason to eat it — listeria and salmonella can be present with no smell at all. 

For most of your pantry (especially dry goods), the dates on the packaging are a loose suggestion and your nose is a fine backup. For this short list, however, the date and the open-container clock are both worth taking at their word — and when you’re genuinely unsure, the few dollars you’d lose chucking the item are rarely worth the discomfort you’d suffer if it is indeed spoiled.

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It happens to all of us: You’re chopping veggies for a salad or shoveling popcorn into your mouth while watching a movie, and a morsel of food ends up on the floor. Thoughts pass fleetingly through your mind: If you pick it up quickly, is it still OK to eat? Is the five-second rule a real thing? The answers to these questions may be more complicated than they seem.

Background on Bacteria

No matter how well you wash your hands or scrub your sink, you spread bacteria among any surfaces you touch. A 2012 study found that human skin was the main source of bacterial transfer across kitchen surfaces, and that infrequently cleaned areas like exhaust fans, refrigerator door seals, and floors had the highest diversity of bacteria. 

At the same time, anything that touches a surface in your kitchen — including food — picks up bacteria. A Dorito doesn’t have to fall on the floor to acquire a few microbes; it could simply come into contact with the kitchen counter, which actually harbors more coliform bacteria per square inch than the floor, according to a 1998 study. Cutting boards, dish towels, and sponges can also bear bacteria and spread them among the surfaces they touch.

The important thing to remember is that most bacteria found in kitchens and food-prep areas are not harmful to your health. However, pathogens such as salmonella and E. coli, which are often brought into kitchens via contaminated meat or produce, can linger on improperly cleaned surfaces. If you drop a piece of food and it falls directly on disease-causing bacteria on the floor, you could, theoretically, get sick from eating that food — but chances of that happening are low, Paul Dawson, a food scientist at Clemson University, told Prevention.

Five-Second Rule Fiction?

The apocryphal five-second rule suggests that food that’s dropped on the floor is safe to eat if it’s retrieved within five seconds, ostensibly because it doesn’t have time to acquire pathogens. Dawson led a frequently cited 2007 study that assessed whether the rule was scientifically sound by dropping sliced bread and bologna on tile, wood, and carpeted floors contaminated with salmonella and measuring the bacterial loads the foods picked up after various amounts of time. 

Though the carpet-to-bologna pathway transferred less than 1% of bacteria, “over 99% of bacterial cells were transferred from the tile to the bologna” after five seconds. Overall, 48% to 70% of bacteria moved from wood or tile floors to the bread and bologna within seconds, disproving the basic idea that brevity of time prevents bacterial migration from floor to food.

Later studies have shown that the moisture content of the food, the floor material, and duration affect bacterial transfer. In general terms, the stickier or wetter the food is, and the longer it spends on the floor, the more bacteria it’s going to acquire, though carpet tends to transfer fewer bacteria than harder surfaces. 

The Bottom Line 

Food that’s been dropped on the floor is unlikely to make you sick. But if you decide to eat it, give it a thorough rinse. Anything you can’t wash should be thrown out.

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