Even if food is stored properly, experts caution against eating certain items after their expiration date. While “sell by” dates posted on supermarket products often indicate peak freshness — and some foods can still be safe shortly after those dates — expiration or “use by” dates are different. Once a product passes that point, it may harbor dangerous bacteria that can cause illness.

According to Real Simple, consuming certain foods after their expiration date can increase the risk of exposure to harmful pathogens. Here are some of the biggest offenders to watch out for:

• Deli meats. Processed meats such as ham, turkey, and roast beef are highly perishable and can quickly develop harmful bacteria like Listeria after their expiration date. These should always be eaten by the “use by” date.

• Raw meat. Dr. Cynthia Odogwu warns that raw meats—including chicken, beef, and pork—are likely to spoil after their expiration date and can grow dangerous bacteria such as salmonella and E. coli, both of which can cause serious foodborne illness.

• Dairy products. Milk, soft cheeses, and yogurt can spoil quickly and harbor harmful bacteria, including Salmonella and E. coli, especially when past their expiration date. Unpasteurized cheeses, such as some versions of Brie and Camembert, should be discarded once they expire because they can become contaminated with Listeria.

• Baby formula. “This is the most important one on the list,” says Don Schaffner, a food microbiologist and distinguished professor at Rutgers University School of Environmental and Biological Sciences. “It’s the sole source of nutrition for babies being fed formula. We know it contains the listed nutrients until the date on the label. But feeding your baby this after that date could be contributing to a nutrient deficiency.” According to Prevention, baby formula should always be thrown out after the “use by” date.

• Eggs. While eggs can sometimes last a little past their sell-by date if properly refrigerated, it’s safest to consume them by the expiration date to avoid the risk of Salmonella.

• Fresh seafood. Fish and shellfish spoil very quickly and can cause serious foodborne illnesses if eaten after their expiration date. It’s best to enjoy seafood the day it’s purchased.

• Prepared salads. Store-bought salads made with mayonnaise or dairy (such as potato or chicken salad) should be consumed by their expiration date to avoid bacterial contamination. “Throw out pre-package, ready-to-eat salads once they expire,” advises Odogwu.

• Mushrooms. Spoiled mushrooms can harbor botulism or other dangerous toxins. If they appear slimy or discolored, they should be discarded immediately. To help mushrooms stay fresh longer, store them in a paper bag lined with a paper towel in the refrigerator to prevent excess moisture buildup.