Don’t forget your fridge in your annual spring cleaning frenzy. And not just the appliance—clean out the food in it, to make sure it’s not growing bacteria that could be harmful to your family’s health.

Many condiments like mayonnaise, mustard, ketchup, and salad dressing stay fresh for six months or more—if they’re unopened. Check each package for expiration dates. Once they’re opened, however, they should be tossed after three months. If your condiments have been open for three months, or you’re not sure how long ago they were opened, toss them.

For unopened dairy products like yogurt and sour cream, rely on the expiration dates printed on the container. Again, once they’re opened, this changes and they should be discarded within two weeks of opening, regardless of the printed date.

Butter is good for three months stored in the refrigerator—and your freezer for up to a year. So if you’ve bought more butter than you’ve been able to use, stick it in the freezer before the expiration date on the package.

Lastly, what about leftovers that lurk in everyone’s fridge? Typically leftovers stored in airtight containers will keep for four to five days. If anything looks or smells bad, however, it’s always best to throw it away. And if you don’t know how long it’s been in there, err on the side of caution and discard it—if you even dare to open the lid.