I still remember walking into my nana’s kitchen and spotting an open jar of mayonnaise sitting on the counter. She smiled and said, “It’s fine—I use it every day.” Meanwhile, I couldn’t stop wondering if it should have been back in the refrigerator hours ago.
If you’ve ever had the same concern, you’re not alone. Mayonnaise often causes confusion because some people think it’s highly perishable, while others leave it out without a second thought.
So, how long can mayonnaise safely stay out? The answer depends on whether the jar is unopened, opened, or mixed into foods like potato salad or egg salad.
Does Mayonnaise Need to Be Refrigerated?
An unopened jar of commercially made mayonnaise can usually be stored in a cool, dry pantry until the expiration date.
Once the jar is opened, however, manufacturers recommend refrigerating it after each use. Chilling the mayonnaise helps maintain its quality and slows the growth of harmful bacteria that can be introduced after opening.
How Long Can Opened Mayonnaise Sit Out?
An opened jar of mayonnaise shouldn’t stay at room temperature for more than 2 hours.
If the room temperature is above 90°F (32°C), such as during a summer picnic or outdoor barbecue, the safe limit drops to 1 hour.
After that, it’s safest to discard the mayonnaise.
Why Is Commercial Mayonnaise Different?
Many people are surprised to learn that store-bought mayonnaise is fairly acidic.
The vinegar or lemon juice in commercial mayonnaise helps reduce bacterial growth. That’s one reason unopened mayonnaise is shelf-stable.
The bigger concern isn’t the mayonnaise itself—it’s what happens after the jar has been opened. Every time a knife or spoon goes into the jar, bacteria can be introduced, making refrigeration important.
What About Homemade Mayonnaise?
Homemade mayonnaise is a different story.
Because it’s often made with raw egg yolks and doesn’t contain the same preservatives as commercial products, homemade mayonnaise should always be refrigerated and used within a few days.
Never leave homemade mayonnaise sitting on the counter for extended periods.
Mayonnaise in Salads Doesn’t Last as Long
Foods made with mayonnaise require extra care.
This includes:
- Egg salad
- Potato salad
- Chicken salad
- Tuna salad
- Pasta salad
- Coleslaw
These dishes contain other perishable ingredients that can spoil quickly if left at room temperature.
Like opened mayonnaise, they should not remain unrefrigerated for more than 2 hours, or 1 hour in hot weather.
How to Tell If Mayonnaise Has Gone Bad
Sometimes spoiled mayonnaise gives obvious warning signs.
Throw it away if you notice:
- A sour or unpleasant smell
- Mold
- Unusual discoloration
- Separation that doesn’t mix back together
- An off taste
If you’re unsure how long it’s been sitting out, it’s usually safer to replace it.
Tips for Storing Mayonnaise Safely
Keeping mayonnaise fresh is simple.
Follow these storage tips:
- Refrigerate after opening.
- Always use a clean spoon or knife.
- Close the lid tightly after each use.
- Store it in the main refrigerator compartment rather than the door if possible.
- Check the expiration date before using it.
These habits help maintain both quality and food safety.
Frequently Asked Questions
Can unopened mayonnaise stay in the pantry?
Yes. Commercial unopened mayonnaise is generally safe to store in a cool, dry pantry until its expiration date.
Is mayonnaise the reason potato salad spoils?
Not usually. Foods like cooked potatoes, eggs, and chicken are often the ingredients that become unsafe when left at room temperature.
Can you eat mayonnaise that sat out overnight?
No. If opened mayonnaise has been left out overnight, it’s safest to throw it away.
How long does opened mayonnaise last in the refrigerator?
Once opened, commercial mayonnaise generally stays at its best for about 2 months when refrigerated, though always follow the manufacturer’s date and storage instructions.
Final Thoughts
An open jar of mayonnaise may seem harmless sitting on the counter, but food safety experts recommend refrigerating it after every use.
While commercial mayonnaise is more stable than many people realize, leaving it out for too long increases the risk of bacterial growth after the jar has been opened.
When in doubt, remember the 2-hour rule. A quick trip back to the refrigerator can help keep your sandwiches, salads, and family meals both fresh and safe.
