Wondering whether mayonnaise can safely sit on the counter? Learn how long mayo can stay unrefrigerated, when it should be thrown away, and how to store it safely.
Many people grew up seeing mayonnaise sitting on the kitchen counter, especially in homes where it was used frequently. But when it comes to food safety, how long mayonnaise remains unrefrigerated matters.
How Long Can Mayonnaise Stay Out?
Once opened, commercially prepared mayonnaise should generally not be left at room temperature for more than 2 hours. If the temperature is above 90°F (32°C), the safer limit is about 1 hour.
This is because bacteria can multiply rapidly in foods kept in the temperature danger zone, roughly 40°F–140°F (4°C–60°C).
What If It Has Been Sitting Out for Several Days?
If an opened jar of mayonnaise has been sitting on the counter for a few days, it is safest to throw it away, even if:
- It smells normal
- It looks perfectly fine
- The texture hasn’t changed
- Your nana or family has always stored it that way
Unfortunately, you cannot reliably determine whether harmful bacteria are present simply by looking at or smelling food.
What About Unopened Mayonnaise?
An unopened, commercially produced jar is generally shelf-stable and can be stored in a cool, dry pantry until its best-by date, provided the packaging hasn’t been damaged.
After opening, however, refrigeration is the safest choice.
Why Does Refrigeration Matter?
Refrigeration slows the growth of bacteria and helps maintain the quality of mayonnaise. Keeping the jar cold also helps preserve its flavor and texture for longer.
For the best results:
- Refrigerate mayonnaise after opening.
- Keep the jar tightly closed.
- Use a clean spoon or knife every time.
- Avoid leaving the jar sitting beside a hot stove or in direct sunlight.
- Follow the storage instructions printed on the specific product.
What About Homemade Mayonnaise?
Homemade mayonnaise deserves extra caution because it may contain raw or lightly cooked eggs. It generally has a much shorter safe storage period than commercially manufactured mayonnaise.
If homemade mayo has been left at room temperature for an extended period, it’s better to discard it rather than take a chance.
The Simple Rule to Remember
Opened mayonnaise + several days on the counter = don’t eat it.
It may be disappointing to throw away a jar that looks perfectly normal, but foodborne bacteria aren’t always visible or detectable by smell.
And if you’re pregnant, elderly, immunocompromised, or serving mayonnaise to a young child, being particularly careful with foods that have been improperly stored is especially important.