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Mayonnaise is one of those refrigerator staples that can sit quietly on the door for weeks—or even months—until you suddenly wonder whether it is still safe to eat.
The good news is that commercial mayonnaise is more stable than many people realize. Because it is made with acidic ingredients such as vinegar or lemon juice, mayonnaise itself generally does not support bacterial growth as easily as many other foods. However, proper storage still matters, and homemade mayonnaise has a much shorter storage window. (Ask USDA)
How Long Does Opened Mayo Last?
According to the USDA’s food-storage guidance, commercial mayonnaise that has been opened and refrigerated should generally be used within about two months. This recommendation assumes the refrigerator is maintained at 40°F (4°C) or below. (FSIS)
That does not necessarily mean a jar becomes dangerous the moment two months have passed. Food-storage timeframes are useful guidelines for maintaining quality and safety, and manufacturers may provide specific instructions that should also be followed.
If the jar has been sitting in the refrigerator for longer than recommended, check the label and consider how it has been handled before deciding whether to keep it.
What About Unopened Mayonnaise?
Unopened commercial mayonnaise is designed to be shelf-stable before opening when the package indicates that refrigeration is not required.
USDA guidance lists commercial mayonnaise as a shelf-stable product before opening, while recommending refrigeration after opening. Always follow the storage instructions printed on your particular jar, especially if the product specifically says to keep refrigerated. (FSIS)
Once opened, keeping mayonnaise consistently cold helps preserve its quality.
Why Does Mayonnaise Get Blamed for Food Poisoning?
Mayonnaise often gets blamed when someone becomes sick after eating foods such as potato salad, chicken salad, tuna salad, or sandwiches.
However, the mayonnaise itself is not necessarily the culprit. The USDA explains that the acidity of mayonnaise tends to inhibit bacterial growth. Other ingredients—such as meat, poultry, fish, eggs, or cooked vegetables—can be more vulnerable when a prepared dish is left at unsafe temperatures. (Ask USDA)
This distinction is important because mayonnaise-based dishes can still become unsafe if they are left unrefrigerated for too long.
Follow the Two-Hour Rule
Temperature is one of the most important factors in food safety.
The USDA recommends keeping your refrigerator at 40°F or below. Bacteria can multiply rapidly between 40°F and 140°F, commonly called the “danger zone.” (FSIS)
For foods that require refrigeration, the FDA recommends following the two-hour rule: refrigerate them promptly rather than leaving them at room temperature for extended periods. In hot conditions, the safe window can be even shorter. (U.S. Food and Drug Administration)
So if mayonnaise or a mayonnaise-based dish has been sitting on a kitchen counter for several hours, simply returning it to the refrigerator does not necessarily make it safe.
How Can You Tell If Mayo Has Spoiled?
Appearance and smell can provide useful warning signs, although you should never rely on them alone to determine whether food is safe.
Discard mayonnaise if you notice obvious mold, an unusual color, a distinctly unpleasant odor, or other signs that the product has deteriorated.
Also pay attention to the condition of the container. A damaged, leaking, or swollen package should not be treated as normal.
Remember that harmful bacteria do not always produce an obvious change in smell, taste, or appearance. USDA guidance specifically warns that pathogens may be present without making food look or smell spoiled. (FSIS)
Homemade Mayo Is Different
Homemade mayonnaise requires considerably more caution.
Traditional homemade mayonnaise can contain raw eggs, which may carry Salmonella. The USDA recommends using pasteurized eggs or pasteurized egg products when making mayonnaise that will not be cooked. Once prepared, homemade mayonnaise made with pasteurized eggs should be refrigerated and used within four days. (Ask USDA)
That is dramatically shorter than the recommended refrigerator window for commercial mayonnaise.
Should You Freeze Mayonnaise?
Freezing mayonnaise is generally not recommended. USDA guidance notes that mayonnaise does not freeze well because freezing can damage its emulsion, causing it to separate and develop an unpleasant texture after thawing. (FSIS)
For most households, refrigeration is the better option.
The Bottom Line
For commercial mayonnaise, about two months in the refrigerator after opening is the USDA guideline to keep in mind. Store it at 40°F or below, follow the manufacturer’s instructions, and avoid leaving mayonnaise-based foods at room temperature for extended periods. (FSIS)
And if you are dealing with homemade mayonnaise, remember that its storage life is much shorter—generally about four days when made with pasteurized eggs and kept refrigerated.
When in doubt about a questionable jar or food that has been stored improperly, the safest choice is to throw it away.