You open the refrigerator, reach for the mayonnaise, and suddenly stop.
How long has this jar been sitting here?
Maybe you remember buying it weeks ago. Maybe it has been there for months. The label still looks fine, the mayonnaise looks normal, and there is no obvious sign that anything is wrong.
So… is it still safe to eat?
Mayonnaise is one of those foods that can create confusion because its shelf life depends on several factors: whether it is commercially made or homemade, whether it has been opened, how cold your refrigerator is, how it has been handled, and what the package instructions say.
The good news is that you don't have to guess.
Here is what you should know before spreading that old mayonnaise on your sandwich.
The Simple Answer: How Long Does Mayo Last?
For commercially prepared mayonnaise, the safest approach is to follow the storage instructions and use-by guidance printed on the container.
Once opened, mayonnaise should generally be kept refrigerated. Many food-safety and storage guides use about two months as a quality guideline for opened commercial mayonnaise, but that should not be treated as a universal guarantee that every jar is safe for exactly that long.
The condition of the product and how it has been stored matter.
If mayonnaise has repeatedly been left warm, contaminated with dirty utensils, or stored improperly, it can become unsafe sooner.
Homemade mayonnaise is different. Because homemade versions may contain raw eggs and usually do not have the same commercial processing and acidity controls, they have a much shorter storage life. A conservative guideline is to use homemade mayonnaise within about 3–5 days when properly refrigerated, with extra caution if raw eggs are involved.
When in doubt, throwing it away is safer than taking a chance.
Unopened Mayonnaise: Does It Need to Be Refrigerated?
An unopened commercial jar of mayonnaise is usually more stable than an opened jar.
Before opening, store it according to the manufacturer's instructions. If the label says to keep it in a cool, dry place until opened, there is generally no need to move it into the refrigerator immediately.
However, avoid storing it somewhere exposed to excessive heat, sunlight, or large temperature changes.
A kitchen cabinet away from the stove is usually a better location than a warm countertop.
Once you open the jar, refrigeration becomes important.
Why Does Mayonnaise Last Longer Than You Might Expect?
Mayonnaise contains ingredients such as vinegar or lemon juice, which contribute acidity to the product. Commercial mayonnaise is also manufactured under controlled conditions and commonly uses pasteurized egg ingredients.
That combination helps commercial mayonnaise remain relatively stable compared with many other egg-based foods.
But stable does not mean impossible to spoil.
Once a jar is opened, it can be exposed to air, food particles, dirty utensils, and temperature changes. Every time you dip a knife or spoon into the jar, you create another opportunity for contamination.
That's why proper storage and handling matter just as much as the date printed on the package.
What About the “Best By” Date?
This is one of the most misunderstood parts of food labeling.
A “best by” date generally relates to quality, not necessarily an exact moment when the food suddenly becomes unsafe.
After that date, a properly stored unopened product may still have acceptable quality. But the date alone doesn't tell you everything.
For opened mayonnaise, you also need to consider:
When you opened it
Whether it has stayed refrigerated
Whether the refrigerator remains at a safe temperature
Whether clean utensils were used
Whether the container was contaminated
Whether the jar or lid has been damaged
Whether the product shows signs of spoilage
So don't rely on the printed date alone.
How Can You Tell If Mayonnaise Has Gone Bad?
Sometimes spoiled mayonnaise gives you obvious warning signs.
1. Mold
If you see mold anywhere in the mayonnaise, throw the entire jar away.
Don't simply scrape off the visible mold and use the rest.
Mold can spread beyond the area you can see, and mayonnaise is not worth taking that risk.
2. Strange or Unpleasant Odor
Fresh mayonnaise has a recognizable creamy, tangy smell.
If your mayonnaise develops an unusually sour, rotten, rancid, or otherwise unpleasant odor, discard it.
However, remember that smell is not a perfect safety test. Some harmful microorganisms may not produce an obvious smell.
3. Unusual Color
If mayonnaise becomes noticeably yellow, brown, gray, pink, green, or otherwise different from its normal appearance, it is best to throw it away.
A small amount of natural separation isn't automatically proof of spoilage, but significant changes in appearance combined with other warning signs should not be ignored.
4. Unusual Texture
If the mayonnaise becomes extremely watery, lumpy, curdled-looking, or otherwise dramatically different from its normal consistency, don't assume it is safe.
Texture changes can happen for different reasons, but when you aren't sure what caused them, discarding the product is the safer option.
5. A Damaged or Bulging Container
A leaking, swollen, badly damaged, or otherwise abnormal container is another reason not to use the product.
When the packaging itself looks suspicious, don't take chances.
Don't Use the Taste Test
One common mistake is taking a tiny bite of questionable mayonnaise to decide whether it is still good.
Don't do this.
You cannot reliably determine whether food is safe simply by tasting it. Dangerous microorganisms can sometimes be present without noticeably changing the food's smell, taste, or appearance.
If you are genuinely unsure about mayonnaise that has been stored improperly or for an unknown amount of time, the safest choice is to throw it away.
A new jar costs far less than dealing with foodborne illness.
How Cold Should Your Refrigerator Be?
Your refrigerator should be kept at 40°F (4°C) or below.
A refrigerator that is too warm can shorten the safe storage life of perishable foods.
It's also worth remembering that refrigerator temperatures aren't always perfectly consistent. The door is frequently opened and closed, causing temperature fluctuations.
For that reason, especially temperature-sensitive foods are often better stored toward the back of the refrigerator rather than in the door.
What Happens If Mayo Is Left Out?
This is where many people get confused.
Commercial mayonnaise itself is more acidic and stable than many foods, but once mayonnaise is incorporated into foods such as chicken salad, egg salad, tuna salad, or sandwiches, the overall dish can become more perishable.
As a general food-safety rule, perishable foods should not be left at room temperature for more than 2 hours.
If the surrounding temperature is above 90°F (32°C), the limit is generally 1 hour.
This becomes particularly important at:
Outdoor picnics
Barbecues
Beach gatherings
Hot cars
Outdoor parties
Buffets
Warm kitchens
If a mayo-containing dish has been sitting out for too long, don't try to rescue it by putting it back in the refrigerator.
Homemade Mayonnaise Is a Different Story
Homemade mayonnaise deserves extra caution.
Many homemade recipes use raw eggs, which can carry Salmonella. Commercial mayonnaise is typically produced under controlled conditions and commonly uses pasteurized egg ingredients, while homemade preparation may not provide the same safeguards.
If you make mayonnaise at home, consider using pasteurized eggs or pasteurized egg products, especially for people who are more vulnerable to foodborne illness.
Homemade mayonnaise should be refrigerated promptly and used within a short period. A conservative storage window is around 3–5 days, depending on the recipe, ingredients, acidity, egg handling, and refrigeration.
If you don't know exactly how it was prepared or how long it has been stored, it's safer not to eat it.
Can You Freeze Mayonnaise?
Technically, mayonnaise can be frozen, but freezing generally isn't recommended.
The problem isn't necessarily that freezing makes the mayonnaise poisonous. Instead, freezing can seriously affect its texture.
Mayonnaise is an emulsion, meaning ingredients such as oil and water are held together in a stable mixture. Freezing can disrupt that structure.
After thawing, you may notice:
Separation
Watery liquid
A grainy texture
Oil separating from the other ingredients
A less creamy consistency
Even if you manage to mix it back together, the original quality may not return.
For most people, refrigeration is a much better option.
What About Mayonnaise in Potato Salad or Sandwiches?
This is another important distinction.
A jar of commercial mayonnaise isn't the same thing as a prepared potato salad sitting outside at a summer picnic.
Once mayonnaise is mixed with ingredients such as potatoes, eggs, chicken, tuna, or vegetables, the entire dish needs to be treated as a perishable food.
The safest approach is to keep these foods cold and return them to the refrigerator promptly.
If you're serving them outdoors, use an insulated cooler with plenty of ice or cold packs.
Don't rely on the mayonnaise alone to protect the entire dish.
Common Mistakes That Can Shorten Mayo's Shelf Life
Even a perfectly good jar can become contaminated through poor handling.
Here are some common mistakes to avoid.
Using a Dirty Knife or Spoon
Never scoop mayonnaise with a utensil that has already touched another food.
For example, using a knife to spread mayonnaise on bread and then putting that same knife back into the jar can introduce crumbs and other microorganisms.
Use a clean utensil instead.
Leaving the Lid Open
After using mayonnaise, close the container tightly and return it to the refrigerator.
Don't leave the jar sitting uncovered on the counter.
Storing It in a Warm Refrigerator Door
The refrigerator door experiences more temperature fluctuations than the interior shelves.
For better temperature stability, store mayonnaise in a colder, consistent part of the refrigerator while following the product's storage instructions.
Ignoring the History of the Food
Sometimes the biggest problem isn't what the mayonnaise looks like today.
It's what happened to it yesterday.
If the jar was accidentally left in a hot car for hours, taken to a picnic and left outside, or repeatedly warmed and chilled, appearance alone can't tell you whether it remains safe.
A Quick “Keep It or Toss It?” Checklist
Before using an older jar of mayonnaise, ask yourself:
Is it commercially made?
Commercial mayonnaise generally has more controlled processing than homemade mayonnaise.
Has it been continuously refrigerated after opening?
If not, be cautious.
Does the container look normal?
Avoid damaged, leaking, or bulging containers.
Is there mold?
If yes, throw it away.
Does it have an unusual smell, color, or texture?
If yes, discard it.
Do you know how long it has been open?
If you don't, don't assume it's safe.
Was it exposed to heat for an extended period?
If yes, don't rely on the appearance alone.
Are you unsure?
When in doubt, throw it out.
So, How Long Does Mayo Really Last?
There isn't one number that applies perfectly to every jar.
For commercial mayonnaise, the manufacturer's instructions should be your first reference. Once opened, keeping it refrigerated and using it within the product's recommended period is the safest approach. Around two months is often used as a quality guideline for opened commercial mayonnaise, but it isn't a universal safety guarantee.
For homemade mayonnaise, the storage period is much shorter. Because recipes and egg handling vary, a cautious guideline is approximately 3–5 days in the refrigerator, especially when raw eggs are used.
And remember: time, temperature, handling, and contamination all matter.
The refrigerator can slow microbial growth, but it doesn't stop it completely.
The Bottom Line
That forgotten jar of mayonnaise doesn't have to be a mystery.
Keep unopened commercial mayonnaise according to the label. Once opened, refrigerate it promptly and handle it with clean utensils. Keep your refrigerator at or below 40°F (4°C), and be especially careful with mayonnaise-based salads and other prepared foods.
Don't assume that a “best by” date automatically means the food is unsafe, but don't assume that food is safe simply because the date hasn't passed either.
And most importantly, never use taste as your safety test.
If the mayonnaise has visible mold, an unusual appearance, an unpleasant odor, damaged packaging, or a history of improper storage, it's not worth the risk.
Sometimes the smartest thing you can do with an old jar in the back of the refrigerator is simply throw it away.
Because when it comes to food safety, saving a few dollars on mayonnaise isn't worth gambling with your health.
Have you ever found a forgotten jar of mayonnaise in the back of your refrigerator?
Did you keep it—or throw it away?
Share this article with someone who always checks the expiration date but still isn't sure whether their mayo is safe to eat.
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