How Long Opened Mayonnaise Lasts in the Refrigerator

Opened mayonnaise stays safe to eat for about two to three months when stored in the refrigerator at 40°F or below

Once you open a jar of mayonnaise, the clock starts. The two to three month window is the standard recommendation from the USDA and most mayonnaise manufacturers, though some brands print their own timeline on the label—check yours first. This timeline assumes your refrigerator stays at a consistent 40°F or colder and you use a clean spoon every time you scoop.

The reason mayonnaise lasts this long is its acidity. Commercial mayonnaise contains vinegar or lemon juice, which creates an environment where harmful bacteria struggle to grow. That protective acid is why homemade mayo—which often skips the vinegar or uses less—spoils much faster, usually within a week. If you make mayo at home, treat it as a perishable item and use it quickly.

The jar's seal matters less once it's open. What matters is how you handle it after that first use: keep the lid on between servings, store it in the coldest part of your refrigerator (usually the back of a shelf, not the door), and never double-dip or leave it sitting on the counter while you make a sandwich.

Key Takeaways

• Commercial mayonnaise lasts two to three months after opening if kept at 40°F or below, but always check your jar's label for the manufacturer's recommendation.
• Homemade mayonnaise spoils much faster—within one week—because it lacks the preservative acidity of commercial versions.
• Store opened mayo in the coldest part of your refrigerator, not on the door where temperature fluctuates, and always use a clean utensil to scoop.
• Signs of spoilage include an off smell, mold, separation of oil from the base, or a sour taste that goes beyond the normal tang.

Why the Door Is the Wrong Place

Your refrigerator door is the warmest part of the fridge. Every time someone opens it, warm air rushes in, and the temperature inside the door compartment can swing 10 to 15 degrees. Mayonnaise is sensitive to temperature swings because they speed up the breakdown of its emulsion—the delicate balance of oil, egg, and acid that holds it together.

Store opened mayo on a middle or back shelf instead, where the temperature stays steady. If your refrigerator has a dedicated condiment shelf, that's often a good spot. The goal is to minimize how many times the jar experiences a temperature change.

How to Tell When Mayonnaise Has Gone Bad

Smell is your first alert. Fresh mayo has a tangy, slightly eggy scent. If it smells sour in a way that feels off—sharper or more vinegary than usual—or if it has any musty or rotten note, don't use it. Trust your nose; it's more reliable than a calendar.

Look for visible mold, which can appear as dark spots or a fuzzy layer on the surface or sides of the jar. Even a tiny spot means the whole jar should go. Oil separation is normal—mayo can look slightly oily on top after sitting—but if the oil has turned cloudy or the base looks watery and won't mix back together, the emulsion has broken down and it's time to replace it.

Taste is a last resort. If you're unsure after smelling and looking, dip a clean spoon in and taste a tiny amount. Spoiled mayo tastes noticeably sour or off in a way that's different from its normal tang. If anything feels wrong, throw it out. The cost of a new jar is far less than the cost of food poisoning.

Storage Containers and Cross-Contamination

Keep mayo in its original jar whenever possible. The jar is designed to protect it, and the label tells you the expiration date and storage instructions. If you transfer it to another container, you lose that reference and introduce the risk of contamination from whatever was in that container before.

When you scoop mayo, use a clean spoon or knife every single time. Bacteria from bread, lettuce, or whatever else you're spreading it on can transfer into the jar and shorten its life. If you share a jar with other people, this becomes even more important—one person's contaminated utensil can affect the whole container.

Never leave mayo sitting out at room temperature for more than two hours. If you're making sandwiches for a picnic, keep the jar in a cooler with ice packs. After two hours at room temperature, bacteria can multiply to unsafe levels, and the emulsion can start to break down.

Homemade Mayonnaise Needs Different Rules

If you make mayo at home with raw eggs, vinegar, and oil, treat it as a highly perishable food. The USDA recommends using homemade mayo within one week, and that's only if you've kept it refrigerated the entire time. Some recipes use pasteurized eggs to reduce the risk of salmonella, which can extend the timeline slightly, but not by much.

The reason is simple: commercial mayo is made with pasteurized eggs and precise acid ratios that are tested for safety. Homemade versions rarely match that level of preservation. If you make mayo regularly, make smaller batches and use them quickly. Freeze it in ice cube trays if you want to extend its life—frozen mayo lasts several months—but thaw it in the refrigerator before use, and understand that freezing can affect the texture slightly.

What to Do When You're Not Sure

If your mayo has been open for longer than three months, or if you can't remember when you opened it, the safest choice is to replace it. A new jar costs a few dollars. Food poisoning from spoiled mayo—which can cause serious illness—costs far more in time, discomfort, and medical care.

Write the date you open the jar on the lid with a permanent marker. This takes five seconds and removes all guesswork. You'll know at a glance whether it's still within the safe window. Many people do this automatically with other condiments; mayo deserves the same treatment.

Frequently Asked Questions

Can I eat mayo that's been in the fridge for four months?

No. The two to three month window exists because that's when the risk of bacterial growth becomes significant. After four months, the emulsion may have broken down and harmful bacteria may have multiplied. Replace it.

Does unopened mayo last longer than opened mayo?

Yes. An unopened jar lasts until the printed expiration date, which is usually one to two years from the manufacturing date. Once opened, the clock resets to two to three months. Check your jar's label for the exact date.

What if mayo gets warm during a power outage?

If it stayed above 40°F for more than two hours, discard it. Temperature abuse can allow bacteria to multiply and damage the emulsion. When in doubt, throw it out—it's not worth the risk.

Can I freeze mayonnaise to make it last longer?

Freezing stops bacterial growth, so frozen mayo lasts several months. However, freezing changes the texture—it may become grainy or separate when thawed. Thaw it in the refrigerator and stir well before use. It works better in cooked dishes than in fresh applications like sandwiches.

Is mayo safe if it separates into oil and liquid?

A thin layer of oil on top is normal and doesn't mean it's spoiled. Stir it back in. But if the separation is severe—large pools of oil with a watery base that won't mix—the emulsion has broken down and the mayo should be replaced.