You Might Be Keeping Mayo Way Too Long—Here’s How to Know if It's Still Good

When it comes time to stock up your pantry and fridge for all of your favorite summer recipes, a jar of mayonnaise will likely be on your list. The thick, creamy condiment, made by emulsifying egg yolks, oil, and an acid such as vinegar or lemon juice, is an essential ingredient in classic cookout sides like creamy coleslaw, potato salad, and broccoli salad, as well as dips like homemade ranch dressing and party appetizers like deviled eggs.

Whether you’re using mayo to whip up a traditional chicken salad or brown bread for a classic grilled cheese, you may wonder why mayo has a bad reputation for causing foodborne illnesses. According to the USDA, however, other ingredients are likely to blame, as the acid in mayonnaise (such as vinegar or lemon juice) tends to prevent bacterial growth. That said, there are definitely some rules you should follow when it comes to storing and using mayonnaise.

We tapped two nutritionists, Taylor McClelland Newman, M.S., R.D., of Nourished by Taylor in San Antonio, Texas, and Molly Snyder, R.D.N., L.D.N., of Full-Filled Nutrition in Pittsburgh, Pennsylvania, to weigh in. Keep these tips in mind the next time you grab some mayo to slather on a classic BLT during the height of tomato season.

How Long Does Mayonnaise Last in the Fridge?

Both of our experts agree: Store-bought mayonnaise can be stored in the refrigerator for about two months after opening. Newman says to check for signs of spoilage, such as a strong odor or discoloration. When it comes to homemade mayonnaise, the shelf life is much shorter—it will only last about a week in the fridge. “Homemade mayo may be made with raw eggs and often lacks the preservatives found in store-bought versions,” Newman says. “Therefore, it is recommended to store it in the refrigerator and use it within four days of preparation.”

How to Store Mayonnaise

Keep that jar of mayonnaise good for as long as possible by following proper storage guidelines. Unopened mayonnaise can be stored in a cool, dry place, like the pantry, until you're ready to use it. Once opened, Newman says it’s best to keep mayonnaise in the refrigerator at 40°F or lower. In these conditions, mayonnaise will typically keep for about two months or until the expiration date on the label.

“Summer is here, and as outdoor parties and barbecues become more frequent, it's important to keep food safety in mind concerning mayo,” Newman says. “If you are indoors or in temperatures below 90 degrees Fahrenheit, mayo can sit out for up to two hours. However, if the temperature exceeds 90 degrees, that window is reduced to just one hour.”

Signs of Spoilage in Mayonnaise

When in doubt, throw it out, especially if your jar of mayonnaise is showing any classic signs of spoilage. Newman recommends keeping an eye out for these telltale signs:

• Changes in color
• A sour smell
• Visible signs of mold
• Texture changes like lumpiness or separation