Homemade mayonnaise is deliciously fresh, but it is also one of those sauces that rewards caution. The biggest issue is not flavor loss alone; it is food safety. Because classic homemade mayo is usually made with raw egg yolk, it can become unsafe faster than many home cooks expect, especially if it is handled carelessly or left too long in the refrigerator.
The short answer: homemade mayonnaise is best used within 2 to 4 days when kept cold in a clean, tightly sealed container. If your kitchen is warm, your eggs were not very fresh, or the sauce has been sitting out during serving, stay closer to the 2-day mark. Store-bought mayonnaise is a different story because it is formulated and acidified for stability, so an unopened jar lasts much longer. Once opened, though, it still needs refrigeration and good hygiene to stay safe.
Why homemade mayo is riskier
The main concern is raw egg. Even if the risk is low in any single egg, raw egg yolk can carry bacteria such as Salmonella. Acid from lemon juice or vinegar helps, but it does not make homemade mayonnaise invincible. The emulsion is also sensitive to contamination from dirty utensils, double-dipping, or spooning it onto a warm dish and then returning it to the jar.
For that reason, homemade mayo should be made in small batches and kept cold at all times. Use a very clean bowl and whisk, and refrigerate it promptly after mixing. If you are serving it at a picnic, barbecue, or buffet, do not leave it out for more than 2 hours total. In hot weather, shorten that to 1 hour.
How long each type keeps
- Homemade mayonnaise: 2 to 4 days in the refrigerator, depending on freshness, cleanliness, and how it was handled.
- Store-bought, unopened mayonnaise: usually safe until the best-by date if stored according to the label.
- Store-bought, opened mayonnaise: keep refrigerated and aim to use it within about 1 to 2 months for the best quality, or follow the package guidance if it is stricter.
Those ranges are about quality and safety together. Store-bought mayo usually lasts longer after opening because its recipe is designed to be more stable and acidic, and it is made under controlled conditions. Homemade mayonnaise does not have that same margin of safety, so the clock starts ticking much sooner.
Signs it should be thrown out
Do not taste-test your way into danger. Throw homemade mayo away if you notice any of these:
- a sour, sharp, or otherwise off smell
- separation that does not come back together after stirring
- visible mold
- discoloration or an unusually dull gray tone
- a slimy, watery, or curdled texture
- any sign it was left out too long at room temperature
Also discard it if it was made with cracked, dirty, or very old eggs, or if someone dipped a used spoon back into the container after touching other foods. With mayonnaise, contamination history matters as much as appearance.
How to store it safely
Keep homemade mayo in a small glass jar or food-safe container with a tight lid, and store it on a refrigerator shelf rather than in the door, where temperature swings are greater. Always use a clean spoon, and never return leftover mayo from a serving bowl to the main container. If you want a safer option with a longer fridge life, make a version with pasteurized eggs or egg products, or buy pasteurized mayonnaise.
The rule worth remembering is simple: store-bought mayonnaise is built to last longer, but homemade mayonnaise is a quick-use sauce. If in doubt, toss it out. With raw eggs in the mix, being cautious is not wasteful; it is smart kitchen practice.