The biggest concern is improper food handling and temperature control. Commercial mayonnaise is usually formulated with vinegar or lemon juice, creating an acidic environment that discourages the growth of many harmful bacteria. But once mayonnaise is mixed with ingredients such as chicken, potatoes, eggs, or pasta, the finished dish may become much more vulnerable to bacterial growth. That’s why mayonnaise-based salads and sandwiches containing perishable ingredients should not be left sitting at room temperature for extended periods.

Food safety guidance recommends keeping perishable foods refrigerated at 40°F (4°C) or below. As a general rule, these foods should not remain at room temperature for more than two hours, or more than one hour when temperatures exceed 90°F (32°C). The same two-hour rule should not automatically be applied to every jar of shelf-stable commercial mayonnaise; its handling depends on the manufacturer’s instructions. Once opened, however, commercial mayonnaise should generally be refrigerated as directed on its label.

Another overlooked habit involves using the same spoon for several different foods. Imagine spreading mayonnaise on a sandwich, touching meat or another ingredient with the utensil, and then dipping it back into the jar. This can introduce bacteria and food particles that were not originally present. Using clean utensils, closing the lid securely, and following the product’s storage instructions are simple ways to reduce contamination.

Homemade mayonnaise requires additional caution because it may contain raw eggs and lacks the standardized processing used for commercial products. Using pasteurized eggs reduces the risk of Salmonella, and homemade preparations should be refrigerated promptly. Remember that harmful bacteria do not always produce a noticeable smell or visible change, so appearance alone cannot determine whether food is safe. A few sensible kitchen habits can make a meaningful difference without turning an ordinary condiment into something to fear.

Have you ever left mayonnaise or a mayonnaise-based salad sitting out during a family meal without thinking about it?