Most commercial mayonnaise is safer than people think, but only when handled correctly. Because it’s made with pasteurized eggs and added acids, it’s designed to resist bacterial growth—yet that protection has limits. Once opened, every dip of a spoon or knife introduces new microbes.
If the jar is then left out for more than two hours, especially in a warm kitchen, those microbes can multiply to dangerous levels. Storing it consistently below 40°F (4°C) is essential to slow this process.
Homemade mayonnaise demands even more caution. Without preservatives and often made with raw or lightly cooked eggs, it’s far more vulnerable to contamination and should go straight into the refrigerator and be used within a few days. Always use clean utensils, close the lid tightly, avoid temperature swings, and when in doubt about smell, texture, or color, throw it away. Your sandwich isn’t worth a night of food poisoning.
