Refrigerate or Leave Out? The Truth About Mayonnaise Storage

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.