Mayonnaise is a popular household staple, but many people wonder whether it belongs in the refrigerator or can safely sit on the kitchen counter. Proper storage is essential for maintaining its freshness and reducing the risk of foodborne illness.

Made from oil, egg yolks, and vinegar or lemon juice, mayonnaise has an acidic composition that helps slow bacterial growth. Commercial varieties often contain pasteurized eggs and preservatives, while homemade versions generally spoil more quickly because they lack these additional protections.

Food safety guidelines recommend refrigerating mayonnaise after opening and avoiding leaving it at room temperature for more than two hours. In hot conditions, this limit drops to one hour. Keeping it below 40°F (4°C) helps preserve its quality and slow bacterial growth. Leaving mayonnaise out for too long can increase food safety risks, including potential exposure to harmful bacteria.

Signs of spoilage include an unusual smell, discoloration, visible mold, or changes in texture. If mayonnaise appears spoiled, discard it rather than tasting it. To keep it safe, refrigerate it promptly after use, always serve it with clean utensils, and avoid leaving it on the counter for extended periods. Individually packaged, shelf-stable mayonnaise portions are another convenient option because they can remain unrefrigerated until opened.