Mayonnaise is a common household staple, used as both a condiment and an ingredient in many dishes. However, proper storage is important to maintain its safety and quality. Mayonnaise is made from oil, egg yolks, and an acid such as vinegar or lemon juice. While its acidity can slow bacterial growth, commercial varieties often also contain preservatives and pasteurized eggs, while homemade mayonnaise is generally more perishable.

Once opened, mayonnaise should be refrigerated to reduce the risk of bacterial growth. The USDA recommends keeping perishable foods at temperatures below 40°F (4°C) and avoiding leaving them at room temperature for more than two hours. In hot conditions above 90°F (32°C), the safe limit is reduced to one hour. Refrigeration slows bacterial growth and helps preserve the mayonnaise’s texture, flavor, and quality.

Leaving mayonnaise on the counter for too long can increase the risk of foodborne illness caused by bacteria such as Salmonella and Listeria. Spoiled mayonnaise may develop an unpleasant or rancid smell, changes in color or texture, separation, or visible mold. If any of these signs appear, it should be discarded. Shelf-stable individual packets are another option because they are designed to remain at room temperature until opened.

For the best safety and quality, mayonnaise should be refrigerated after opening and returned to the refrigerator promptly after use. If it has been left at room temperature for longer than the recommended limit, it is safer to throw it away rather than risk foodborne illness. Following these simple storage practices helps keep mayonnaise fresh and safe to eat.