Commercial mayonnaise is generally less hazardous than its reputation suggests. Most varieties contain pasteurized eggs and enough acid to discourage harmful bacterial growth. Those safeguards do not make every mayonnaise-containing meal safe, however: chicken, tuna, eggs, and other perishable ingredients still require careful handling. Refrigerate opened mayonnaise according to its label, keep your refrigerator at 40°F (4°C) or below, and use clean utensils to avoid introducing food scraps and contamination.

Homemade mayonnaise needs particular care, especially when prepared with unpasteurized raw eggs; choose pasteurized eggs and follow a reliable recipe’s storage guidance. Refrigerate perishable mayonnaise-based dishes within two hours, or one hour when temperatures exceed 90°F (32°C). Keep jars tightly closed, and discard anything moldy or otherwise spoiled. Remember that dangerous bacteria may cause no noticeable change in appearance, smell, or taste. When storage conditions are uncertain, throwing food away is safer than tasting it. Small precautions help protect everyone sharing your table.