Only situations with a published figure are listed. A blank isn't “forever” — it means no reliable number is published for it.
Storage
Store at: Cool, dark pantry unopened; refrigerate at 40°F (4°C) or below after opening
Refrigerate after opening: Yes — refrigerate at 40°F (4°C) or below
Tip: Commercial mayo is acidic and shelf-stable until opened; once opened it must be refrigerated. USDA FoodKeeper: 3–6 months in the pantry from purchase, 2 months refrigerated after opening. Refrigeration ensures that commercial sauces and condiments stay fresh for a longer period of time. Shelf-stable commercial mayonnaise is safe when stored at room temperature after opening. Quality, not safety, is the reason the labels on these products suggest that they be refrigerated after opening.
How to tell if Mayonnaise has gone bad
Sharp or sour smell
Oil separation that won't stir back in
Browning or darkening
Mold
These are the general spoilage signs for condiments & sauces — never taste something to test it. When in doubt, throw it out.
About 2 months refrigerated at 40°F (4°C) or below, according to USDA FoodKeeper. Refrigerate it once it's open.
Does Mayonnaise need to be refrigerated after opening?
Yes — keep Mayonnaise at 40°F (4°C) or below once it's open. Cool, dark pantry unopened; refrigerate at 40°F (4°C) or below after opening.
How can you tell if Mayonnaise is bad?
Look for: Sharp or sour smell; Oil separation that won't stir back in; Browning or darkening; Mold. Never taste something to test it — when in doubt, throw it out.