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.
USDA FoodKeeper tip (pantry storage): Refrigeration ensures that commercial sauces and condiments stay fresh for a longer period of time.
USDA FoodKeeper tip (pantry storage): Shelf-stable commercial mayonnaise is safe when stored at room temperature after opening.
USDA FoodKeeper tip (pantry storage): 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
USDA FoodKeeper publishes no spoilage note for Mayonnaise specifically, so these are the general signs for condiments & sauces — never taste something to test it. When in doubt, throw it out.
Air and warmth are what shorten an opened item's life — the right container buys back the days the packaging gives up once the seal's broken.
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. Those are the general signs for condiments & sauces — USDA FoodKeeper publishes no spoilage note for Mayonnaise specifically. Never taste something to test it — when in doubt, throw it out.