In fact, the acidity in mayonnaise can slow or prevent the growth of harmful bacteria, including Salmonella.
So Can You Leave It Out?
Technically:
Unopened jars can be stored at room temperature
Opened mayonnaise can sit out for short periods (like during a meal)
However, leaving it out for long periods is not recommended—not because it instantly becomes dangerous, but because quality and safety can decline over time.
Homemade Mayonnaise: A Different Story
Homemade mayonnaise is less stable.
It often uses:
Raw eggs (not pasteurized)
