Contrary to what most people believe, salads made with bottled mayonnaise are not more fragile than other foods. As with any food, you don’t want to leave it out more than two hours (and if it is very hot, make that one hour for all foods).
There is actually some evidence that commercial mayonnaise can help prevent or delay spoilage, thanks to vinegar, lemon juice and salt, which act as very mild preservatives. But again, never exceed the two-hour rule for any food.
For more information on keeping foods safe, see No-Risk Picnics.
Recipe in photo: Crunchy Buttermilk Coleslaw