My answer: Angela M. Fraser, Ph.D. of the Department of Family and Consumer Sciences, notes on their site, “Mayonnaise-based foods need to be kept cold. Mayonnaise alone is too acidic for bacteria to grow in it. However, when mayonnaise is mixed with other foods, (particularly those that have been handled a lot and/or are protein foods), bacteria can grow if this mixture is kept too warm.”
I personally will go with refrigerating my mayo, partially habit and for safety. Besides, just like Mom, I put eggs in my potato salad and I don’t want to take the risk of getting sick. You know what I’m talking about if you’ve ever had food poisoning. Does it really hurt anything to keep most things refrigerated? Dr. Fraser’s paper is worth the read for information on various picnic foods.
Here’s more from snopes.com about mayonnaise. I’ll go with what “Tiggress” (about the 6th person down the list) has to say because there are things mixed in with the mayonnaise that might spoil quicker than the mayo itself, which could result in a problem. CHOW offers current information on the “debate on refrigerating mayonnaise or not.” If there’s any question, why not just refrigerate mayonnaise-based foods like potato salad that contain mayonnaise just to be on the safe side? Thanks for your question and for your interest in Ask Cynthia a Question.