To keep mayonnaise safe for consumption if it is not refrigerated it has to be kept from being contaminated. A perfectly clean utensil, (so you don't introduce bacteria), must always be used in the mayonnaise jar.to keep it from getting contaminated. When mayonnaise becomes contaminated or mixed with other foods that is when it needs to be refrigerated .I do refrigerate it on our boat because if multiple people are using it there might not be a guarantee that it has not been contaminated.