This is interesting ...all commercially-made Mayo is completely safe. "It doesn't even have to be refrigerated. No harm in refrigerating it, but it's not really necessary."...it's not the mayonnaise (as long as it's not homemade Mayo) that spoils in the outdoors. It's probably the onions, and if not the onions, it's the POTATOES. He explained, onions are a huge magnet for bacteria, especially uncooked onions. https://netcookingtalk.com/forums/threads/onions-and-mayonnaise.8086/