it is a myth that mayo goes bad as quickly as thought because it contains salt/vinegar. If it was clearing and discolored/moldy yes. It should be kept cold after use. unopened can store for yrs. in hot sun usually the combination of starches (macaroni egg, veggies) is the culprit in salads. It is entirely possible today to get a contaminated batch too.(I make mine from my own eggs) chances are unless you are presenting heavy diarrhea, vomiting dehydration it probably not food poisoning. you may have already had a infection and it is coincidence.