You might find yourself wondering whether mayonnaise does go bad and how one can determine that it’s already spoiled. You can tell that mayonnaise has gone bad if it has an acidic smell or its color has darkened. It’s also good to know the shelf life of mayonnaise. It strongly depends on whether mayo is a commercial or a homemade one. Your homemade mayonnaise doesn’t contain preservatives, so if you’ll store it in the fridge, it should be fine for a week or two. When it comes to a commercial mayo, it contains some preservatives so it should be fine for up to two months after being opened.