Toss Your Salad Dressing Immediately If Notice These Signs Store bought dressing will last two to three months after opening if properly stored. The acidic vinegar based versions last longer than ones containing dairy. Quick and Easy Italian Dressing Real Housemoms How long do salad dressings last in the refrigerator after opening? Zia's Fat Free Sweet Italian Dressing Case (6 Bottles) DiGregorio's Italian Market Developing the definitive Italian Dressing recipe for @nytcooking was not a job I took lightly! To celebrate, I made a classic Italian chopped salad, which is not a salad I dress lightly!