Salad dressings in different jars
The Quick Ways To Tell If Homemade Salad Dressing Has Expired
Most commonly, salad dressings come in one of two forms — mayonnaise- and oil-based — each with their own unique properties that affect how quickly they spoil.
For a mayo-based dressing, look for separation in the refrigerator. Since the ingredients are whisked together, separation means the dressing has expired and should be tossed.
Oil-based dressing is different because it tends to separate anyway. This kind of salad dressing will give off a noticeable rancid smell if it’s expired, so make sure to check.