Mustard . . .

Dijon and horseradish-based mustards should be refrigerated, but others are OK to leave out if you prefer them at room temperature. Refrigerating yellow mustard will help maintain its flavor, but it doesn't contain any ingredients that spoil.

What happens if you don't refrigerate mustard after opening?

According to the official website for French's Mustard, “Dijon and Horseradish mustards will lose their distinct flavors if not refrigerated, so we encourage refrigerating both.”

What condiments do not need to be refrigerated after opening?

Refrigeration not needed

Common condiments that don't require refrigeration include soy sauce, oyster sauce, fish sauce, honey and hot sauce. Feingold says vinegars and olive oil (stored in a cool, dark place) are pantry-bound; coconut oil is actually best kept out of the fridge since it hardens below room temperature.