During the winemaking process, many wines are filtered using a process called 'fining'. This removes unwanted particles and ensures the wine looks clear and bright rather than cloudy.
The fining process can use a number of methods and these define whether wine is classed as vegetarian or vegan. Historically, the most commonly used agents were albumin (egg whites), gelatin (animal protein), casein (a milk protein) or isinglass (fish bladder protein).
It is important to note that these are not additives to the wine but tiny traces may be absorbed.
Vegetarian (V): wines fined with casein and albumin are usually acceptable to vegetarians.
Vegan (VG): the above four methods are not used in vegan wines. There are a number of animal friendly products available for fining wine, the most commonly used are clay based products such as Bentonite.