The production of wine is a delicate process that includes a range of factors to obtain the desired outcome. One step in the production of wine often includes a process called fining (or "clarifying"). The fining process requires a fining agent to be suspended into the vat where it will later be filtered out of the wine. Fining agents are typically either animal, carbon or clay-based products and are used to gather proteins or sediment within the wine to adjust impurities such as color, haziness, taste and/ or smell. Animal-based fining agents include gelatin, isinglass, egg whites, and casein. Different agents will be used based on the desired outcome of the wine.  Because the fining agent is filtered back out of the wine, the labeling of these additives are not required or regulated.
Wineries might use animal-derived products as finings to remove proteins, yeast, and other organic particles which are in suspension during the making of the wine. A fining agent is added to the top of the vat. As it sinks down, the particles adhere to the agent, and are carried out of suspension. The fining agent and the gathered particles then are removed either by filtering or through a settling process. Although the animal proteins are filtered out after the wine has been clarified, the use of animal products in the production goes against some vegan or even vegetarian diets, if those diets are driven by animal rights rather than health motivations.
For those vegetarians and vegans who seek to minimize animal exploitation wherever feasible, wine filtered with animal products such as isinglass or gelatin would not be suitable for a vegetarian diet. Similarly, the use of any animal products or byproducts in the fining process would not be suitable for a vegan diet of similar motivation. For those vegans motivated by perceived health benefits of avoiding consumption of animal protein, the use of these agents would not be problematic.
Examples of common animal products used as fining agents are gelatin, isinglass, casein and egg albumen. Bull's blood is also used in some Mediterranean countries but (as a legacy of bovine spongiform encephalopathy (mad cow disease)]]) is not allowed in the U.S. or the European Union.
The most common animal product used for fining is gelatin due to its potency and effectiveness. It takes only one ounce of gelatin to clarify 1,000 gallons of wine. Gelatin is made from the boiling of animal parts. Wine specifically responds best to type A gelatin, which is derived from the boiling of pigs skin. Gelatin is used in both white and red wines to fix haze/ color and to adjust the flavor or bitterness of the wine.
Isinglass is a form of gelatin derived from fish bladders. It is primarily used to clear white wines. Gelatin and isinglass both need to be used sparingly to prevent residual traces remaining in the wine due to their potency.
Casein is the main protein found in cow's milk. It makes up 80% of the proteins and is derived by first skimming milk of its fat, then a process of precipitation to separate remaining particles of the milk and in the end be left with casein proteins. Casein protein is used in both red and white wines to treat and prevent oxidation.
As an alternative to animal products, carbon, bentonite, a clay mineral), and polyvinylpolypyrrolidone are the most common to be used to clarify wine. Some vintners also let the wine's sediments settle naturally, a time-consuming process. In Australia, winemakers are required to list the use of potential allergens such as casein and albumin on the label but are not obliged to list the use of other non-vegan fining agents such as gelatin or isinglass. Some winemakers will boast on the wine label that their wine is unfiltered, because some wine connoisseurs prefer wine to be unfiltered.
It is not required for products to disclose whether they are vegan/ vegetarian or not. Even products that choose to label their products with titles, are not required to show proof that they are free of animal byproducts, animal testing, or any form of animal exploitation. In the United States, it is not required that alcohol labels disclose even major allergens. There was a proposal submitted by the Tax and Trade Bureau in 2006 to mandate the labeling of major allergens such as milk, eggs, and fish included in the production of wine (whether it is filtered out or not).
in 2011, Dr. Emilia Vassilopoulou published a study conducted by herself and her colleagues in an attempt to determine if allergens (milk, egg, and fish products used as fining agents) should be labeled on the packaging of the product. Their goal was to find, in a controlled environment, if people with certain allergens would have reactions after drinking wine that had been fined with said allergen. The findings showed no reactions through in-vitro methods, but had positive skin pricks tests in patients who consumed/ were allergic to wines fined with milk, fish, and eggs. The findings were so minimal, that they agreed that the labeling is not necessary. However, this does prove that their still are particles of these animal proteins leftover in the wine.