It seems impossible that a liquid could contain animal-derived products, but some brands do. That’s because when it comes time to filter or refine the wine, certain “fining agents” are used to remove particles, yeast, protein, and cloudiness. These fining agents often include “blood and bone marrow, casein (milk protein), chitin (fiber from crustacean shells), egg albumen (derived from egg whites), fish oil, gelatin (protein from boiling animal parts), and isinglass (gelatin from fish bladder membranes),” according to PETA.
The good news? The site Barnivore lets you search companies so you can find a wine you like that doesn’t rely on bone marrow as filtration agent.