No animal stuff or eggs or dairy. But certain gums have an artificial flavoring, Aspartame, some people don't recommend.
Quoting form
http://waynesword.palomar.edu/ecoph13.ht…
According to Michael Redclift (Chewing Gum: The Fortunes of Taste, 2004), modern gum bases are made from vinyl resins or microcrystalline waxes, producing a synthetic rubberlike substance similar to that used for the cover of golf balls. These newer substances produce longer-lasting flavor, improve the texture, and reduce tackiness. According to www.wrigley.com, the Wrigley Company still uses natural rosin softeners in their gum base. In the United States, rosin is largely derived from southeastern pines, including longleaf pine (Pinus palustris) and slash pine (P. elliotti) grown in large plantations. Crude turpentine sap is distilled in order to separate the volatile essential oils called "spirits" from the nonvolatile diterpene residue called rosin.