Altoids were my favorite mint behind Tic Tacs, but much like them they are and in this case somewhat shockingly to me, not vegan.
Original Peppermint Altoids are not vegan because they contain Gelatin, an animal product made from boiling animal bones. Gelatin is also often found in many other products, such as marshmallows or gummy worms as well.
The full ingredients on Altoids are: Sugar, Gum Arabic, Oil of Peppermint, Gelatin, and Corn Syrup.