Best Answer: The grossest part about marshmallows is most are made with gelatin. And here is what gelatin is made out of: Gelatin is made from by-products of the meat and leather industry, mainly pork skins, pork and cattle bones, or split cattle hides.That is reason enough to never touch them!!Good for you! Sugar or Corn Syrup * Egg whites * Gelatin-usually from animals bones or hides, Kosher gelatin is from fish There are Vegan marshmallows -- ones that use real marshmallow extract from the marshmallow plant or use gelatin alternatives.