Portillo's Guest Services confirmed by email that both the hot dog and hamburger buns contain soybean oil, that the House, Caesar and tartar sauces all contain soybean oil, and that the fry oil is a beef tallow and vegetable blend that can contain cottonseed oil. With the bun in nearly every order this is now a whole-menu problem rather than just a fryer one, and they still publish no per-item ingredient list.
Updated 2026-09-01 after Portillo's answered our email; originally rated 2026-08-26 off the FAQ alone. Diana in Guest Services replied 2026-08-28, verbatim: "Fry oil is a beef tallow and vegetable blend( can contain cottonseed oil)"; "Hot Dog and Hamburger buns both contain soybean oil"; "House dressing, Cesar dressing, and tartar sauce all contain soybean oil." She also said, verbatim, "I do not have a per item list of ingredients that I can share, if you like I can check specific menu items ingredient for you" - so a follow-up on named items is possible if we ever want it. That moves seed_oil from some to ALL: the bun is in nearly every order, both signature dressings and the tartar sauce are soybean, and the fryer blend can carry cottonseed. Additives and nova stay NULL - Portillo's still publishes no ingredient statements (portillos.com/nutrition serves NutritionAllergen_July2026.pdf, 490,579 bytes, calories and allergen icons only) and the email gave none.