For fish avoidance, ask about nước mắm, nước dùng cá and chả cá: fish sauce, fish stock and fish cake. For crustaceans, ask about shrimp paste, prawns and crab, not only visible pieces. Bún quậy commonly uses seafood pastes; removing the squid topping does not turn its base into a seafood-free bowl. Bún kèn has fish and coconut as part of its identity.
Peanuts may appear in dipping sauces, gỏi cá trích and grilled dishes with scallion oil. “Không đậu phộng” means no peanuts; “không rắc đậu phộng” only asks not to sprinkle them on top. If a sauce has already been blended, scraping off a garnish cannot undo its ingredients. Ask for the recipe answer before ordering that sauce separately.
Gluten-free needs a similar ingredient-level discussion. Rice noodles do not establish that the stock, soy sauce or added fish cake is gluten-free. A bánh mì is normally wheat bread, while a rice dish can still have a sauce containing wheat. Avoid choosing by the starch alone. Photographing the exact packaged condiment can help the kitchen answer more concretely than a translated cuisine label.