Stacker King: Allergens at a Glance
The honest verdict
Stacker King · Burger King
The Stacker King is a stacked burger from Burger King featuring two flame-grilled beef patties, American cheese, bacon, and a signature sauce on a sesame seed bun. The allergen profile is dominated by wheat from the bun, milk from the cheese and possibly the sauce, and egg from the mayonnaise-based sauce. The bun may contain sesame seeds. Soy is likely present in the sauce and as refined oil. Peanut, tree nut, fish, and shellfish are not typical ingredients. Cross-contact on shared grill surfaces is possible. The Stacker King is a distinct menu item from the Whopper (which has lettuce, tomato, and a different mayo-tomato sauce) and the Bacon King (which has a different sauce profile). Always verify with your specific Burger King location before ordering.
Allergen details change and vary by location. This is a general guide — always confirm with the restaurant before ordering. Not official or medical advice.
Key facts
Burger King's Stacker King features two flame-grilled beef patties, American cheese, bacon, and a signature sauce on a sesame seed bun.
The sesame seed bun is a direct source of both wheat (gluten) and sesame seeds, making it a double-allergen item for those with wheat and sesame allergies.
FDA — Food Allergen Labeling and Consumer Protection Act (FALCPA)
Mayonnaise-based sauces are a common source of egg allergen in fast-food burgers, including the Stacker King's signature sauce.
Every major allergen, one clear grid
Each of the nine major allergens marked for Stacker King at Burger King — Contains, May contain (cross-contact or varies), or Free. Anything we couldn't confirm defaults to "may contain," because a shared kitchen can't be ruled out without the restaurant's official menu.
- MilkContains
American cheese is a standard ingredient on the Stacker King. The signature sauce may also contain milk-derived ingredients. Confirm with the restaurant if ordering without cheese.
- EggContains
The signature Stacker King sauce is mayonnaise-based, which contains egg. Removing the sauce would eliminate this allergen.
- Wheat / GlutenContains
The sesame seed bun is wheat-based. There is no standard gluten-free bun option at most Burger King locations.
- SoyMay contain
Soybean oil is used in cooking and the signature sauce may contain soy lecithin or soy protein. Highly refined soybean oil is FDA-exempt from allergen labeling but may still be a concern for those with severe soy allergy.
- PeanutFree
Peanut is not an ingredient in the Stacker King or its components. Cross-contact is very unlikely in a standard Burger King kitchen.
- Tree NutFree
Tree nuts are not an ingredient in the Stacker King. Not typical in Burger King burger preparation.
- FishFree
Fish is not an ingredient in the Stacker King. Burger King's fish sandwich (Big Fish) is prepared separately, but confirm fryer practices if concerned about cross-contact.
- ShellfishFree
Shellfish is not an ingredient in the Stacker King and is not typical in Burger King kitchens.
- SesameMay contain
The standard bun for the Stacker King is a sesame seed bun. Sesame seeds are a direct ingredient on the bun top. Confirm with the restaurant if a sesame-free bun option is available.
“May contain” means cross-contact is possible or the answer varies by location — not that the allergen is a listed ingredient. For a severe allergy, treat “may contain” the same as “contains” until the restaurant confirms otherwise.
Small changes that remove an allergen
Simple modifications that can take an allergen off your stacker king. Always name your allergy when you order and ask staff to confirm — a modification only helps if the kitchen prepares it separately.
Order the Stacker King without cheese
Order the Stacker King without the signature sauce
Request a lettuce wrap instead of the sesame seed bun
Ask if a sesame-free bun is available
A modification lowers exposure but doesn't erase cross-contact from shared fryers, grills, or prep surfaces. For a severe allergy, confirm the prep with a manager before you eat.
Read this before you order
Cross-contact & severe allergies
A “free of” mark on the grid above means the allergen isn't an ingredient — it doesn't mean the item was made in an allergen-free kitchen. Two things matter most:
Shared fryers & equipment
Burger King flame-grills beef patties on a shared broiler surface. While the high heat reduces some risk, trace proteins from other menu items (including those containing milk, egg, or soy) could transfer. The bun is assembled on shared prep surfaces. Cross-contact risk is moderate — not as high as shared fryers, but present. Ask your location about their grill and prep area cleaning procedures.
If your allergy is severe
For anaphylactic allergy to wheat, milk, egg, or sesame, the Stacker King is not a safe choice without significant modifications (no bun, no cheese, no sauce) and confirmation of preparation practices. Even modified, cross-contact on shared grills and prep surfaces is possible. Carry your epinephrine auto-injector. If you cannot confirm safe preparation, consider a different menu item with fewer allergen risks.
This guidance is general and can't account for how any single location prepares your food. The restaurant's staff and official allergen menu are the final word — when in doubt, ask, or choose something else.
❓Frequently Asked Questions
No, they are different. The Whopper has lettuce, tomato, pickles, ketchup, and mayonnaise on a sesame seed bun. The Stacker King has two patties, American cheese, bacon, and a different signature sauce (which is mayonnaise-based but may have a different formulation). The Whopper's ketchup adds tomato-based ingredients but no dairy; the Stacker King's cheese adds milk. Both share wheat and sesame from the bun and egg from mayonnaise. The Stacker King is a higher-risk item for milk allergy due to the cheese.
Yes, the sesame seed bun is wheat-based and contains gluten. There is no standard gluten-free bun at Burger King. Removing the bun (ordering as a lettuce wrap or bunless) eliminates the wheat, but confirm that the beef patties are not seasoned with wheat-containing ingredients and that the grill surface is not shared with breaded items. Burger King's flame-grilled patties are typically gluten-free by ingredient, but cross-contact is possible.
Yes, ordering without the signature sauce removes the primary egg source (mayonnaise). However, confirm that no other egg-containing ingredients are present — the bun and cheese are typically egg-free. The beef patties are not breaded and do not contain egg. Removing the sauce is the most effective modification for egg allergy.
Removing the cheese eliminates the most obvious milk source, but the signature sauce may contain milk-derived ingredients. Ask the restaurant whether the sauce contains milk, whey, or casein. If the sauce is milk-free, a no-cheese Stacker King is likely safe for milk allergy by ingredient, though cross-contact on the grill surface remains a possibility. Always confirm with the specific location.
Both are stacked burgers with two patties, cheese, and bacon. The key difference is the sauce: the Stacker King uses a signature mayonnaise-based sauce, while the Bacon King uses a different sauce (often a smoky or BBQ-style sauce). The allergen profiles are similar (wheat, milk, egg, sesame), but the sauce formulations differ — check each sauce's ingredients separately if you have specific allergen concerns.
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Read moreFind out which foods you actually react to
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Please verify before ordering
Allergen info changes and varies by location
Recipes, suppliers, and preparation methods change often and differ between locations, so the details here can go out of date or not match your specific Burger King restaurant. Always confirm directly with the restaurant and check its official allergen menu before ordering. This page is a general research summary — it is not official information from Burger King, and it is not medical advice. If you have a food allergy, decisions about what is safe to eat should be made with the restaurant and, where relevant, your healthcare provider.