By Audrina Bigos

(CBS) — There’s the golden rule. And then there’s the ‘no ketchup’ rule.

Now, a Chicago hot dog joint is going where none have gone before.

CBS 2’s Audrina Bigos reports.

Portillo’s is flipping the script in a new promotional video that outlines all of the condiments for a hot dog. The restaurant chain hedges a bit when it comes to ketchup.

“While ketchup doesn’t come standard, we will add it if you like,” the video says.

Them’s fighting words to Superdawg on Chicago’s Northwest Side, which dates back to 1948. The iconic drive-in observes the no-ketchup rule … for the most part.

Owner Don Drucker says if someone asks for the tomato paste, “You’ll have to do that yourself. We won’t apply it for you.”

He has a scientific explanation on why ketchup and Chicago-style dogs don’t mix: “The acidic nature of the ketchup detracts from all of those flavors that are combining in your mouth.”

Portillo’s, which is expanding to Florida and Wisconsin, said it created the video to explain to markets outside of the Chicago area exactly what is on a Chicago style hot dog. In an email, Portillo’s spokesman Nick Scarpino said:

“In the video we clearly state that a Chicago style hot dog does not come with ketchup. But at Portillo’s, the customer always comes first and if a customer asks for ketchup on a hot dog, we will put it on for them. Personally, my kids happen to love ketchup on their Portilllo’s hot dogs but I do not. You may find it interesting that mustard is not a standard topping on our burgers (ketchup and mayo are) but we’ll add mustard if someone would like it. Thanks for reaching out.”