Finnish probiotics brand Gefilus is so good at building up healthy bacteria in your gut—thereby strengthening your immune system—that you could lick a pay phone in Moscow and not get sick.

That's the rough premise of a 22-minute (!) ad from dairy conglomerate Valio.

To illustrate the effectiveness of its product, the marketer hired travel television host Ian Wright, known for his willingness to eat just about anything, to bounce around the globe with a germ-measuring meter.

Along the way, he slides his tongue across the filthiest surfaces he can find while maintaining a steady Gefilus diet to boost his body's internal defenses.

It's a strong contender for the grossest ad of 2016, with Wright taking on some truly rancid challenges. To his credit, he draws the line at the handle of a public bathroom stall in Moscow, though it's not really clear that would be worse than some of the other surfaces he's willing to taste.

Horror-gaping aside, it actually manages to be surprisingly entertaining, and perhaps even informative. The documentary-style ad, charmingly if goofily titled "The Lick-Hikers Guide to Inner Strength" and created by Hasan and Partners Helsinki, features interviews with doctors and academics, and cute little animations on Valio's vision of the science of probiotics.

Licking dirty things is pretty rare—though not unheard of—as an advertising theme, and no wonder. Still, Wright's humor about the dubious sanity of the undertaking makes him endearing, even as he samples filthy river water in Helsinki, or the flush button in a train bathroom.

Ultimately, the highest concentration of germs he finds is in his home kitchen sink—though as the credits roll, he measures a certain part of his own person that, perhaps unsurprisingly, is not far behind.

Whether Gefilus can really turn your gut into an iron fortress is another question; it goes almost without saying that Wright's tests aren't exactly a convincing experiment. But one thing is for sure: Don't try this at home. Not that you'd want to.