Speaking of class, House is at home, trying to pee. Holding a hot water bottle somewhere in the vicinity of his deal doesn't help. He takes some Vicodin. I...don't really care about House's peeing issues.
Foreman walks into the sleep lab and finds no one watching Sgt. John, who has woken up and is calling out for assistance. Foreman asks him what's wrong, and John says that there's a horrible smell in the room. Foreman doesn't smell anything, but he does see something: John's tongue is covered in white slime. The Magic Schoolbus Cam makes a token appearance to show us a bunch of microscopic white tentacled things swimming around in the goo on John's tongue, and Foreman says that the smell is coming from Sgt. John's mouth. At this point, Cameron and Chase rush in, all disheveled and sweaty. Sgt. John looks really ashamed of his disgusting breath, as well he should. It's called an Altoid, John.
House spends a leisurely night in soaking in a hot, hopefully-piss-inducing bath, swallowing Vicodins, and reading through military magazines looking for pictures of Sgt. John. I wonder why House has all those military magazines at his home. I'm sure Wilson knows the answer to that. House is also wearing glasses, in the tub, that I'm sure some people will find incredibly attractive. House's cell rings. It's the Cottages, reporting that there is indeed something wrong with Sgt. John: he has bacterial vaginosis. In his mouth. Sick!!! Also, now I have to Google "bacterial vaginosis" and I just know someone's going to see that in my Google search history and get the Wrong Idea. But Sgt. John claims that he hasn't had oral sex in a year. "Selfish bastard!" says House. Foreman explains that Sgt. John hasn't been with anyone since his girlfriend dumped him when he went to Iraq. "Selfish bitch!" House cries, always happy to have a reason to call people names. He wants to know who the ex-girlfriend is, while everyone else wants to know how a guy can get bacterial vaginosis in his mouth without oral sex. Foreman thinks it's cancer, and that the vaginosis is an "opportunistic infection." So now cancer can give you bad vagina breath on top of everything else? That's rough. House agrees, and tells them to tell Wilson to biopsy Sgt. John's salivary glands. While they're waiting for those results, they're to get Sgt. John's dating history, even though that's obviously irrelevant to the case.
Wilson tells Sgt. John that the antibiotics they're giving him should make that vaginosis go away soon. You'd think that, but I'm going to tell you right now that Sgt. John will have crusty white stuff around his mouth for the rest of the episode, so you can prepare yourself for that nastiness. With that, Wilson starts the biopsy process while Sgt. John whines that he was one of the only guys in his unit who didn't chew tobacco, and now he's the one who has mouth cancer. Wilson says that this kind of cancer is "very treatable if caught early." Sgt. John is pretty sure that this isn't early, seeing as he's spitting smelly white goo out of his mouth.