As Oak speaks, Bowser shifts from surprised to annoyed. He's right, of course, but Bowser has no intention of acknowledging or admitting that.

"Look, I'm sure you get how human and pokemon health work, but we Royal Koopas are made of tougher stuff. It's not like I can afford to stop working on figuring this place out because I'm a little sick."

"And yeah, flower petals. Not- not sure what that's about-" Bowser suddenly kneels and starts coughing again, this time more violently and onto the floor. Once again, blood and combustible petals that quickly ignite are coughed up, this time in slightly greater quantities.