Dragon Sinus Infection
Grabon and the other dragons aim snot at one another and their human friends in a display of disgust and disagreement in a hard snort. This is an action that elicits a strong reaction from female dragons, non fighting male dragons, and most humans. But imagine if they had a sinus infection and the snot thickened. Yes that would make a gross expression of disgust so much worse.
Knowing that dragons and humans are susceptible to the same diseases and that the same remedies work cross species, it would be surprising if dragons did not occasionally get a sinus infection. I can just imagine some of my dragon friends with an illness that clogged up their ears and made their heads feel like it might split. All the while their eyes had pressure building up behind them.
Sinus infections make my ears crackle, it throws off my balance, and fuzzes my thoughts. Somehow I don’t think flying would be good, not to mention the effects of the pressure changes as they rode air currents at different elevations. Have you ever flown in a plane with a stuffy head and ears? So. Not. Fun!
So a dragon with a sinus infection would be grounded, have a splitting headache, and would need to continually clear the nasal channels as they drank plenty of fluids. Very unpleasant for a dragon.