[This case is a hypothetical]
Recently a patient asked if her chronic rhinitis could be causing her excessive fatigue. She reports that she has been successfully treated for sleep apnea and wakes up refreshed but still becomes excessively sleepy after about four hours of activity.
She has chronic postnasal drainage and trouble breathing through her nose.
So assuming she has no other determinable causes of the problem, I said it is worth empirically treating her presumed chronic allergic rhinitis. I offered referral to an allergist but she declined for insurance reasons.
And here are the resources I used to develop her treatment program: