Infection or Allergy?

I have had sinus inflammation for the past two months.  It started with a 24-hour-type stomach virus and seemed to progress to sinus pressure with severe post nasal drip.  I have been to two ENT doctors who have used an endoscope to look around.  Both said that they see inflammation but no signs of infection.  As a result, they attribute this to allergy and stress.  

How conclusive is the visualization of the sinus in determining infection?  Are there any other tests that can or should be done?  

Thanks,
-Jaco

[Vivek V Gurudutt, MD]

Nasal endoscopy (or looking in the nasal cavity with a scope) is an invaluable tool in assessing sinus and nasal disorders.  Many times, sinus infections can be diagnosed by seeing pus emanating from the sinuses or draining in the nasal cavity.  Although the drainage into the nasal cavity can be seen, visualization into the sinuses may not be possible.  It is not unheard of to have viral infections with lingering sinus inflammation, drainage, and pressure.  Other avenues to aid in assessment include radiological imaging of the sinuses.