Is chronic sinusitis just an allergic reaction to something?

Crummy sinuses: Sinusitis is inflammation of one or more of the sinus cavities. Chronic imples a long duration. Although allergy can be a cause, so can non-allergic inflammation and chronic infection. Less common causes could include ge reflux (extra-esophageal reflu), NSAID sensitivity, or possibly a tumor.

Possibly: Chronic sinusitis is a condition in which there is locked up sinus disease in some of the paranasal sinuses. The paranasal sinuses open into the nasal cavity, so if allergies are causing swelling of the nose, the sinuses can be blocked which can possibly lead to chronic sinusitis. However, anything that causes nasal congestion can cause chronic sinusitis, not just allergies.