Acute allergic sinusitis occurs when the lining of the nose and sinuses becomes inflamed. Common causes include pollens, animal dander, and other allergens. These allergens set off an inflammatory response. Histamine and other chemicals are released, causing the symptoms of acute allergic sinusitis. Viruses attack the lining of the sinuses and cause swelling of the nasal tissues, which leads to symptoms.
Bacterial sinusitis can follow a viral infection if bacteria grow inside the sinuses.
About 5 out of every 1,000 viral URIs are complicated by a bacterial sinus infection . Bacterial forms of sinusitis also occur when the drainage opening is blocked by swelling or narrowing. Then the normal bacteria in the sinus and nasal tracts overgrow and cause an infection. Cold air sinusitis produces symptoms when the person is exposed to cold air. Aspirin sensitivity sinusitis may occur in some individuals when they take medicines containing aspirin.