Most cases of sinus infection are caused by bacteria, and fungal sinus infections are rare. Fungal infections require different types of treatment than bacterial infections because they do not respond to antibiotics.

Overgrowth of fungi can create fungus balls, or mycetoma, in the sinuses. Symptoms include chronic sinus pain and pressure, nasal congestion and drainage.

Fungi also can cause an allergic reaction resulting in polyps forming in the sinuses and nose. The primary sign of this infection is chronic nasal congestion and inflammation, often on only one side of the nose.

Individuals with an impaired immune system are more likely than other people to develop a life-threatening condition called invasive fungal sinusitis. Sufferers feel very ill, with symptoms of sinus pain, cough, fever and pus discharge from the nose.

Invasive fungal sinusitis can spread to the eye socket, resulting in a bulging eye and permanent loss of vision. It also may progress to the brain and central nervous system, especially if not treated promptly.

Treatment of fungal sinus infections includes surgery to remove the fungus. Allergic fungal sinusitis and invasive fungal sinusitis also require intensive medication.