What Causes Acute Sinusitis?

The most common direct cause of acute sinusitis is bacteria. The role of bacteria or other infectious agents is complicated in chronic sinusitis. They may play a direct, an indirect, or, in some patients, infectious agents may not play any role at all.

Sinusitis is most often an acute condition, which is self-limiting and treatable. In some cases, the inflammation in the sinuses persists or is chronic.

A flu or cold virus could lead to acute sinusitis. Viruses themselves do not usually cause sinusitis directly. They create conditions for bacterial growth, by causing inflammation and congestion in the nasal passages (called rhinitis) that leads to obstruction in the sinuses. Rhinitis is the precursor to sinusitis in so many cases that many now refer to most cases of sinusitis as rhinosinusitis.

Sinusitis affects the following sinuses:

• The maxillary sinuses (behind the cheekbones) are the most common sites.
• The ethmoid sinuses (between the eyes) are the second most common sites affected by colds.
• The frontal sinuses (behind the forehead) and
• The sphenoid sinuses (behind the eyes).

Though colds cause inflamed sinuses, less than 5% of people with colds develop true sinusitis.

Fungal infections can be very serious, and both chronic and acute fungal sinusitis require immediate treatment. Fungal ball is not invasive and is nearly always treatable.

Fungal infections should be suspected in people with sinusitis who also have diabetes, leukemia, AIDS, or other conditions that impair the immune system. Fungal infections can also occur in patients with healthy immune systems but they are far less common.

Viral Sinusitis. Viruses are directly implicated in only about 10% of sinusitis cases.