A sinus infection in most cases is almost harmless, although you do become uncomfortable and sometimes experience pain. If symptoms become very severe, antibiotics generally eliminate further problems. In rare cases, however, sinusitis can be very serious and can occur with complications.

The most common complication of sinusitis is chronic sinusitis. This can develop from severe cases of acute sinusitis. The symptoms of this complication are almost the same as to those of the acute condition, but they last longer and can keep coming back within a long period of time.

If you have chronic sinus problems, your doctor may refer you to an ENT specialist who will carry out some tests to determine the underlying cause. Depending on the outcome, you may be given a steroid spray or nasal drops to reduce the inflammation or a longer course of antibiotics in order to prevent infection from recurring. If these treatments for chronic sinusitis do not work, surgery to improve the drainage of the affected sinus may be recommended.

In extreme cases, other complications of sinusitis include the following;

• Asthma flare-ups. Acute sinusitis can trigger an asthma attack.

• Osteomyelitis. One important complication is infection of the bones (osteomyelitis) of the forehead. Adolescent males with acute frontal sinusitis are at particular risk for severe problems. In such cases, the patient usually experiences headache, fever, and a soft swelling over the bone known as Pott's puffy tumor.

• Infection of the eye socket. Infection of the eye socket, or orbital infection, which causes swelling and subsequent drooping of the eyelid, is a rare but serious complication of ethmoid sinusitis. In these cases, the patient loses movement in the eye, and pressure on the optic nerve can lead to vision loss, which is sometimes permanent. Fever and severe illness are usually present.

• Aneurysms or blood clots. Infection can cause problems in the veins surrounding the sinuses, interfering with blood supply to your brain and putting you at risk of a stroke.

• Vision problems. If infection spreads to your eye socket, it can cause reduced vision or even blindness. This is a medical emergency that requires immediate treatment to prevent potentially permanent damage.

• Ear infection. Acute sinusitis may occur along with an ear infection.

• Ischemic Stroke. One small and preliminary study found a link between ischemic stroke and sinusitis. More research is needed to determine if this possibility is valid.

• Meningitis. This is an infection that causes inflammation of the membranes and fluid surrounding your brain and spinal cord.

• Respiratory sinus arrhythmia (RSA), a change in the heart rate that corresponds to the frequency of respiration. Heart rate increases during inspiration and decreases during expiration. A respiratory infection is one of the causes of RSA.

• Widespread Infection. The most dangerous complication of sinusitis, particularly frontal and sphenoid sinusitis, is the spread of infection by anaerobic bacteria to the brain, either through the bones or blood vessels. Abscesses and other life-threatening conditions may result. In such cases, the patient may experience mild personality changes, headache, altered consciousness, respiratory problems, sinus bradycardia and, finally, seizures, coma, and death