Sinusitis is the medical term for a sinus infection, which causes inflammation of the sinuses due to chronic allergies, fungal or bacterial infection, or environmental or chemical sinus irritation. Sinusitis is characterized by type of infection. For instance, sinus infections can be acute or subacute, infectious or non-infectious, or chronic infections.

While individuals with sinusitis aren’t typically considered contagious, left untreated a sinus infection can be very serious and even life-threatening if it develops into one of the following:

• Zygomycosis, a rare fungal infection of the sinuses that demands emergency medical treatment.
• Osteomyelitis, which is characterized as an infection in a bone that spreads through the bloodstream.
• Meningitis, or a sinus infection that infects the rear central area in the head, eventually infecting the brain.
• Orbital cellulitis, which causes swelling in the eye tissues behind the orbital septum.
• A brain abscess, which infects the brain with a dangerous fungal, viral, or bacterial infection.

Sinusitis can often be mistaken for a common cold because many of the common symptoms are similar. Look for these telltale signs of sinus infection:

Is it flu or the common cold?
Patients often assume they have a common cold in the early stages of a sinus infection. However, the symptoms of sinusitis often stick around much longer and don’t respond to over-the-counter cold and flu medications. Don’t assume a stubborn headache, cough, nasal congestion, mild to high fever, and sore throat are signs of the flu.

Symptoms that don’t go away
Perhaps the most telltale sign of a sinus infection is cold and flu-like symptoms that don’t dissipate with fluids, rest, and use of over-the-counter (OTC) cold and sinus medications like decongestants. If symptoms persist, or worse, see a doctor immediately.

Stuffy nose and postnasal drainage
Sinus infections cause severe inflammation and congestion of the sinuses. Sinus blockage will often lead to postnasal drip in the back of the throat.

Discolored mucus
Discharge from coughing, sneezing, and blowing the nose is typically not clear, but cloudy yellowish or greenish, accompanying a sinus infection.

Face tenderness
Inflamed sinuses often lead to pain and tenderness in the sinuses area of the face. Patients may also feel pain in areas of the ears, teeth, and jaw.