The sinuses are hollow spaces in the skull and the face bones around your nose. There are four pairs of sinuses, named for the bones that they're located in:

  • The maxillary sinuses are located on each side of your nose, near the cheek bones.
  • The frontal sinuses are located above the eyes, near your forehead.
  • The ethmoid sinuses are located on each side of the bridge of your nose, near your eyes. There are three small pairs of the ethmoid sinuses.
  • The sphenoid sinuses are behind the eyes, deeper into your skull.

These sinuses collectively are called the paranasal sinuses.

The name sinus comes from the Latin word sinus, which means a bay, a curve, or a hollow cavity.

  • Frontal sinuses: The right and left frontal sinuses are located in the center of the forehead (frontal bone) just above each eye.
  • Maxillary sinuses: These are the largest of the sinuses and are located behind the cheekbones near the maxillae, or upper jaws.
  • Sphenoid sinuses: The sphenoid sinuses are located in the sphenoid bone near the optic nerve and the pituitary gland on the side of the skull.
  • Ethmoid sinuses: The ethmoid sinuses are located in the ethmoid bone, which separates the nasal cavity from the brain. These sinuses aren't single sacs but a collection of 6 to 12 small air cells that open independently into the nasal cavity. They're divided into front, middle, and rear groups.

The sinuses are part of your nose and respiratory system. They connect to your nasal passages in a complex network of air flow and drainage passages.

As you breathe in air through your nose and mouth, it moves through the sinus passages. The sinuses also produce mucus that coats and lubricates your nasal passages and the sinuses themselves.

Both air and mucus flow through your sinuses and drain into your nose, through tiny openings called ostia (or singular, ostium).

Little hairs called cilia help the mucus move through the sinus cavities. The mucus from the sinuses drains into your nasal passages and then down the back of your throat to be swallowed.

The draining mucus helps keep your nose moist and it filters out dust and bacteria.

The sinuses also:

  • give your voice resonance as the air vibrates
  • help protect your face in case of trauma
  • insulate against rapid temperature changes in the nose
  • provide an immunological defense

Any infection of your upper respiratory tract can easily spread to the sinuses. The resulting inflammation and pain is called sinusitis. It's also known as rhinosinusitis.

Your sinuses can become infected by bacteria, a virus, or both.

Sinus infections are common and can be a major health problem. According to the American College of Allergy, Asthma & Immunology (ACAAI), 31 million people in the United States have sinus infections at a given time.

You're at higher risk for sinusitis if you:

People often develop sinusitis after they have a common cold. If the lining of your sinuses becomes blocked in a cold, the mucus gets thick and sticky. Your sinuses may not drain properly and bacteria can then build up in the mucus.

Infections of the maxillary sinuses are most common.

Symptoms of sinusitis

Symptoms of a sinus infection are similar to those of a cold:

  • Depending on which sinuses are infected, you may feel pain or pressure in your forehead, cheeks, ears, or teeth.
  • You may have thick, sticky mucus coming from your nose.
  • Your mucus may be cloudy, or have a greenish-yellow color.
  • Mucus may drip down the back of your throat (postnasal drip), giving you a sore throat and cough.
  • Your nose may be stuffed, restricting your breathing.
  • Your face may feel tender, especially around the eyes.

Other symptoms include:

  • hoarseness
  • fever
  • fatigue
  • bad breath
  • decreased sense of smell and taste

A sinus infection can last from 10 days to as long as 8 weeks. This is called an acute sinus infection.

Sometimes a sinus infection can become chronic, getting better and then worse again, off and on for months.

Chronic sinusitis is medically defined as sinusitis that occurs more than four times a year. If your sinus infection lasts longer than eight weeks, it's also usually considered chronic.

Chronic sinusitis is one of the most common chronic conditions.

The symptoms of acute and chronic sinusitis are similar. Fever is less likely, except in severe cases.

Factors involved with chronic sinusitis include:

Acute sinusitis care tips

Try moist heat or steam. You can make a steam inhaler by putting hot water in a bowl and inhaling the steam. To do this:

  1. Keep at least 8 inches away from the water so that you don't burn yourself.
  2. Inhale for about 2 minutes.
  3. Create an enclosed space for the moist, warm air to collect by draping a towel over your head as you lean over the bowl.

You can also buy a vaporizer, which creates steam from heat.

Other tips to manage symptoms:

  • Take over-the-counter (OTC) pain medication to ease headaches.
  • Try OTC drugs such as guaifenesin (Mucinex) that thins your mucus, which can help to pass the mucus and lessen congestion.
  • Try acupuncture; there's some evidence that it's useful for sinus-related symptoms.

Chronic sinusitis care tips

Discover and treat the condition that's causing it. If another condition is associated with your chronic sinusitis, get treated for it and stick to your medications or treatment plan.

Try treatments or management plans if it's from allergies. See an allergy doctor to identify and have ongoing treatment for allergies.

There are treatment options like immunotherapy. And there are other ways to manage allergies — your doctor may also advise you on specific antihistamines to take to reduce your allergy symptoms.

If you're sensitive to aspirin, see a doctor. You might be a candidate for desensitization treatment.

Learn about different antihistamine and decongestant options. Before you take over-the-counter (OTC) nasal decongestants or antihistamines, it's a good idea to consult with a doctor.

Some OTC drugs may thicken your mucus and make it harder to drain. These include:

  • diphenhydramine (Benadryl)
  • loratadine (Claritin)
  • cetirizine ( Zyrtec)

Talk with a doctor about corticosteroids. Your doctor may prescribe corticosteroids in nasal spray form to treat and prevent inflammation. If your condition is severe, they may prescribe oral corticosteroids.

Consider antibiotics if it's a bacterial infection. If your infection is bacterial, a doctor can prescribe an antibiotic.

Understand your individual sinus anatomy. In some cases of chronic sinus infections, surgery is an option to remove tissue or a polyp if that's blocking a nasal or sinus passage.

Recognize and try to avoid inhaling irritants. Stay away from known irritants, such as tobacco smoke.

Try a nasal rinse or spray. Use a nasal saline spray or solution to irrigate your nose and reduce irritants.

You can take some steps to help keep your sinuses healthy and avoid sinusitis:

  • Keep your hands clean.
  • Maintain moisture in your nose and sinuses.
  • Drink plenty of fluids to keep your mucus thin.
  • Use a humidifier in the winter season, when the air tends to be drier.
  • Use an OTC nasal saline spray to irrigate your nose.
  • Use a neti pot to irrigate your nose and loosen mucus. Be sure to use distilled water or water that's been boiled, not plain tap water.
  • Keep the dust level down by dusting and vacuuming often, especially in the bedroom.

The good news is that if you're otherwise healthy and your sinusitis is caused by a virus, it's likely to resolve on its own within 7 to 10 days.