Last updated: Jan 15, 2009
A cold usually lasts two to three days, but a sinus infection can linger for a week or longer.
At least once a year, Anna Lord, a 32-year-old from Seattle, has "almost unbearable pain" behind her eyes, cheeks, and forehead. Sometimes she has sinus drainage, and occasionally the discomfort arrives with a low-grade fever. Her symptoms often occur after she has had a cold or allergy symptoms. She rarely takes antibiotics, preferring to rest and soldier through her sickness.

Lord is prone to acute bacterial sinusitis, a form of sinus infection. Each year, about 31 million people experience sinus infections, which are usually caused by bacteria growing in the sinuses, the bony cavities found behind the nose, eyes, brows, and cheekbones. Typically, a cold or allergy attack causes mucous membranes in the sinuses to swell and block the tiny openings into the sinuses, which interferes with their ability to drain. The trapped mucus allows bacteria to breed, causing pain and pressure in the head and face.

All told, sinus infections cause 73 million days of "restricted activity" in the United States each year, according to a 1997 report from the Centers for Disease Control and Prevention. People with colds, which are caused by viruses, often mistakenly believe they have a sinus infection. While antibiotics can be helpful for those with sinus infections, they are useless when it comes to fighting cold viruses.

"The distinction can be difficult and no one rule applies to everybody," says Neil Bhattacharyya, MD, an associate professor of otology and laryngology at Harvard Medical School, in Boston. "Only about 2% to 6% of common colds progress to become a true bacterial sinus infection that could benefit from antibiotics."

Sinus infection or cold?
While the symptoms may be similar, there are some differences between the two conditions that can help you determine which one you have.

The main difference between the symptoms of a cold and sinus infection is how long they linger. Dr. Bhattacharyya says cold sufferers typically have a runny nose for two to three days, followed by a stuffy nose for two to three days. After that, most people begin to feel better. A sinus infection will hang around for seven days or more.

A fever may also signal a bacterial infection. As Lord can attest, sinus infections are sometimes accompanied by a low-grade fever, while colds typically are not. Other viruses (such as the flu) do cause fevers, however.

Another potentially helpful sign is the color of your nasal discharge. Unlike colds, which generally produce clear mucus, bacterial infections can produce greenish or yellow mucus. However, viruses sometimes produce colorful discharge as well, so this isnt considered a fail-safe test.

Dr. Bhattacharyya says there is no rhyme or reason as to why some people tend to develop sinus infections and others dont. But some people have nasal polyps or other problems, including allergies, which can increase their risk of chronic sinus infections.

How to treat a sinus infection
For most people, there are some preventive measures that can help stave off a sinus infection, or, if one occurs, to help relieve symptoms, says William Marshall, MD, an infectious disease specialist at the Mayo Clinic in Rochester, Minn. He recommends the same things "mothers recommend for a cold," like rest, drinking lots of fluids, breathing steam, and irrigating the sinuses with saline spray or a neti pot, a container used to rinse the sinuses with saline solution.

More about cold, flu, and sinus
Over-the-counter decongestants can also be helpful, but Dr. Marshall says they should not be used for more than three days because some products can exacerbate congestion and raise patients blood pressure and heart rate.

Bacterial sinus infections typically last for about 14 days, but the use of antibiotics speeds up the recovery process by up to five days. Still, according to Dr. Bhattacharyya, about 70% of sinus infections resolve on their own, and many patients, like Lord, prefer to let them run their course.

"Antibiotics mainly help to speed up the healing process," Dr. Bhattacharyya says. "But before antibiotics were around, people werent dropping dead of sinus infections and they still arent."

If left untreated, however, sinusitis can cause permanent damage to the sinuses and, in very rare cases, can lead to meningitis, Dr. Marshall says. If patients miss work or other activities due to sinus infections, or if their symptoms recur frequently, they should see a doctor for evaluation.