A cough from a head or chest cold is likely to last longer than you think, a new study finds. That means you usually don't need antibiotics for a lingering cough, researchers said. The study included nearly 500 adults. As part of a poll, they were asked how long they expected a cough to last. People estimated about 7 to 9 days. Researchers compared these answers with the results of 19 studies on treatment of coughs. The studies showed that, on average, an untreated cough lasts about 18 days -- twice as long as people who were polled thought. Researchers said people who think their cough should be gone quickly are more likely to ask for an antibiotic when it hangs on longer. But most coughs are caused by viruses. Antibiotics don't treat viral infections. They only treat infections caused by bacteria. People may think an antibiotic helped when the illness was actually getting better anyway, researchers said. Using these drugs when they are not needed increases the risk that bacteria will become able to resist treatment. The journal Annals of Family Medicine published the study January 14. USA Today and HealthDay News wrote about it.

By Howard LeWine, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

Many people think that a cough related to a chest cold should last a week or less. And when it continues beyond five or six days, the common conclusion is: "I need an antibiotic."

In fact, the results of this study show that such coughs most often last twice as long. And it's common for them to last three weeks. Sometimes a cough from a chest cold can linger for a couple of months.

The actual infection doesn't last that entire time. Your immune system usually knocks out the germ within four to five days, if not sooner.

The infection is gone. But the irritation of the airways takes time to heal. And this makes the cough persist.

This discrepancy between how long a cough actually lasts and how long most people think it lasts is one of the big reasons for overuse of antibiotics for chest colds. Many people also think that a lingering cough means a bacterial infection. But the germ involved is almost always a virus. Antibiotics don't kill viruses.

Another reason that antibiotics are used too often for chest colds is terminology. Most people and their doctors call upper airway inflammation bronchitis. Technically, that is correct.

But here is the problem. If a person is diagnosed with acute bronchitis, he or she usually expects to get a prescription for antibiotics. Until recently, about 65% of patients visiting a doctor for a cough left the office with an antibiotic prescription.

I personally like the term chest cold rather than acute bronchitis or upper respiratory infection. Most people know that colds are caused by viruses. So there is less chance that a patient will ask for an antibiotic to treat a cold.

The authors of the article in the Annals of Family Medicine used the term "acute cough illness." I like that, too. But it's a new term. And it won't resonate with most patients.

What Changes Can I Make Now?

Coughing is one of our basic defenses against diseases. It expels mucus, germs and foreign particles from getting down into the lower airways and lungs. Coughing protects the lungs from infection and inflammation.

But who hasn't had too much of a good thing? When the hacking becomes relentless, it can keep us up, wear us out and lay us low.

It's no wonder that we spend roughly $3.5 billion each year on cough remedies. But how do you choose among the dizzying number of cough and cold products? There are all sorts of combination pills, capsules and syrups. Each product claims it's better than the one sitting next to it on the shelf.

If your main reason for the cough is nasal congestion with post-nasal drip, you can get relief from a decongestant. The most effective one is oral pseudoephedrine. Generic versions work just as well as the more expensive Sudafed.

If you choose a nasal decongestant spray, don't use it for more than three or four days. Your nose quickly gets used to it. Using it too long results in rebound congestion when you stop.

Expectorants and cough suppressants don't help much for coughs caused by chest colds. In general, they are safe when used as directed.

You will do just as well, though, by breathing warm, moist air from a hot shower, a sink filled with very hot water or a humidifier. Also, drink plenty of fluids to prevent mucus from getting too thick.

Hard candies can help soothe your throat and may help reduce coughing. They work as well as medicated lozenges.

Some people get relief with a prescription inhaler similar to what people with asthma use. Doctors most often prescribe inhalers that contain albuterol. Albuterol opens the airways that can become partly closed during a chest cold. For more persistent coughing, you might also ask your doctor about a corticosteroid inhaler.

What Can I Expect Looking to the Future?

Doctors prescribe antibiotics for chest colds less often today than in the past. Studies such as this one help all of us to continue our progress toward more appropriate antibiotic use.