If you got a pesky cough and it hasn`t gone away in a week, you shouldn`t fret as a new study has found that the average cough lasts 18 days.

The problem is that people may believe that acute coughs - otherwise known as acute bronchitis-last about 10 days shorter than that, leading researchers to believe that many of them unnecessarily ask their doctor for antibiotics.

The Centers for Disease Control and Prevention estimates that acute cough illness makes up two to three percent of doctor visits, and more than half of them leave with an antibiotic prescription.

"There is a mismatch in what people believe and reality," CBS News quoted Dr. Mark Ebell, associate professor of epidemiology in the UGA College of Public Health, as saying.

"If someone gets acute bronchitis and isn`t better after four to five days, they may think they need to see a doctor and get an antibiotic. And when the first one doesn`t work, they come back four or five days later for another," he said.

The study looked at 19 observational studies that had between 23 and 1,230 patients. The studies took place in the US, Europe, Russia and Kenya.

From the data, it was determined that acute cough illness lasts 17.8 days on average.

The study is published in the journal Annals of Family Medicine.