Don't waste your money on over-the-counter cough syrup -- doctor's orders. Despite the plethora of cough remedies on the market, new guidelines from the American College of Chest Physicians say cough expectorants or suppressants, including cough syrups and cough drops, do not treat the underlying cause of the cough.

"Cough is the number one reason why patients seek medical attention. Although an occasional cough is normal, excessive coughing or coughing that produces blood, or thick, discolored mucus is abnormal," said Chair of the guidelines Dr. Richard S. Irwin of the University of Massachusetts Medical School, Worcester.

"The new ACCP guidelines define how physicians should diagnose and manage cough associated with everything from the common cold to chronic lung conditions. The guidelines also are the most comprehensive evidence-based recommendations for treating cough in children."

The new guidelines recommend that for adults with acute cough or upper airway cough syndrome (previously named postnasal drip syndrome), an older variety antihistamine with a decongestant is the preferred therapy. Cough medicine, the guidelines say, won't do any good.

"There is no clinical evidence that over-the-counter cough expectorants or suppressants actually relieve cough," Irwin said. "There is considerable evidence that older type antihistamines help to reduce cough, so, unless there are contraindications to using these medicines, why not take something that has been proven to work?"

Children's cough syrup also has little apparent value. Although the guidelines address all types of pediatric cough, they make a strong recommendation against the use of over-the-counter cough and cold medications for children age 14 years and younger.

"Cough is very common in children. However, cough and cold medicines are not useful in children and can actually be harmful," said Irwin. "In most cases, a cough that is unrelated to chronic lung conditions, environmental influences, or other specific factors, will resolve on its own."

Of the estimated 829 million visits to office-based physicians in the United States, approximately 29.5 million are for cough.

The guidelines strongly recommend that adults up to 65 years old receive a new adult vaccine for whooping cough (pertussis), a highly contagious type of subacute cough that gets its name from the loud "whooping" noise patients make when they cough. Because antibiotics are only effective early on in the infection, preventing whooping cough with a vaccine is the only way to eventually eliminate the disease.

Once whooping cough takes hold, the coughing patient is at risk of serious complications of coughing, such as vomiting, breaking ribs, passing out, and passing the infection on to others.

"Most of us think of whooping cough as a childhood disease, yet 28 percent of whooping cough cases in the United States is in adults," Irwin said. "Although most of us were vaccinated against whooping cough when we were children, the older vaccine only gives protection for less than 10 years. Because the older vaccine caused serious side effects when given to older children and adults, it was only given to children. Fortunately, there is a now a new safe and effective whooping cough vaccine that can prevent adults from contracting this disease."

Additional recommendations address the most common causes of chronic cough, including upper airway cough syndrome (previously named postnasal drip syndrome), asthma, and gastroesophageal reflux disease (GERD). Chronic cough also may be a result of smoking or taking angiotensin-converting enzyme (ACE) inhibitors.

An acute cough is generally caused by a "common cold" -- a subacute cough can linger after a cold or may persist due to a respiratory tract infection, such as whooping cough or other postinfectious cough.