A cough is a sudden and often repetitively occurring reflex which helps to clear the large breathing passages from secretions, irritants, foreign particles and microbes. The cough reflex consists of three phases: an inhalation, a forced exhalation against a closed glottis, and a violent release of air from the lungs following opening of the glottis, usually accompanied by a distinctive sound. Coughing can happen voluntarily as well as involuntarily.
Frequent coughing usually indicates the presence of a disease. Many viruses and bacteria benefit evolutionarily by causing the host to cough, which helps to spread the disease to new hosts. Most of the time, coughing is caused by a respiratory tract infection but can be triggered by choking, smoking, air pollution, asthma, gastroesophageal reflux disease, post-nasal drip, chronic bronchitis, lung tumors, heart failure and medications such as ACE inhibitors.
Treatment should target the cause; for example, smoking cessation or discontinuing ACE inhibitors. Some people may be worried about serious illnesses, and reassurance may suffice. Cough suppressants such as codeine or dextromethorphan are frequently prescribed, but have been demonstrated to have little effect. Other treatment options may target airway inflammation or may promote mucus expectoration. As it is a natural protective reflex, suppressing the cough reflex might have deleterious effects, especially if the cough is productive.
A cough can be the result of a respiratory tract infection such as the common cold, pneumonia, pertussis, or tuberculosis. In the vast majority of cases, acute coughs, i.e. coughs shorter than 3 weeks, are due to the common cold. In people with a normal chest X-ray, tuberculosis is a rare finding. Pertussis is increasingly being recognised as a cause of troublesome coughing in adults.
After a viral infection has cleared, the person may be left with a postinfectious cough. This typically is a dry, non-productive cough that produces no phlegm. Symptoms may include a tightness in the chest, and a tickle in the lungs. This cough may often persist for weeks after an illness. The cause of the cough may be inflammation similar to that observed in repetitive stress disorders such as carpal tunnel.
The repetition of coughing produces inflammation which produces discomfort, which in turn produces more coughing creating a closed loop. Postinfectious cough typically does not respond to conventional cough treatments. Treatment consists of any anti-inflammatory medicine to treat the inflammation, and a cough suppressant to reduce frequency of the cough until inflammation clears. Inflammation may increase sensitivity to other existing issues such as allergies, and treatment of other causes of coughs (such as use of an air purifier or allergy medicines) may help speed recovery. A bronchodilator, which helps open up the airways, may also help treat this type of cough.
An acute cough generally accompanies a health condition of sudden onset such as an upper respiratory INFECTION (colds, ﬂu, BRONCHITIS, PNEUMONIA), SINUSITIS (sinus infection), and PHARYNGITIS. An acute cough can be either productive or nonproductive though is usually productive because the IMMUNE SYSTEM increases mucus production to help rid the body of the PATHOGEN. ANTIBIOTIC MEDICATIONS are necessary to treat infections that are bacterial. Viral infections typically run their course and do not require medications except to relieve symptoms. In infections, coughs are often productive, bringing up dead cells and other debris that the body needs to clear from the airways. POSTNASAL DRIP, which irritates the pharynx, is a key cause of coughs related to upper respiratory infections.
COVERING A COUGH
Coughs can spread infections both through droplets in the air and through hand contact.
Health experts recommend coughing into the crook of the arm rather covering the mouth with the hands. Frequent HAND WASHING also helps reduce the spread of pathogens.
A chronic cough may signal an underlying health condition or may exist as a response to continued irritation, most commonly cigarette smoking. Other common causes of chronic cough include
• GASTROESOPHAGEAL REFLUX DISORDER (GERD), in which gastric acid from the stomach enters and irritates the throat
• Asthma and seasonal allergies
• Chronic sinusitis
• Pulmonary diseases such as chronic bronchitis, COPD, and BRONCHIECTASIS
Generally, eliminating the underlying cause of chronic cough also eliminates the cough. A signiﬁcant risk with smoker’s cough is that it develops so gradually the smoker may not realize how often he or she coughs. The cough may exist as a response to the irritation of smoking or may signal a serious health condition such as lung disease or
throat or lung cancer. A doctor should evaluate chronic cough in smokers on a regular basis to monitor for more signiﬁcant health problems.
SMOKING CESSATION may end the cough; cough that continues longer than six months beyond smoking cessation may indicate another health condition and requires a doctor’s assessment.
Treatment focuses first on eliminating any underlying reasons for cough. Antibiotic medications are helpful only when there is a bacterial infection. The most effective cough suppressant medications are those which contain DEXTROMETHORPHAN, benzonatate, or NARCOTICS such as codeine and hydrocodone. Products containing benzonatate (a non-narcotic) or narcotics require a doctor’s prescription and are not generally appropriate for chronic cough. Products containing dextromethorphan are numerous and available over the counter; extended-release products can provide
relief for 10 to 12 hours per DOSE.
Expectorants help thin mucus and secretions so the coughing mechanism can more easily bring them out of the airways. Doctors do not agree on whether expectorants are truly helpful, and there are few clinical research studies that have investigated their effectiveness. The most common expectorant in cough products sold in the United States is guaifenesin. Manufacturers recommend drinking plenty of water when taking products
containing guaifenesin; some health experts believe increased water intake alone is adequate to thin mucus.
Most cough products, both prescription and over the counter, combine ingredients, so it is
important to read product labels carefully. Products may include a cough suppressant and an expectorant as well as a decongestant, an antihistamine, and other substances.
Maintaining adequate moisture in the air (as with a cool humidiﬁer), drinking plenty of liquids, and avoiding substances that irritate the throat and airways are effective nonmedication methods for managing cough, especially chronic cough.