Asthma, postnasal drip and gastroesophageal reflux disease are all causes of chronic cough in adults, according to Mayo Clinic. Infections, chronic bronchitis and certain drugs used to control blood pressure are additional causes. Although less common, conditions such as cystic fibrosis, chronic obstructive pulmonary disease, lung cancer and sarcoidosis also cause chronic coughing. Rather than always having a singular cause, chronic coughs may result from multiple causes.
The chronic cough associated with asthma may be affected by the seasons or appear after an infection of the upper respiratory tract, notes Mayo Clinic. Coughing is the main symptom of cough-variant asthma. Coughing in asthmatic patients may also worsen after exposure to fragrances, chemicals or cold air.
Postnasal drip is a major cause of coughing, suggests Mayo Clinic. The cough results when the sinuses or nose produce excess mucus that drips down the back of the throat, triggering the body’s normal reflex to cough in order to dispel secretions from the body.
Gastroesophageal reflux disease, or GERD, causes acid to flow back into the esophagus, which is the tube connecting the throat and the stomach, reports Mayo Clinic. When this happens, the esophagus becomes irritated, which leads to chronic cough.
Asthma, postnasal drip and GERD, either on their own or in combination with one another, cause 90 percent of chronic cough cases, notes Mayo Clinic.