Cough is common, and can linger, especially during the allergy season. But does cough equal allergy?
A cough can be an annoying, embarrassing symptom, or an important clue leading to rapid diagnosis and effective treatment. It is one of the most common reasons to see a lung specialist, accounting for more than one third of new patient visits in many practices. There is an abundance of confusing medical literature available, most of it on the internet; a recent search found more than 300 articles related to chronic cough published so far this year, and that’s only the tip of the iceberg.
Coughing itself is remarkably effective. Acute cough is our primary defense mechanisms to protect the airways and lungs from unwanted invaders, such as aspirated food or secretions laden with bacteria or acid from the stomach. Receptors line the major airways to trigger an acute cough, which can create flow rates approaching the speed of sound! This rapid air flow creates shearing forces that move secretions up and out, but unwanted effects, such as rib fractures, sprained chest muscles and even syncope (brief loss of consciousness) can result.
What makes a cough chronic? The accepted time scale is three weeks without an obvious precipitating cause. There are many clues to the cause of a cough which your physician can review with you. Generally a carefully taken health history and physical exam will identify many major concerns, such as asthma or allergy, exposure to inhaled toxins, or medicines known to cause cough. Smoking is of course an irritant; it inhibits normal mucus clearance mechanisms, and most long term smokers have a chronic cough, though some are not bothered by it. The timing, nature and history of the cough are important to review, along with associated respiratory symptoms and findings on physical exam, such as abnormal breath sounds. Chest x-ray and tests of lung function are helpful in the detection of unexpected or subtle abnormalities, such as airflow obstruction indicating asthma or COPD. “Post infectious” cough can follow respiratory infections, either minor or major, and can last for months. A state of airway hyper-responsiveness develops even though the infection itself has resolved. Frequently anti-inflammatory medicines, such as those used for asthma, are given to bring the airway back to normal. Acid reflux is another occult cause for chronic cough, as is allergic post-nasal drainage. Frequently these conditions produce minimal symptoms except for the cough. Surprisingly the majority of well established coughs have more than one cause as their basis. All must be treated, or resolution does not occur.
In most cases, rare or life threatening causes are easily ruled out and common causes, such as asthma, allergic drainage and acid reflux, are diagnosed and treated effectively. Resolution and patient satisfaction depend heavily on a systematic evaluation and adequate length of therapy, thus a good working relationship with your Physician is key.