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What Causes a Cough

Cough is a rapid exhalation through a partially closed glottis. In simpler terms one breathes out hard while narrowing the airway so as to make the air movement faster. Its function is to clear secretions and foreign bodies from the airway. It can be voluntary but most often is involuntary.
Cough is a normal daily activity. However, we are usually unaware of the occasional cough that occurs during periods of wellness. In contrast, we are usually very aware of the frequent cough which is associated with many illnesses.

Cough is associated with both upper respiratory illnesses including the common cold, rhinitis, sinusitis, and pharyngitis, and lower respiratory illnesses including laryngotracheitis, tracheitis, bronchitis, bronchiolitis, asthma, and pneumonia. Rarely, cough is psychogenic (imagined need to cough), or as a side effect of medications, or even from heart failure.

Cough does serve the beneficial function of clearing the airways; however, often, the frequency and severity of the cough are far in excess of what is necessary. Severe cough can result in interrupted sleep, throat pain, vomiting/reflux (medically termed “post-tussive emesis”), chest wall and abdominal discomfort, and even rib fracture in adults. Making matters worse is the fact that severe cough is self perpetuating. It is the irritation of the airways which causes a cough, but the cough itself further irritates the airways, resulting in a vicious cycle.

Treatment of a cough should be undertaken with the goal of decreasing the cough to some degree. Frequently parents feel a cough medication is not working because the child still has a cough. No cough medication is effective enough to result in the cessation of all coughing. Nor would the cessation of all coughing be desirable, especially during illnesses wherein increased mucus finds its way into the airways.

Treatment of the cough may be with any one or several classes of agents. Cough suppressants (dextromethorphan or prescription opiates (codeine, hydrocodone)) act on the brain to decrease the perception of airway irritation. Expectorants (guaifenesin) loosen mucus, making it easier to expel. Antihistamines and decongestants may help cough by decreasing or drying mucus and keeping it from dripping (post nasal drip) from the upper airway to the lower airway. Topical anesthetics (menthol and others) decrease cough by blocking the sensation of airway irritation. If there is wheezing, or reactivity of the airways as with bronchitis, bronchiolitis, asthma, and cough variant asthma, bronchodilators (albuterol and others) should be the mainstay of therapy.

When does a cough need to be evaluated?

If a cough is associated with any degree of breathing difficulty, your child needs to be seen right away. This may include in emergency room treatment if the symptoms begin after office hours. If there is fever or wheezing with the cough, you should make an appointment for your child to be seen as promptly as possible. (Exceptions are in an infant less than 3 months of age, or if the wheezing follows a choking or gagging spell–under these circumstances immediate evaluation is necessary.)

If the cough is not severe and seems associated with cold symptoms you can use over-the-counter medications without formal evaluation, provided the cough continues to improve. If the cough persists for more than two weeks, your child should be evaluated.

If your child does not fall into any of these categories, you should call your child’s physician for advice on how to proceed.