A cough is a critical reflex action designed to promote clearing of the upper airways. The material being coughed up may be as a consequence of many conditions - from a lung or sinus infection to an accidentally inhaled foreign object (for example, food or small toy). A cough may also be a symptom of compromised lung function (for example, wheezing) or reflect rare conditions (for example, anatomical malformations).
All children will cough occasionally but recurrent cough, difficulty breathing with cough or coughing up purulent or bloody material warrant a thorough and timely evaluation. A "wet" or "mucousy" cough will sound different than a "dry" or "scratchy" cough or a "barky" ("sounds like a seal") cough. It may be helpful to record the cough prior to an appointment with a child's doctor since a "picture" may be worth a thousand words.
Most pulmonary specialists will categorize cough symptoms as "acute" - those lasting less than four weeks vs. "chronic" - those lasting longer than four weeks.
What are the common causes of acute cough in children?
Since children's cough may be associated with a broad array of situations, it is helpful to consider possible causes under various categories. These would include:
- The number one cause of cough in children would the common cold (URI - upper respiratory infection). Generally this cough is secondary to drainage of mucous down the back of the throat, thus stimulating the cough reflex center. Most children less than eight years of age cannot "cough up" this material efficiently. Generally their cough pushes the drainage from one area of the back of the throat to another. Children commonly will swallow the mucous after coughing and during sleep. Children have been known to cough with such force that they may vomit up previously swallowed mucoid material.
- Irritation and swelling of the vocal cord region caused by a viral infection may produce a characteristic "barky" cough (sounding similar to that of a seal). Such a viral infection is termed croup.
- A sinus infection is generally a complication of a URI and may be associated with consistent thick and purulent (green or yellow) nasal drainage either onto the facial region or down the back of the throat. This drainage will also stimulate the cough center as described above.
- Lower airway infections (i.e. those inside the chest cavity) include viral illnesses (pneumonia, bronchitis, etc.) or bacterial causes (pneumonia, pertussis whooping cough), etc.).
The amount of watery nasal drainage produced as a consequence of nasal allergy may be considerable. The material may commonly drain down the back of the throat ("post nasal drainage") and trigger the cough center in the rear of the throat.
Any object that does not pass from the back of the mouth into the esophagus runs the risk of aspiration into the windpipe (trachea). This is most common in young toddlers due to their infatuation with smaller objects and their intense oral fixation. Any object that can pass through the opening of a vertically oriented toilet paper cardboard tube is considered a risk object. Older children or adults who incompletely chew food prior to swallowing may also aspirate material. Effective emergency treatment of such a situation may be learned in CPR classes commonly taught by either the Red Cross or your local hospital.
Narrowing the functional diameter of the smaller airways make it difficult to breath (exhalation worse than inhalation) and can cause a characteristic sound during respiration. Wheezing is a consequence of two phenomena - narrowing the airway secondary to tightening of the muscles that wrap around this lung region, as well as thickening of the lining of the airway as a consequence of inflammation. In children the most common trigger to produce these reactions is the virus that causes the common cold (URI). Certain viruses (for example, respiratory syncytial virus ) are notorious in this regard. The environment (grasses, dust, mold) may also trigger such a reaction. In older children intense physical activity or cold air may also trigger a wheezing episode.
Gastroesophageal reflux disease (GERD)
Regurgitation of stomach contents and/or acid may trigger a reflex cough and should be considered when the more common causes of cough have been eliminated. This is more common in infants and young children. These young children and infants may not have obvious spitting up of liquids or solids during such episodes; however, they become very irritable during such events.
Benign motor tic
Children may occasionally have repetitive throat clearing as manifestation of a tic. They do not seem to be in any distress during these episodes and the child may stop them voluntarily and they do not occur during sleep. Parents will often describe such cough as "she has a tickle in her throat".
Various rare causes of cough need to be considered when the more obvious or routine mechanisms have been eliminated. A partial listing includes: cystic fibrosis, congenital heart disease, heart failure, congenital malformations of the airway, lungs or major blood vessels of the chest, etc.
What are the common causes of chronic cough in children?
Many of the causes (etiologies) of acute cough discussed above may also persist greater than four weeks and thus be classified as chronic cough. Two causes of acute cough which generally have a shorter than four week lifespan include: upper repsiratory infections (generally a maximum of 2 week duration) and croup (generally 4 to 6 day duration). Some studies have estimated that 5% to 7 % of preschoolers and 12 to 15 percent of older children may have chronic cough. Males are more likely to have chronic cough than female,s and chronic cough is more likely in underdeveloped countries than in those more affluent.
Causes of chronic cough (in addition to those listed above for acute cough) include:
- Irritation of the airways: pollution, primary or secondhand smoke, and an allergen may also produce persisting cough. Elimination or reduction of the offending irritant is therapeutic.
- Increase in cough receptor sensitivity: Some children seem to have a more sensitive response to irritants than their peers. The mechanism for this increase in cough receptor sensitivity is not well defined at this time. Possibilities under consideration include inflammation, erosion of the surface cell layer of the airway or a sensitization of the airway. The diagnosis may be explored in research centers using a cough-inducing irritant (capsaicin) as a quantifiable stimulant. Interpretation of such data is in the infancy stage.
- Habit cough: This cough has both a psychological and physical component. While often triggered by the common upper repsiratory infection, the duration of cough symptoms far exceeds the duration of the viral infection. Parents will describe a distinctive quality of cough: short, dry, single episodes that may mimic a benign motor tic (see above). Unlike a tic, the cough may be quite loud and disruptive to the classroom setting. The cough is commonly present during a medical evaluation but it does not characteristically interfere with play, sleep, talking, or eating. No specific diagnostic evaluation exists and habit cough is a diagnosis of exclusion. Counseling is generally an effective management technique.
- Otogenic cough: A minority of individuals have a branch of the nerve used in the cough reflex lining the ear canal. Irritation of the canal (Q-tips, ear wax [cerumen], etc.) may cause irritation of this nerve and thus induce a persisting and non-productive cough. While this is a relatively rare cause of children's cough, removal of the offending agent is curative.
How is the cause of childhood cough diagnosed?
As in most medical evaluations taking a thorough history and conducting a comprehensive physical examination generally leads to a narrow list of diagnostic possibilities. Laboratory studies, X-ray studies and specialized testing by allergists or pulmonary specialists may occasionally be necessary to establish or confirm the cause of childhood cough.
Issues to be evaluated while taking a history of childhood cough include:
- Duration and intensity of cough,
- Character of the cough (for example, the "bark" of croup),
- Events leading up to the cough (for example, possibility of foreign body aspiration),
- Events which affect cough (for example, physical activity produces increase in cough and shortness of breath in wheezing),
- Precipitating events associated with cough (for example, GERD symptoms associated with feeding),
- Progressive worsening of symptoms and development of fever (for example, pneumonia as complication of upper repsiratory infection),
- Environmental influences (for example, nasal allergy), and
- Possible emotional component (for example, benign motor tic).
Testing may include:
- Chest X-ray and/or sinus X-rays,
- Pulmonary function tests - determines the adequacy of lung inspiration and expiration effort and capability,
- Allergy testing,
- Nasal swabs for specific infectious agents (for example, respiratory syncytial virus, pertussis whooping cough),
- Specialized X-ray studies to help define anatomy (for example, barium swallow), and
- Endoscopy and bronchoscopy (insertion of a flexible device with camera to evaluate the upper airway.