Persistent Dry Cough at Home: Possible Causes and Solutions - Otolaryngology

Dr. Ye Dawei reply Otolaryngology

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Subject: Possible Relationships
Coughing can be related to various factors.
Just as we fear leaks when building a house, doctors fear misdiagnosing a cough.

Viral Infections – Viral Bronchitis
Coughing occurs in our bodies due to the presence of "cough receptors" in the throat, trachea, bronchi, sinuses, and ears.
When these areas are stimulated or inflamed, they can produce secretions that trigger a cough reflex.
Similar to fever, in addition to administering antipyretics to soothe patients (or their families), it is crucial not to overlook identifying the underlying causes of symptoms (fever, cough).
Generally, the common cold (caused by rhinoviruses, adenoviruses, respiratory syncytial viruses, parainfluenza viruses, coronaviruses, etc.) primarily presents with nasal symptoms (runny nose, nasal congestion) and rarely causes coughing.
Sometimes, coughing is actually due to post-nasal drip irritating the "cough receptors." The most common cause of coughing is "viral bronchitis." As mentioned earlier, the common cold rarely results in a cough; if a cough persists for several days, it should be diagnosed as bronchitis, with the causative viruses being similar to those of the common cold.
The bronchi are part of the respiratory tract, and viral infections do not selectively target just the bronchi, so in addition to coughing, patients often exhibit conjunctivitis, runny nose, sore throat, hoarseness, fever, or fatigue as systemic symptoms.
Bacterial Infections – Bacterial Bronchitis and Sinusitis
Bacterial bronchitis is less common but should not be overlooked, as it could delay the use of antibiotics.
For example, during the recent flu outbreak, Hsinchu Hospital reported multiple cases of cough patients infected with "Mycoplasma." Focusing solely on diagnosing influenza viruses can easily lead to severe pneumonia complications.
The common cold typically lasts less than a week, while bronchitis or pneumonia can extend to two to three weeks.
If a patient has a persistent cough and high fever, in addition to considering asthma or allergic conditions and foreign body aspiration, one must be vigilant about Mycoplasma infection.
Due to the nature of this infection, doctors often find no specific findings upon auscultation, but X-rays frequently reveal extensive pneumonia or even pleural effusion.
The inconsistency between X-ray findings and clinical auscultation often leads to diagnostic delays.
Mycoplasma antibodies are a type of cold agglutinin that can show agglutination at low temperatures (4 °C), serving as a diagnostic basis.
Mycoplasma lacks a cell wall, so common antibiotics like cephalosporins or penicillin are ineffective; the standard treatment is erythromycin for two weeks.
Another less common cause of bacterial bronchitis is the Bordetella pertussis bacterium.
Recent reports of antibiotic misuse in the media are related to the use of erythromycin to prevent neonatal whooping cough, which has been linked to causing pyloric stenosis in infants—though this is a separate issue.
Allergic Conditions – Bronchial Allergy (Asthma) and Cough Variant Asthma
For a patient with a cough lasting more than two weeks without improvement, it should not merely be attributed to an unresolved cold.
At this point, one should be alert to the previously mentioned bacterial infections, lobar collapse (most commonly due to foreign body aspiration), and asthma.
The vast majority of post-cold coughs are caused by asthma, and many children with asthma or sinusitis may only present with a cough.
Therefore, differential diagnosis of cough should not solely focus on the presence of redness or swelling in the throat (which is not significantly related to coughing); it is essential to examine the nasal passages and auscultate the chest.
This is to avoid missing a sinusitis diagnosis that requires timely antibiotic treatment or misclassifying asthma as a cold or heart disease.
Asthma symptoms can vary widely, with each patient presenting differently, and they can easily be confused with common diseases in various specialties.
Coughing is often attributed to post-nasal drip or unresolved colds; palpitations and chest pain are considered heart disease; shortness of breath when climbing stairs is attributed to obesity or lack of exercise.
Just as otolaryngologists are often the first line of clinicians to diagnose HIV patients, they also frequently diagnose asthma.
Patients often visit the clinic for a cold, and if they have a persistent cough along with other allergic symptoms such as runny nose, sneezing, and itchy eyes, one should suspect asthma.
There is also a condition known as cough variant asthma (CVA), where chronic cough is the only symptom, with no history of asthma or respiratory distress, and normal lung function tests, but the airways are abnormally sensitive, and cough resolves after using bronchodilators.

You may wonder why an otolaryngologist discusses asthma; the current specialization system is often criticized for being overly detailed.
While this allows for more precise diagnoses and treatments for specific diseases, it has led to peculiar phenomena where specialists may overlook related conditions.
For instance, a patient with dizziness may be diagnosed with Meniere's disease in an ENT clinic, but when seen in a neurology clinic, they may be labeled as having cerebral asthenia.
Similarly, a cough patient in an ENT clinic may be diagnosed with post-nasal drip, while a visit to an internist may lead to a diagnosis of asthma.
I believe that primary care physicians should pay more attention to diseases outside their specialty.

In summary, unless the second or third categories of bacterial secondary infections or asthma are involved, most bronchitis cases can resolve naturally.
The first category, viral bronchitis (the most common cause of coughing), has a defined course, often transitioning from a dry cough to a productive cough with phlegm after a few days.
Patients may mistakenly believe that their condition worsens with medication as they begin to cough up more phlegm.
Cough Treatment Medications
In outpatient settings, medications related to cough treatment can generally be categorized into three main types: antitussives, expectorants, and throat soothers.
Commonly prescribed antitussives include dextromethorphan and codeine (which contains narcotic components).
Their mechanism of action suppresses the cough reflex in the central nervous system and is primarily used for early dry cough or non-productive cough patients.
Expectorants work by thinning secretions to facilitate the expulsion of mucus; doctors often recommend patients drink plenty of water and inhale steam to achieve expectorant effects.
Over-the-counter throat soothers include honey, licorice, glycerin, citric acid, and loquat syrup, which can alleviate discomfort in the throat.
Theoretically, productive coughs should not be suppressed with strong antitussives, as this can lead to retained secretions in the lower respiratory tract, especially in children under two years old, to avoid potential harm to the trachea or lung function.

In conclusion, when facing a cough, it is crucial to be aware of the underlying causes rather than simply suppressing the cough.
Most coughs should resolve naturally, and for patients with persistent coughs, it is essential to remain vigilant and rule out the potential causes mentioned above.
Dr.
Yeh Da-Wei, Director of the ENT Department, Hsinchu Hospital

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Reply Date: 2009/12/23