Causes of Cough
There can be numerous causes of cough. Acute or short term cough usually lasts less than 3 weeks whereas chronic or persistent cough can last from 3 to 8 weeks. The various causes are discussed below:
I. Causes of acute or short-term cough
1. Acute viral or bacterial upper respiratory infection
Viral infections of the upper respiratory tract which include the common cold, viral laryngitis and influenza are the most common cause of cough. In such cases, cough is usually accompanied by fever, sore throat and runny nose. Cough can also occur due to bacterial infections in certain cases.
2. Inhalation of irritants or allergens
Acute exposure to dust, smoke, toxic fumes, mold, pollen & pet fur can cause inflammation of the upper respiratory tract and initiate coughing.
3. Acute rhinosinusitis
In acute rhinosinusitis, there is an inflammation and infection of the lining of the paranasal sinuses. This infection can cause mucus to collect at the back of the throat, which may make the throat itch. Some people might frequently cough to try to clear their throats, while others might experience uncontrollable coughing.
4. Pertussis or whooping cough
Pertussis or whooping cough may cause violent coughing led by a gasp for air. Pertussis is caused by a bacteria called Bordetella pertussis that affects the respiratory tract.
5. Lower respiratory tract infections
These are more severe viral and bacterial infections which can affect the airways in case of bronchitis and even the lungs in case of pneumonia. They usually cause a deep, persistent cough along with fever.
II. Causes of chronic or persistent cough
The reason behind a chronic cough is more difficult to diagnose. It needs diagnosis from a cough specialist or a pulmonologist. Possible causes of chronic cough include:
1. Upper airway cough syndrome
Upper airway cough syndrome is a chronic post-nasal drip, which tends to irritate the upper airway, inducing cough.
2. Hay fever or allergic rhinitis
Allergic rhinitis is an inflammation of the nasal mucosa, which is secondary to an allergic irritation occurring due to environmental factors. This results in increased mucus secretion. The mucus may also gather in the throat, causing post-nasal drip. This, in turn, may irritate the airways and stimulate a cough. It is usually associated with dry cough, sneezing and runny nose.
3. Chronic sinusitis
After a bacterial infection, your sinus and nasal mucosa may become irritated and inflamed, resulting in cold-like symptoms and cough over time.
4. Chronic bronchitis
Excessive mucus plugging in the airways causes a cough that lasts more than 3 months. Chronic bronchitis is not always of infectious origin but may be caused by bacterial infections in the past. Smoking is also an important risk factor of chronic bronchitis, and thus, a cause of cough.
5. Post-infectious cough
While recovering from an infection, the cough receptors become hyperresponsive, thereby inducing cough.
6. Gastroesophageal reflux disease (GERD)
In GERD, acidic contents from the stomach enter into the throat. This causes the receptors in the throat to get irritated, causing cough. Cough caused due to GERD worsens on lying down because on lying down the stomach contents travel back to the throat and cause cough.
7. Asthma
In asthma, the body's immune system becomes hyper-responsive to external factors. This may cause inflammation, bronchial hyperreactivity & intermittent airflow obstruction with constriction of the airways, thereby inducing cough.
8. Chronic obstructive pulmonary disease (COPD)
It is a chronic inflammatory lung disease that causes obstructed airflow from the lungs and is usually associated with smoking. A cough caused by smoking is almost chronic in nature with a distinctive sound. It’s often called a smoker’s cough.
9. Congestive heart failure (CHF)
In CHF, the heart’s ability to pump blood reduces. This results in buildup of fluid in the lung, causing cough.
10. Intolerance to angiotensin-converting enzyme (ACE) inhibitor medicine
A dry cough is one of the most bothersome side effects of ACE inhibitors taken by people for hypertension.
11. Obstructive sleep apnea
In obstructive sleep apnea, the airways get partially or completely blocked for a short period of time during your sleep. This raises airway resistance, thereby causing chest and diaphragm spasms, resulting in cough.
12. Throat disorders
Diseases such as croup in children, cause a distinctive barking cough and a harsh sound called stridor when the child breathes in.
13. Psychosomatic cough
This type of cough has psychological causes such as anxiety, stress and depression and may have been adapted with habit rather than any disease condition.
III. Other less common causes of cough
1. A foreign body
Accidently, food or other objects can go down the windpipe instead of the food pipe causing cough.
2. Tuberculosis (TB)
Symptoms of TB are usually coughing for three or more weeks along with coughing up blood or mucus, chest pain, or pain with breathing or coughing.
3. Lung cancer
Cancer starts when cells in the lung begin to grow out of control. It is mostly associated with chronic smokers.
4. Cystic fibrosis
This is a genetic disorder that affects the lungs and causes chronic cough.
5. Bronchiectasis
This is a condition in which airways of the lungs are permanently damaged and widened leading to a buildup of extra mucus.
6. Pulmonary embolism
In pulmonary embolism, a blood clot or embolus travels, usually from the legs, to the lungs causing sudden shortness of breath along with a lingering dry cough.
7. Pneumothorax
A pneumothorax or a collapsed lung occurs when air leaks into the space between the lung and the chest wall. It can be spontaneous or due to some chest injury, certain medical procedures, or underlying lung disease. Signs of a collapsed lung include sudden chest pain, dry cough and shortness of breath.