Coughing is a natural protective mechanism to enable our body to prevent aspiration (breathing in) of mucus (phlegm) or foreign materials into the airways and lungs. Occasional cough to clear the throat of mucus or foreign materials is normal. However, when cough becomes present for persistent periods, it may indicate an underlying illness.
Cough can be productive or non-productive. Productive cough is a type of cough that produces secretions or phlegm. The phlegm can be thick (sticky) or thin, and it can be clear, yellowish, greenish, or sometimes bloody. Non-productive cough or dry cough is a type of cough that does not produce phlegm. Differentiation of these two types of cough is important because it can give clues as to the cause of cough.
Causes of productive cough
Although this is not a hard and fast rule, most productive coughs are usually due to:
- Infection: Infection of the respiratory tract from the upper airways (as in the case of Upper Respiratory Tract Infection) to the lungs (as in the case of Pneumonia) can lead to production of phlegm. The phlegm can be whitish to yellowish, depending on the duration and severity of the infection.
- Postnasal drip: Postnasal drip happens when the discharge from the sinuses drains to the back of the throat, causing the need to clear the throat frequently. Thin and clear secretions usually characterize this unless a sinus infection is present.
- Acid reflux: Acid reflux happens when the acid from the stomach refluxes upward and finds its way to the throat and to the airways. This causes irritation of the throat, leading to frequent coughing.
- COPD: Chronic obstructive pulmonary disease (emphysema or chronic bronchitis) is a long-standing disease of the airways that happens when the airways are damaged by heavy smoking. This is characterized by shortness of breath associated with frequent production of phlegm.
- Smoking: Smoking can irritate and damage the airways, leading to production of copious phlegm.
Causes of dry cough
Most dry coughs are caused by:
- Viral illness: Most viral illnesses that are associated with colds resolve spontaneously, but the cough associated with it usually remains for a few days even if the viral illness has resolved.
- Allergy and Asthma: Bronchial asthma and allergy to certain materials can cause hyper-reactive airways that narrow down easily, causing coughing and wheezing.
- Irritation: Dust, fumes, smoke, and other materials can irritate the airways and lead to coughing.
- Medicines: Some medications like the ACE inhibitors for hypertension can have cough as a side effect.
- Foreign body: Foreign bodies in the airway (which are particularly common in children) can obstruct the airways and cause repeated bouts of coughing in an effort of the body to expel the foreign material.
When to see a doctor
Some coughs, especially the non-productive ones, can resolve spontaneously even without intervention. However, some coughs require a visit to the physician for proper assessment and treatment. In general, consult should be done if the following symptoms are present:
- Productive cough—any productive cough warrants investigation
- Difficulty of breathing
- Blood in the phlegm
- Cough for several days after a history of choking
- Cough for more than 2 weeks
- Cough associated with unintentional weight loss
- Cough that interrupts daily activities
- Is younger than 4 months’ old
- Is having trouble breathing, has noisy breathing, or is breathing very fast
- Gets a cough after he or she choked on food or another object, even if he or she choked on the object days or weeks ago
- Is coughing up blood, or yellow or green mucus
- Refuses to drink anything for a long time
- Has a fever and is not acting like him- or herself
- Is coughing so hard that he or she vomits
To diagnose the cause of a cough, the doctor will do a thorough history of the duration, character, and triggering factors of the cough. A comprehensive physical examination will also be done which includes a meticulous auscultation of the chest. After that, a doctor might request for additional tests depending on his findings. Some of these tests are:
- Chest X-ray: to get an image of the lungs and related structures
- Sputum exam: to analyze the phlegm that you cough up and detect the microorganisms in it that might have caused the infection
- Spirometry: involves breathing into a tube to test the capacity and function of the lungs
- Skin tests: to detect possible causes of allergy
- Chest CT scan: to get a better picture of the lungs
- Bronchoscopy: involves insertion of a scope through the nose and into the airways to inspect for damages or foreign bodies in the airways
- Tests to evaluate for acid reflux if history suggests it (upper GI endoscopy)
Treatment of cough depends on the underlying cause of the cough.
- Respiratory infections are treated with at least 7-10 days of antibiotics
- Postnasal drip is treated with steroid nasal sprays that decrease nasal discharge
- Acid reflux is treated with medications such as antacids and others
- COPD is treated with bronchodilators that open up the airways and steroids that decrease the inflammation of the airways
- Asthma and allergies are treated with antihistamines (medications for allergy), bronchodilators and steroids.
- Foreign bodies are removed through bronchoscopy.
Special considerations for children — Any child younger than age 6 should NOT be given any cold medicines, as they are not considered safe for young children.
Over-the-counter pain medications like acetaminophen and ibuprofen are fine. However, for children, the dosage of these medications is dependent on weight, so a doctor’s advice might be beneficial. Aspirin, a common pain medication, should not be given to children because it can cause Reye’s syndrome. Reye’s syndrome is a rare but potentially fatal condition that is characterized by rashes, seizures and confusion due to the swelling of the brain and the liver.
Other supportive treatments that can help alleviate cough are:
- Room humidifier: to add moisture in the air that you breathe
- Cough syrups: to make it easier for you to cough out the phlegm or to suppress
- Increase water intake: to dilute the phlegm and make it easier to cough out
- Avoidance of irritants like dust, fumes, or smoke by wearing a mask
- Avoidance of allergens
- Quitting smoking