What is a cough?
A cough is a sudden, and often repetitively occurring, protective reflex which helps to clear the large breathing passages from fluids, irritants, foreign particles and microbes. The cough reflex consists of three phases: an inhalation, a forced exhalation against a closed glottis, and a violent release of air from the lungs following opening of the glottis, usually accompanied by a distinctive sound.
Frequent coughing usually indicates the presence of a disease. Many viruses and bacteria benefit, from an evolutionary perspective, by causing the host to cough, which helps to spread the disease to new hosts. Most of the time, irregular coughing is caused by a respiratory tract infection but can also be triggered by choking, smoking, air pollution, asthma, gastroesophageal reflux disease, post-nasal drip, chronic bronchitis, lung tumors, heart failure and medications such as ACE inhibitors.
Treatment should target the cause; for example, smoking cessation or discontinuing ACE inhibitors. Cough suppressants such as codeine or dextromethorphan are frequently prescribed, but have been demonstrated to have little effect. Other treatment options may target airway inflammation or may promote mucus expectoration. As it is a natural protective reflex, suppressing the cough reflex might have damaging effects, especially if the cough is productive.
What causes a cough?
A cough can be caused by several conditions, both temporary and permanent.
Clearing the throat
Coughing is a standard way of clearing your throat. When your airways become clogged with mucus or foreign particles such as smoke or dust, a cough is a reflex reaction that attempts to clear the particles and make breathing easier.
Usually, this type of coughing is relatively infrequent, but coughing will increase with exposure to irritants such as smoke.
Viruses and bacteria
The most common cause of a cough is a respiratory tract infection, such as a cold or flu.
Respiratory tract infections are usually caused by a virus and may last from a few days to a week. Infections caused by the flu may take a little longer to clear up and can sometimes require antibiotics.
Smoking is a common cause of coughing. A cough caused by smoking is almost always a chronic cough with a distinctive sound. It’s often known as a smoker’s cough.
A common cause of coughing in young children is asthma. Typically, asthmatic coughing involves wheezing, making it easy to identify.
Asthma exacerbations should receive treatment using an inhaler. It’s possible for children to grow out of asthma as they get older.
Some medications will cause coughing, although this is generally a rare side effect. Angiotensin-converting enzyme (ACE) inhibitors, commonly used to treat high blood pressure and heart conditions, can cause coughing.
Two of the more common ones are:
- Zestril (lisinopril)
- Vasotec (enalapril)
The coughing stops when the medication is discontinued.
Other conditions that may cause a cough include:
- damage to the vocal cords
- postnasal drip
- bacterial infections such as pneumonia, whooping cough, and croup
- serious conditions such as pulmonary embolism and heart failure
Another common condition that can cause a chronic cough is gastroesophageal reflux disease (GERD). In this condition, stomach contents flow back into the esophagus. This backflow stimulates a reflex in the trachea, causing the person to cough.
The majority of coughs are caused by viruses and clear up without treatment.
Causes of acute (short-term) cough
In most cases, the infection is in the upper respiratory tract and affects the throat, this is known as a URTI or URI (upper respiratory tract infection). Examples include:
- common cold
If it is an LRTI (lower respiratory tract infection), the lungs are infected, and/or the airways lower down from the windpipe. Examples include:
An acute cough can also be caused by hay fever.
When is coughing an emergency?
Most coughs will clear up, or at least significantly improve, within two weeks. If you have a cough that hasn’t improved in this amount of time, see a doctor, as it may be a symptom of a more serious problem.
If additional symptoms develop, contact your doctor as soon as possible. Symptoms to watch out for include:
- chest pains
Coughing up blood or having difficulty breathing requires immediate emergency medical attention.
If a doctor decides that a cough is caused by the common cold or flu, the general advice will be to rest, drink plenty of fluids, and let it run its course. In the majority of cases, such coughs clear up after 1–2 weeks.
A cough caused by a viral infection that persists for more than a couple of weeks will probably require medical attention.
The doctor may order some diagnostic tests, such as a chest X-ray; a sample of phlegm may be sent to a laboratory for analysis to determine what is causing the infection.
The patient may be asked to breathe in and out of a tube attached to a machine; this helps the doctor determine whether the airways have an obstruction (this test is called spirometry), which is common in asthma or emphysema.
If asthma is diagnosed, the patient may be prescribed asthma medication.
Sometimes, a doctor might refer the patient to a lung or ear, nose, and throat (ENT) specialist.
How is a cough treated?
Coughs can be treated in a variety of ways, depending on the cause. For healthy adults, most treatments will involve self-care.
According to the National Health Service (NHS), United Kingdom, a homemade remedy with honey and lemon is as good, if not better than most over-the-counter (OTC) products sold in pharmacies.
Treatments are mostly aimed at making the patient feel a little bit better but generally do not decrease the length of the cough.
Honey — it coats the throat, resulting in less irritation and possibly less coughing. Honey is a demulcent (something that soothes).
Cough medications — some may help associated symptoms, such as fever or a stuffy nose. However, there is no compelling evidence that cough medicines are effective in making the cough go away faster. A variety of cough medicine is available for purchase online.
For small children, it is a good idea to talk to a doctor before giving OTC cough medicine. Some ingredients in cough medicines, such as codeine, can be dangerous for small children. There is no evidence that cough medicines help children, and they can actually be dangerous due to the side effects.
Cough suppressants — these suppress the cough reflex and are generally only prescribed for a dry cough. Examples include pholcodine, dextromethorphan, and antihistamines.
Expectorants — these help bring up mucus and other material from the trachea, bronchi, and lungs. An example is guaifenesin (guaiphenesin), which thins the mucus and also lubricates the irritated respiratory tract, helping to drain the airways. Cough expectorants are available to purchase over-the-counter or online.
Typically, medical care will involve your doctor looking down your throat, listening to your cough, and asking about any other symptoms.
If your cough is likely due to bacteria, your doctor will prescribe oral antibiotics. You’ll usually need to take the medication for a week to fully cure the cough. They may also prescribe either expectorant cough syrups or cough suppressants that contain codeine.
If your doctor can’t find a cause for your cough, they may order additional tests. This could include:
- a chest X-ray to assess whether your lungs are clear
- blood and skin tests if they suspect an allergic response
- phlegm or mucus analysis for signs of bacteria or tuberculosis
It’s very rare for a cough to be the only symptom of heart problems, but a doctor may request an echocardiogram to ensure that your heart is functioning correctly and isn’t causing the cough.
Difficult cases may require additional testing:
- CT scan. A CT scan offers a more in-depth view of the airways and chest. It can be useful when determining the cause of a cough.
- Esophageal pH monitoring. If the CT scan doesn’t show the cause, your doctor may refer you to a gastrointestinal specialist or a pulmonary (lung) specialist. One of the tests these specialists may use is esophageal pH monitoring, which looks for evidence of GERD.
In cases where the previous treatments are either not possible or extremely unlikely to be successful, or the cough is expected to resolve without intervention, doctors may prescribe cough suppressants.
What’s the outcome if left untreated?
In most cases, a cough will disappear naturally within a week or two after it first develops. Coughing won’t typically cause any long-lasting damage or symptoms.
In some cases, a severe cough may cause temporary complications such as:
- fractured ribs
These are very rare, and they’ll normally cease when the cough disappears.
A cough that’s the symptom of a more serious condition is unlikely to go away on its own. If left untreated, the condition could worsen and cause other symptoms.
What preventive measures can be taken to avoid a cough?
While infrequent coughing is necessary to clear the airways, there are ways you can prevent other coughs.
Smoking is a common contributor to a chronic cough. It can be very difficult to cure a smoker’s cough.
There are a wide variety of methods available to help you stop smoking, from gadgets to advice groups and support networks. After you stop smoking, you’ll be much less likely to catch colds or experience a chronic cough.
An older study in 2004 found that people who ate diets high in fruit, fiber, and flavonoids were less likely to experience chronic respiratory symptoms such as a cough.
If you need help adjusting your diet, your doctor may be able to advise you or refer you to a dietitian.
If you can, you should avoid anyone with a contagious illness, such as bronchitis, to avoid coming into contact with germs.
Wash your hands frequently and don’t share utensils, towels, or pillows.
If you have existing medical conditions that increase your chances of developing a cough, such as GERD or asthma, consult your doctor about different management strategies. Once the condition is managed, you may find that your cough disappears, or becomes much less frequent.
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