Cough: Causes, Types & When to See a Doctor

What Is a Cough and Why Does It Happen?

A cough is a protective reflex that helps clear the airways of mucus, irritants, and foreign particles. It occurs when sensory nerves in the respiratory tract are stimulated, triggering a forceful expulsion of air from the lungs. While coughing is usually beneficial, persistent or severe coughing can indicate underlying disease and may require medical evaluation.

Coughing is one of the most fundamental protective mechanisms of the human body. When you cough, your body is actively working to keep your airways clear and prevent harmful substances from entering your lungs. The cough reflex involves a complex coordination between your nervous system, respiratory muscles, and airways that has evolved over millions of years to protect you from respiratory threats.

The cough reflex begins when specialized nerve receptors in your throat, trachea, and bronchi detect potential threats. These receptors are exquisitely sensitive to various stimuli including mechanical irritation, chemical irritants, temperature changes, and inflammatory mediators. When stimulated, these nerves send signals to the cough center in your brainstem, which then coordinates the three phases of a cough: the inspiratory phase (deep breath in), the compressive phase (closure of the glottis with contraction of expiratory muscles), and the expulsive phase (sudden opening of the glottis with forceful air expulsion).

The force generated during a cough is remarkable. Air can be expelled from the lungs at speeds up to 500 miles per hour (800 km/h), creating enough force to clear mucus, debris, and pathogens from the airways. This powerful mechanism is essential for maintaining respiratory health, but when it becomes excessive or chronic, it can significantly impact quality of life and may signal the presence of disease.

The difference between productive and non-productive cough

Healthcare providers classify coughs into two main categories based on whether they produce mucus. A productive cough (also called a wet cough) brings up phlegm or mucus from the lower respiratory tract. This type of cough serves an important function by helping to clear secretions from the airways and is common in conditions like bronchitis, pneumonia, and chronic obstructive pulmonary disease (COPD).

A non-productive cough (also called a dry cough) does not produce mucus and often feels like a tickle or irritation in the throat. Dry coughs are commonly caused by viral upper respiratory infections, allergies, asthma, gastroesophageal reflux, and certain medications, particularly ACE inhibitors used for high blood pressure. The treatment approach often differs between these two types of cough, which is why accurately describing your cough to a healthcare provider is important.

Acute versus chronic cough

Coughs are also classified by their duration. An acute cough lasts less than 3 weeks and is most commonly caused by upper respiratory tract infections such as the common cold, flu, or COVID-19. A subacute cough persists for 3 to 8 weeks and often represents a post-infectious cough that occurs after a respiratory infection has resolved. A chronic cough lasts longer than 8 weeks and almost always requires medical investigation to identify and treat the underlying cause.

What Causes Cough?

The most common causes of acute cough are viral respiratory infections, while chronic cough is most often caused by postnasal drip (upper airway cough syndrome), asthma, and gastroesophageal reflux disease (GERD). Other important causes include medications (particularly ACE inhibitors), smoking, environmental irritants, and less commonly, serious conditions like lung cancer or tuberculosis.

Understanding the cause of your cough is essential for effective treatment. The causes of cough vary significantly depending on whether the cough is acute or chronic, and identifying the underlying cause is the key to successful management. Research has shown that in the vast majority of cases, chronic cough can be attributed to one or more of just a few conditions, and that treating these underlying causes leads to resolution of the cough in most patients.

The respiratory tract is exposed to the external environment with every breath, making it vulnerable to a wide range of irritants and pathogens. From the nose down to the smallest airways in the lungs, various conditions can trigger the cough reflex. Some causes are immediately obvious, such as choking on food or water, while others may be more subtle and require careful medical evaluation to identify.

Acute cough causes

Viral upper respiratory tract infections are by far the most common cause of acute cough, responsible for approximately 90% of cases. The common cold, influenza, COVID-19, and other respiratory viruses trigger inflammation in the airways that stimulates cough receptors. These infections typically cause cough that lasts 1-3 weeks, though in some cases a post-infectious cough may persist for several weeks after other symptoms have resolved.

Other causes of acute cough include acute bronchitis (often viral in origin), bacterial pneumonia, exacerbations of chronic conditions like asthma or COPD, exposure to environmental irritants, and aspiration of food or liquid. Acute cough can also be the presenting symptom of more serious conditions like pulmonary embolism or heart failure, which is why new-onset cough accompanied by other concerning symptoms should prompt medical evaluation.

Chronic cough causes

The "big three" causes of chronic cough in non-smokers with normal chest X-rays account for up to 90% of cases:

• Upper airway cough syndrome (postnasal drip): Mucus from the nose and sinuses drips down the back of the throat, triggering the cough reflex. This is associated with allergic rhinitis, chronic sinusitis, and non-allergic rhinitis.
• Asthma: Cough may be the only symptom of asthma, a condition known as cough-variant asthma. This is characterized by chronic cough that worsens at night or with exercise and responds to asthma medications.
• Gastroesophageal reflux disease (GERD): Stomach acid refluxing into the esophagus and sometimes the throat can trigger cough, even without typical heartburn symptoms. This mechanism, sometimes called "silent reflux," is increasingly recognized as a major cause of chronic cough.

Other important causes of chronic cough include medications (especially ACE inhibitors, which cause cough in 5-20% of users), chronic bronchitis from smoking, eosinophilic bronchitis, and less commonly, serious conditions such as lung cancer, tuberculosis, interstitial lung disease, and bronchiectasis.

What Are the Symptoms Associated with Cough?

Cough symptoms vary depending on the underlying cause. Common associated symptoms include nasal congestion and postnasal drip, wheezing and shortness of breath, heartburn and acid taste, fever and body aches, and mucus production. The characteristics of the cough itself—whether dry or productive, timing, and triggers—provide important diagnostic clues.

While cough itself is a symptom rather than a disease, the characteristics of your cough and the symptoms that accompany it can provide valuable information about its cause. Healthcare providers pay close attention to the nature of your cough, when it occurs, what makes it better or worse, and what other symptoms you experience. This information guides the diagnostic process and helps determine the most appropriate treatment.

The timing of your cough often provides diagnostic clues. A cough that is worse at night may suggest asthma, postnasal drip, or GERD. A cough that occurs primarily in the morning may indicate chronic bronchitis or bronchiectasis, as secretions that accumulated overnight are cleared upon waking. A cough triggered by talking, laughing, or cold air may suggest airway hyperreactivity, while a cough that follows meals may point to reflux or aspiration.

Characteristics of different types of cough

A barking cough that sounds like a seal often indicates croup in children, caused by viral infection of the larynx and trachea. A whooping cough characterized by spasms of coughing followed by a high-pitched "whoop" is classic for pertussis (whooping cough), though adults may not always develop the characteristic whoop. A honking or brassy cough that disappears during sleep may suggest habit cough or psychogenic cough.

The color of mucus produced during coughing is often misinterpreted. While green or yellow mucus is commonly believed to indicate bacterial infection, the color actually reflects the presence of white blood cells and their enzymes rather than bacteria. Viral infections can produce colored mucus, and clear mucus does not exclude bacterial infection. However, blood-tinged mucus or frank blood in sputum (hemoptysis) always warrants medical evaluation.

Warning symptoms that require medical attention

Certain symptoms accompanying cough should prompt urgent or emergent medical evaluation:

• Hemoptysis (coughing up blood): May indicate lung cancer, tuberculosis, bronchiectasis, or pulmonary embolism
• Severe shortness of breath: May suggest pneumonia, asthma exacerbation, heart failure, or pulmonary embolism
• Chest pain with coughing: May indicate pneumonia, pulmonary embolism, or pleurisy
• Unexplained weight loss: Red flag for malignancy or tuberculosis
• High fever (above 39°C/102°F): Suggests significant infection requiring evaluation
• Night sweats: May indicate tuberculosis or lymphoma

When Should You See a Doctor for a Cough?

See a doctor if your cough lasts more than 3 weeks, you cough up blood, you have difficulty breathing or chest pain, you have unexplained weight loss, or you have a high fever. Seek emergency care for severe breathing difficulties, choking, or if you cannot speak due to coughing. Most acute coughs from colds do not require medical attention and resolve on their own.

Knowing when to seek medical care for a cough can be challenging. The vast majority of coughs, particularly those associated with common colds and minor respiratory infections, will resolve on their own without medical treatment. However, certain features of a cough indicate the need for professional evaluation, and recognizing these warning signs is important for receiving timely and appropriate care.

The duration of your cough is one of the most important factors in determining whether you need medical evaluation. Most acute coughs from viral infections resolve within 1-3 weeks. If your cough persists beyond 3 weeks, you should consult a healthcare provider. A cough lasting more than 8 weeks is considered chronic and almost always warrants thorough investigation to identify the underlying cause.

Schedule a non-urgent medical appointment if your cough has lasted more than 3 weeks, if you have recurrent episodes of cough, if over-the-counter treatments are not providing relief, if you are a smoker with a new or changing cough, if you take blood pressure medications (particularly ACE inhibitors), or if your cough is significantly affecting your quality of life, sleep, or ability to work.

How Is the Cause of Cough Diagnosed?

Diagnosing the cause of cough involves a detailed medical history, physical examination, and targeted testing based on suspected causes. Common tests include chest X-ray, spirometry (lung function testing), and sometimes CT scan, bronchoscopy, or esophageal pH monitoring. In many cases, a trial of treatment for the most likely cause is used as both a diagnostic and therapeutic approach.

The evaluation of chronic cough follows an evidence-based, systematic approach that has been validated in numerous studies. This approach recognizes that despite the many possible causes of chronic cough, a small number of conditions account for the vast majority of cases. By evaluating and treating these common causes in an orderly fashion, most patients with chronic cough can be successfully diagnosed and treated.

The medical history is the cornerstone of cough evaluation. Your doctor will ask detailed questions about the characteristics of your cough, when it started, what makes it better or worse, associated symptoms, your smoking history, medications you take, your occupation and environmental exposures, and your past medical history. This information often points strongly toward the likely cause and guides further testing.

Physical examination findings

The physical examination focuses on the upper and lower respiratory tract but also includes examination of other systems that may contribute to cough. Your doctor will examine your nasal passages for signs of rhinitis or sinusitis, your throat for postnasal drip or signs of reflux, and your lungs for wheezing, crackles, or other abnormal breath sounds. Examination of your heart may reveal signs of heart failure, which can cause cough through fluid accumulation in the lungs.

Diagnostic tests

Testing is guided by the clinical history and examination findings. Common tests in the evaluation of chronic cough include:

• Chest X-ray: Usually the first imaging test, used to rule out pneumonia, lung masses, and other visible abnormalities
• Spirometry: Measures lung function and can identify asthma and COPD. Bronchodilator challenge testing can unmask hidden asthma
• Methacholine challenge test: Highly sensitive for diagnosing asthma when spirometry is normal
• CT scan of the chest: Provides detailed imaging when chest X-ray is inconclusive or when more serious conditions are suspected
• CT scan of the sinuses: May be performed when chronic sinusitis is suspected
• Esophageal pH monitoring: Measures acid reflux over 24 hours to diagnose GERD-related cough
• Bronchoscopy: Direct visualization of the airways, used when other tests are inconclusive or when airway abnormalities are suspected

How Is Cough Treated?

Treatment depends on the underlying cause. For acute cough from viral infections, supportive care with fluids, rest, and honey (for children over 1 year and adults) is often sufficient. For chronic cough, treatment targets the underlying cause: antihistamines and nasal steroids for postnasal drip, inhaled corticosteroids for asthma, proton pump inhibitors for GERD, or stopping ACE inhibitors if medication-induced.

The fundamental principle of cough treatment is to address the underlying cause rather than simply suppressing the cough reflex. While cough suppressants may provide temporary relief of symptoms, they do not treat the root cause and may mask important warning signs. For this reason, the identification and treatment of the underlying condition is paramount, particularly for chronic cough.

For acute cough due to respiratory infections, the mainstay of treatment is supportive care. This includes adequate hydration, rest, and symptomatic relief measures. Most acute coughs resolve within 1-3 weeks regardless of treatment, and antibiotics are not effective for viral infections, which cause the vast majority of acute coughs. The judicious use of cough suppressants may be appropriate for sleep-disrupting dry coughs, but should not be used for productive coughs where clearing mucus is beneficial.

Home remedies and self-care

Several evidence-based home remedies can help relieve cough symptoms:

• Honey: Multiple studies have shown that honey is as effective as some over-the-counter cough suppressants, particularly for nighttime cough in children. Take 1-2 teaspoons directly or mixed in warm water or tea. Do not give honey to children under 1 year due to botulism risk.
• Fluids: Staying well-hydrated helps thin mucus and keeps airways moist. Warm liquids like tea, broth, and warm water with lemon may be particularly soothing.
• Humidified air: Using a cool-mist humidifier adds moisture to the air and can soothe irritated airways. Clean the humidifier regularly to prevent mold growth.
• Elevation: Sleeping with your head elevated can reduce postnasal drip and GERD-related cough at night.
• Avoiding irritants: Stay away from smoke, strong perfumes, and other airborne irritants that can worsen cough.

Medical treatment by cause

For postnasal drip/upper airway cough syndrome: First-generation antihistamines (like chlorpheniramine or diphenhydramine), decongestants, and intranasal corticosteroid sprays form the mainstay of treatment. Newer, non-sedating antihistamines are less effective for this condition. If allergies are the underlying cause, allergen avoidance and possibly immunotherapy may be recommended.

For asthma and cough-variant asthma: Inhaled corticosteroids are the cornerstone of treatment, often combined with short-acting or long-acting bronchodilators. Leukotriene modifiers may be added for additional control. Treatment typically requires 6-8 weeks before cough fully resolves.

For GERD-related cough: Proton pump inhibitors (PPIs) like omeprazole or esomeprazole are first-line treatment, often requiring higher doses and longer duration than for typical heartburn. Lifestyle modifications including weight loss, avoiding late meals, and elevating the head of the bed complement medical therapy. Treatment may need to continue for 2-3 months before cough improves.

For medication-induced cough: If ACE inhibitors are the culprit, switching to an angiotensin receptor blocker (ARB) typically resolves the cough within 1-4 weeks, though it may take up to 3 months in some cases.

What About Cough in Children?

Cough in children is usually caused by viral respiratory infections and typically resolves within 1-3 weeks. Honey (for children over 1 year) is an effective and safe remedy. Over-the-counter cough medicines are not recommended for children under 6 years due to lack of proven benefit and potential for harm. See a doctor if your child has breathing difficulty, high fever, or cough lasting more than 2 weeks.

Children experience an average of 6-10 respiratory infections per year, many of which cause cough. While this frequency may seem alarming to parents, it is normal and helps develop the child's immune system. Most coughs in children are caused by viruses and do not require antibiotics or prescription medications.

The approach to treating cough in children differs from adults for several important reasons. First, over-the-counter cough and cold medicines have not been proven effective in children and may cause serious side effects, including sedation, paradoxical excitation, and in rare cases, death. The FDA advises against using these products in children under 2 years, and many experts recommend avoiding them in children under 6 years.

Honey has emerged as the preferred treatment for acute cough in children over 1 year old. Multiple randomized controlled trials have demonstrated that honey reduces cough frequency and severity and improves sleep for both the child and parents. A typical dose is ½ to 1 teaspoon for children aged 1-5 years and 1-2 teaspoons for older children, given directly or mixed in warm water. Honey should never be given to children under 1 year due to the risk of infant botulism.

How Can You Prevent Cough?

Preventing cough primarily involves avoiding respiratory infections through hand hygiene, avoiding close contact with sick individuals, and staying up-to-date on vaccinations (flu, COVID-19, pertussis). For chronic cough prevention, addressing underlying conditions, quitting smoking, avoiding known triggers, and maintaining good indoor air quality are key strategies.

Prevention of cough focuses on two main strategies: preventing the respiratory infections that cause most acute coughs, and controlling the chronic conditions that lead to persistent cough. While not all coughs can be prevented, many can be avoided or minimized through appropriate preventive measures.

Respiratory infections spread primarily through respiratory droplets and contact with contaminated surfaces. Regular hand washing with soap and water for at least 20 seconds, or using alcohol-based hand sanitizer when soap is not available, is one of the most effective ways to prevent respiratory infections. Avoiding touching your face, particularly your eyes, nose, and mouth, reduces the chance of introducing viruses from contaminated hands.

Vaccination

Vaccines are powerful tools for preventing respiratory infections that cause cough:

• Influenza vaccine: Annual flu vaccination is recommended for everyone over 6 months of age and can prevent flu-related cough and complications
• COVID-19 vaccine: Staying up-to-date with recommended COVID-19 vaccines helps prevent severe disease and persistent post-COVID cough
• Pertussis (whooping cough) vaccine: Included in childhood vaccination series (DTaP) and recommended as a booster (Tdap) for adolescents, adults, and pregnant women
• Pneumococcal vaccine: Recommended for children, adults over 65, and those with certain medical conditions to prevent pneumococcal pneumonia

Lifestyle measures

Quit smoking: Smoking is the leading preventable cause of chronic cough. Quitting smoking not only prevents smoker's cough but also reduces the risk of lung cancer, COPD, and heart disease. The cough may temporarily worsen after quitting as the airways heal, but this is a positive sign.

Manage underlying conditions: For those with asthma, allergies, or GERD, consistent management of these conditions prevents cough flares. Taking medications as prescribed, even when feeling well, is essential for prevention.

Improve indoor air quality: Using air purifiers, maintaining proper humidity levels (30-50%), avoiding indoor pollutants, and ensuring good ventilation can reduce respiratory irritants that trigger cough.

What Are the Complications of Chronic Cough?

Chronic cough can lead to physical complications including urinary incontinence, rib fractures, syncope (fainting), and sleep disturbances. The psychological impact includes embarrassment, social isolation, anxiety, and depression. Quality of life is significantly affected, with impacts on work productivity and personal relationships. These complications underscore the importance of proper diagnosis and treatment.

While coughing is generally a beneficial reflex, chronic cough can have significant negative effects on health and quality of life. The physical force of repeated coughing can stress various body systems, and the constant symptom burden takes a psychological toll. Understanding these potential complications emphasizes why chronic cough should not be dismissed as merely bothersome but should be thoroughly evaluated and treated.

Physical complications of chronic cough include stress urinary incontinence (particularly in women), which occurs in up to 55% of women with chronic cough. The forceful abdominal contractions during coughing overcome the urethral sphincter, leading to urine leakage. Rib fractures can occur from severe, repeated coughing, particularly in those with osteoporosis. Cough syncope (fainting) results from the increased intrathoracic pressure during prolonged coughing episodes, which temporarily reduces blood flow to the brain.

The impact on sleep quality is substantial. Nighttime cough disrupts sleep for both the patient and bed partners, leading to daytime fatigue, impaired concentration, and reduced quality of life. Studies have shown that patients with chronic cough have worse quality of life scores than many patients with other chronic conditions.