Cough: Causes, Types & When to See a Doctor

What Is a Cough and Why Do We Cough?

Cough is a reflex action that protects your airways by forcefully expelling air to clear mucus, dust, irritants, and foreign particles from your lungs and throat. When something irritates the lining of your airways, nerve signals are sent to the brain's cough center, which triggers the muscles to contract and produce a cough.

Coughing is an essential protective mechanism that helps keep your respiratory system healthy. When you breathe in air, small particles, dust, bacteria, or viruses can enter your airways. The lining of your respiratory tract contains specialized cells that detect these irritants and initiate the cough reflex to expel them before they can cause harm. This same mechanism also helps clear excess mucus produced during infections or allergic reactions.

The cough reflex involves a complex coordination between your nervous system and multiple muscle groups. When the cough receptors in your throat, airways, or lungs are stimulated, they send signals through the vagus nerve to the cough center in your brainstem. This triggers a rapid sequence: you take a deep breath, your vocal cords close, your abdominal and chest muscles contract forcefully against the closed vocal cords, and then the vocal cords suddenly open, releasing air at speeds that can exceed 100 miles per hour. This powerful airflow helps dislodge and expel whatever is irritating your airways.

While coughing serves an important protective function, persistent or excessive coughing can be both distressing and debilitating. Understanding the different types of cough and their underlying causes is crucial for determining when self-care is appropriate and when medical attention is needed. The duration of a cough is one of the most important factors in identifying its cause: acute coughs lasting less than 3 weeks are usually caused by infections, while chronic coughs lasting more than 8 weeks often have different underlying causes that require investigation.

The role of mucus in coughing

Mucus plays a vital role in respiratory health, despite its unpleasant reputation. Your airways produce approximately 100 milliliters of mucus daily under normal conditions. This mucus forms a protective layer that traps particles, bacteria, and viruses before they can reach your lungs. Tiny hair-like structures called cilia constantly move the mucus upward toward your throat, where it is usually swallowed unconsciously.

When you have an infection or irritation, your airways produce more mucus and it often becomes thicker. This excess mucus accumulates faster than the cilia can clear it, triggering the cough reflex to help expel it. The color of your mucus can provide clues about what is happening in your airways: clear mucus is usually normal, white mucus often indicates congestion, yellow or green mucus may suggest infection (though this does not necessarily mean bacterial infection requiring antibiotics), and blood-tinged mucus always warrants medical attention.

What Are the Different Types of Cough?

Coughs are classified by duration (acute under 3 weeks, subacute 3-8 weeks, chronic over 8 weeks) and character (dry/non-productive vs wet/productive). A dry cough produces no mucus and feels irritating in the throat, while a productive cough brings up phlegm. Each type suggests different underlying causes.

Understanding the different types of cough helps identify potential causes and appropriate treatments. Healthcare providers typically classify coughs based on how long they have lasted and whether they produce mucus. This classification is not merely academic – it guides the diagnostic approach and treatment decisions. An acute cough that just started last week requires very different evaluation than a chronic cough that has persisted for months.

The character of your cough provides important diagnostic information. A dry, hacking cough that wakes you at night might suggest asthma or postnasal drip, while a wet, productive cough with green sputum could indicate bronchitis or pneumonia. Some conditions cause distinctive cough patterns: whooping cough produces characteristic "whooping" sounds between coughing fits, while croup in children causes a distinctive "barking" cough. Paying attention to these details can help you describe your symptoms accurately to healthcare providers.

Dry cough (non-productive cough)

A dry cough does not produce mucus or phlegm and often feels like a tickling or scratching sensation in the throat. This type of cough is particularly common at the beginning and end of viral respiratory infections, when inflammation irritates the airways without significant mucus production. Dry coughs can also be triggered by allergens, environmental irritants like smoke or pollution, certain medications (especially ACE inhibitors used for high blood pressure), and conditions like asthma or gastroesophageal reflux disease.

The persistent, irritating nature of dry coughs can be particularly troublesome because they do not provide the relief that comes from clearing mucus. Without mucus to expel, the coughing itself can further irritate the throat, creating a cycle of increasing discomfort. This is why treating the underlying cause and using soothing remedies like honey or warm fluids can be helpful for breaking this cycle. Dry coughs that persist for more than 3 weeks should be evaluated by a healthcare provider to identify the underlying cause.

Productive cough (wet cough)

A productive cough brings up mucus or phlegm from the lungs and airways. This type of cough serves an important function by helping clear excess secretions and preventing them from accumulating in your lungs where they could promote infection. Productive coughs are commonly associated with respiratory infections like bronchitis and pneumonia, chronic conditions like COPD and bronchiectasis, and situations where mucus production is increased such as during allergic responses.

While it may be tempting to suppress a productive cough, doing so can actually be counterproductive because the mucus needs to be cleared from your airways. Instead of cough suppressants, treatment focuses on thinning the mucus (by staying well hydrated) and treating the underlying condition. The appearance of the mucus can provide valuable information: clear or white mucus is typical of viral infections and allergies, while yellow or green mucus indicates the presence of immune cells fighting infection. Rust-colored or blood-tinged mucus requires prompt medical evaluation.

What Causes a Cough?

The most common cause of acute cough is viral respiratory infection (common cold, flu, COVID-19). Chronic cough lasting over 8 weeks is usually caused by postnasal drip syndrome, asthma (including cough-variant asthma), or gastroesophageal reflux disease (GERD). Less common causes include COPD, lung infections, ACE inhibitor medications, and rarely, lung cancer.

Understanding the cause of your cough is essential for effective treatment. Acute coughs that develop suddenly and last less than 3 weeks are almost always caused by viral upper respiratory infections – what we commonly call colds or flu. These infections trigger inflammation in the airways, increase mucus production, and make the cough receptors more sensitive. While frustrating, these coughs serve the important purpose of clearing infected secretions from your respiratory tract.

Chronic coughs that persist for more than 8 weeks have a different set of underlying causes. Research has shown that three conditions account for most cases of chronic cough in non-smokers with normal chest X-rays: postnasal drip syndrome (mucus dripping from the nose down the back of the throat), asthma (including a variant that presents primarily with cough rather than wheezing), and gastroesophageal reflux disease (acid from the stomach reaching the throat or airways). Identifying which of these conditions is responsible often requires systematic investigation and sometimes trial treatments.

Viral infections

Viral respiratory infections are by far the most common cause of cough, responsible for most acute coughs worldwide. The common cold, caused by over 200 different viruses (most commonly rhinoviruses), typically produces symptoms including cough, runny nose, sore throat, and mild fatigue. While most cold symptoms improve within 4-5 days, the cough often persists longer because the airways remain sensitized and irritated even after the infection clears. This post-viral cough can last up to 4 weeks and is generally not a cause for concern unless it worsens or new symptoms develop.

Influenza (flu) causes more severe symptoms than the common cold, including high fever (often 39-40°C/102-104°F), severe body aches, headache, and fatigue that can last for weeks. The cough associated with influenza tends to be more severe and persistent than that of a cold. COVID-19 can also cause significant cough, often described as dry and persistent, sometimes lasting for weeks to months after the initial infection (sometimes called "long COVID"). Vaccination against both influenza and COVID-19 can reduce the severity of illness and associated cough.

Bronchitis and lower respiratory infections

Acute bronchitis is inflammation of the bronchial tubes, the airways that carry air to and from your lungs. It often develops as a complication of a cold when the infection spreads to the lower airways. Symptoms include cough that may be dry initially but often becomes productive, chest discomfort especially when coughing, fatigue, and sometimes low-grade fever. Acute bronchitis is usually caused by viruses and resolves within 2-3 weeks without antibiotics, although the cough may linger for up to 4 weeks.

Pneumonia is a more serious lung infection that causes inflammation of the air sacs in the lungs. Unlike bronchitis, pneumonia often causes high fever, shortness of breath, chest pain that worsens with breathing, and productive cough with colored sputum. Bacterial pneumonia requires antibiotic treatment, while viral pneumonia is treated supportively. Anyone with symptoms suggesting pneumonia – especially high fever, significant shortness of breath, or chest pain – should seek medical attention promptly.

Asthma and allergies

Asthma is a chronic inflammatory condition of the airways that affects approximately 300 million people worldwide. While wheezing and shortness of breath are classic symptoms, cough can be the predominant or even sole symptom in some patients – a condition known as cough-variant asthma. Asthma-related cough typically worsens at night or early morning, after exercise, when exposed to cold air, or when encountering triggers like allergens (pollen, dust mites, pet dander), irritants (smoke, strong odors), or respiratory infections.

Allergic rhinitis (hay fever) can cause cough through a mechanism called postnasal drip. When the nasal passages become inflamed by allergens, they produce excess mucus that drips down the back of the throat, triggering the cough reflex. This type of cough may be accompanied by other allergy symptoms like sneezing, itchy eyes, and nasal congestion. It often follows a seasonal pattern corresponding to pollen seasons, though year-round allergens like dust mites can cause persistent symptoms.

Gastroesophageal reflux disease (GERD)

Gastroesophageal reflux disease occurs when stomach acid regularly flows back into the esophagus. While heartburn is the most recognized symptom, many people with GERD-related cough experience no heartburn at all – this is called "silent reflux" or laryngopharyngeal reflux. The acid can irritate the throat and airways, triggering cough, hoarseness, throat clearing, and a sensation of something stuck in the throat. GERD-related cough often worsens after meals, when lying down, or after consuming trigger foods and beverages like coffee, chocolate, spicy foods, and alcohol.

The mechanism by which GERD causes cough is twofold: direct irritation when acid reaches the throat or airways, and a reflex mechanism where acid in the lower esophagus triggers coughing through nerve pathways. Treatment typically involves dietary modifications, avoiding eating close to bedtime, elevating the head of the bed, and medications that reduce stomach acid production. Improvement in cough may take several weeks to months of consistent treatment.

COPD and chronic bronchitis

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease that makes breathing difficult. It is almost always caused by long-term exposure to lung irritants, with cigarette smoking being the primary cause. COPD includes chronic bronchitis (long-term inflammation of the bronchial tubes with persistent cough and mucus production) and emphysema (damage to the air sacs). The characteristic symptom is a chronic productive cough, often called "smoker's cough," along with shortness of breath and reduced exercise tolerance.

COPD typically develops gradually over many years and is rare in people under 40 who have never smoked. Symptoms may be mild initially and easily attributed to aging or being out of shape, but they progressively worsen over time. While COPD cannot be cured, treatments can relieve symptoms, slow progression, and improve quality of life. The single most important intervention is quitting smoking – it is never too late to benefit from stopping.

Medications that cause cough

Certain medications can cause persistent dry cough as a side effect. The most notable are ACE inhibitors, a class of drugs commonly prescribed for high blood pressure and heart failure (examples include lisinopril, enalapril, and ramipril). ACE inhibitor cough occurs in approximately 10-15% of patients and can develop at any time during treatment – sometimes starting months or even years after beginning the medication. The cough is typically dry, tickling, and persistent, often worse at night.

If you develop a persistent cough while taking an ACE inhibitor, speak with your healthcare provider. The cough usually resolves within 1-4 weeks of stopping the medication, and alternative blood pressure medications (such as ARBs) are available that rarely cause cough. Do not stop blood pressure medications without consulting your doctor, as this can be dangerous.

What Can I Do at Home to Relieve Cough?

For most coughs, home remedies are effective: stay well hydrated with warm fluids, use honey (1-2 teaspoons for adults and children over 1 year), elevate your head when sleeping, avoid irritants like smoke, and use a humidifier if indoor air is dry. These measures are often as effective as over-the-counter cough medications.

The good news is that most coughs can be effectively managed at home with simple measures. Staying well hydrated is one of the most important things you can do – fluids help thin mucus, making it easier to cough up, and keep your throat moist. Warm fluids like tea, broth, and warm water with lemon can be particularly soothing. There is no need for special "medicinal" teas; any warm, comforting fluid will help.

Rest is important because your body needs energy to fight infection. When you are sick with a respiratory infection, staying home not only helps you recover faster but also prevents spreading illness to others. Most viral respiratory infections are contagious for the first few days of symptoms. Getting adequate sleep also supports your immune system function.

Honey: nature's cough medicine

Honey has been used as a cough remedy for thousands of years, and modern research supports its effectiveness. Multiple clinical trials have shown that honey is as effective as, or more effective than, common over-the-counter cough medications for reducing cough frequency and severity. The World Health Organization (WHO) recommends honey as a safe, low-cost treatment for cough in adults and children over 12 months of age.

The recommended dose is 1-2 teaspoons of honey taken directly or mixed with warm water or tea. Honey can be taken before bedtime to help with nighttime coughing. The mechanism is not fully understood but likely involves honey's soothing effect on the throat, its antimicrobial properties, and its ability to stimulate saliva production. Any type of honey appears to be effective, though some studies suggest darker honeys may have greater antioxidant properties.

Other effective home remedies

Elevating your head when sleeping can significantly reduce nighttime coughing, especially if you have postnasal drip or acid reflux. You can use extra pillows, or for better back support, place blocks or books under the legs at the head of your bed to raise it 6-8 inches. This helps prevent mucus from pooling in the back of your throat and reduces acid reflux during sleep.

Keeping indoor air moist with a humidifier can help if you live in a dry climate or during winter when heating dries indoor air. Dry air can irritate the airways and worsen cough. However, be sure to clean your humidifier regularly to prevent mold and bacteria growth. Alternatively, taking a warm shower and breathing the steam can provide temporary relief.

Avoiding respiratory irritants is crucial. If you smoke, this is an excellent reason to quit – smoking irritates the airways and prolongs cough from any cause. Stay away from secondhand smoke as well. Other irritants to avoid include strong perfumes, cleaning chemicals, dust, and air pollution when possible.

Over-the-counter medications

The scientific evidence for over-the-counter cough medications is surprisingly limited. Most studies show these medications provide modest benefit at best. That said, some people find them helpful, and they can be tried for short-term symptom relief. Understanding the different types can help you choose appropriately:

• Cough suppressants (antitussives): Medications like dextromethorphan or noscapine work by suppressing the cough reflex. They may be appropriate for dry, non-productive cough that disrupts sleep. However, suppressing a productive cough that is clearing mucus from your lungs is generally not advisable.
• Expectorants: Medications like guaifenesin are intended to thin mucus and make it easier to cough up. Evidence for their effectiveness is limited, and staying well hydrated may be equally effective.
• Decongestants: Pseudoephedrine or phenylephrine can help if your cough is caused by postnasal drip from nasal congestion. They should be used with caution in people with high blood pressure or heart conditions.
• Antihistamines: First-generation antihistamines like diphenhydramine may help cough caused by allergies or postnasal drip, partly through their drying effect on secretions. They can cause drowsiness.

When using over-the-counter medications, follow package directions carefully and do not exceed recommended doses. Be aware that many combination products contain multiple active ingredients – check labels to avoid accidentally doubling up on ingredients if taking multiple products.

When Should You See a Doctor for a Cough?

See a doctor if your cough lasts more than 4 weeks, you cough up blood, you have difficulty breathing or chest pain when breathing, you have a fever lasting more than 4 days, or you experience unexplained weight loss. Seek emergency care immediately for severe difficulty breathing, high fever with confusion, or coughing up large amounts of blood.

While most coughs are harmless and resolve on their own, certain signs and symptoms warrant medical evaluation. The duration of cough is an important factor – a cough that persists beyond 4 weeks should be evaluated even if it seems to be slowly improving. Chronic cough can significantly impact quality of life and often has a treatable underlying cause.

The character of your cough and accompanying symptoms help determine the urgency of evaluation. A cough with mild cold symptoms that is gradually improving can usually be safely monitored at home. However, a cough that is getting worse rather than better, or one accompanied by concerning symptoms like blood, fever, chest pain, or weight loss, should prompt earlier evaluation.

Symptoms that require prompt medical attention

Contact your healthcare provider soon if you experience any of the following:

• Cough lasting more than 4 weeks that is not improving
• Coughing up blood (hemoptysis) – even small amounts warrant evaluation
• Fever over 38°C (100.4°F) lasting more than 4 days
• Worsening shortness of breath or difficulty breathing with exertion
• Chest pain that worsens when you breathe deeply or cough
• Unintentional weight loss
• Night sweats
• Whooping cough exposure – especially important if you are pregnant or have close contact with infants

How Is the Cause of Cough Diagnosed?

Diagnosis starts with medical history and physical examination. For persistent cough, tests may include chest X-ray to check for pneumonia or other lung conditions, spirometry to test lung function, and sometimes blood tests. Additional tests like CT scan, bronchoscopy, or pH monitoring may be needed for chronic cough that does not respond to initial treatment.

Diagnosing the cause of cough involves systematic evaluation starting with a thorough medical history. Your doctor will ask about the duration and character of your cough, whether it produces mucus and what the mucus looks like, when the cough is worst, what makes it better or worse, associated symptoms, your smoking history, medications you take, and your work and home environment. This information alone often suggests the likely cause.

Physical examination includes listening to your lungs with a stethoscope (auscultation), examining your nose and throat, checking your lymph nodes, and observing your breathing pattern. Abnormal breath sounds like wheezing, crackles, or decreased breath sounds in certain areas can point toward specific diagnoses.

Common diagnostic tests

For acute cough in otherwise healthy adults, testing is often unnecessary as the cause is usually viral infection that will resolve on its own. However, for persistent or concerning cough, various tests may be helpful:

• Chest X-ray: Often the first test for persistent cough, it can reveal pneumonia, lung tumors, heart enlargement, or other lung abnormalities. A normal chest X-ray is reassuring and helps direct further evaluation.
• Spirometry: A lung function test that measures how much air you can exhale and how quickly. It is essential for diagnosing asthma and COPD. You may be asked to repeat the test after using a bronchodilator inhaler to see if your lung function improves.
• Blood tests: May include complete blood count to check for infection or inflammation, and sometimes specific tests like allergy testing (IgE levels) or tests for specific infections.
• Sputum culture: If you are coughing up sputum, it may be sent to the laboratory to identify bacteria or other organisms causing infection.

Additional tests for chronic cough

When chronic cough does not respond to initial treatment or the cause remains unclear, additional testing may include:

• CT scan of the chest: Provides more detailed images than X-ray and can detect smaller abnormalities, bronchiectasis, or interstitial lung disease.
• Bronchoscopy: A flexible scope passed through your nose or mouth into your airways allows direct visualization and can take samples if needed.
• Esophageal pH monitoring: A test where a thin tube measures acid levels in your esophagus over 24 hours to diagnose GERD-related cough.
• Methacholine challenge test: A specialized test for asthma where you inhale a substance that causes airway narrowing in people with asthma.

How Is Cough Treated?

Treatment depends on the underlying cause. Acute viral cough is treated with supportive care (rest, fluids, honey). Specific treatments target underlying conditions: inhalers for asthma, acid-reducing medications for GERD, antihistamines and nasal steroids for postnasal drip. Antibiotics are only helpful for bacterial infections, not viral coughs. Chronic unexplained cough may respond to specialized medications or speech therapy techniques.

Effective cough treatment requires identifying and addressing the underlying cause rather than simply suppressing the cough. For most acute coughs caused by viral infections, treatment focuses on symptom relief and supporting your body's natural healing process. This includes rest, adequate hydration, honey for cough relief, and over-the-counter medications as needed for comfort.

For chronic cough, treatment is directed at the specific underlying condition. This often involves a systematic approach, starting with treatment for the most likely cause and moving to alternative diagnoses if the first treatment is unsuccessful. Sometimes multiple conditions contribute to chronic cough and all need to be addressed.

Treatment by underlying cause

Postnasal drip syndrome: First-line treatment typically includes a first-generation antihistamine (like chlorpheniramine or diphenhydramine) combined with a decongestant. Nasal corticosteroid sprays (like fluticasone or budesonide) are effective for allergic causes. Nasal saline irrigation can also help. Improvement may take 2-4 weeks of consistent treatment.

Asthma and cough-variant asthma: Treatment involves inhaled corticosteroids as maintenance therapy and bronchodilators (like albuterol/salbutamol) for symptom relief. For cough-variant asthma, the response to treatment may take 6-8 weeks. Your doctor may adjust medications based on response and may add other controller medications if needed.

Gastroesophageal reflux disease: Treatment includes lifestyle modifications (avoiding trigger foods, not eating close to bedtime, elevating the head of the bed) and acid-reducing medications. Proton pump inhibitors (like omeprazole or pantoprazole) are typically more effective than H2 blockers for GERD-related cough. Improvement may take 2-3 months of consistent treatment.

ACE inhibitor cough: If an ACE inhibitor is causing your cough, your doctor can switch you to an alternative medication (usually an ARB like losartan or valsartan). The cough typically resolves within 1-4 weeks of stopping the ACE inhibitor.

Infections: Viral infections do not require antibiotics and are treated supportively. Bacterial infections like bacterial pneumonia require antibiotics specific to the causative organism. Tuberculosis requires specialized long-term antibiotic treatment. Whooping cough (pertussis) is treated with antibiotics primarily to reduce transmission to others, as antibiotics have limited effect on symptom duration once the cough is established.

When cough remains unexplained

In some cases, chronic cough persists despite thorough evaluation and treatment of identified causes. This condition, sometimes called unexplained chronic cough or refractory chronic cough, may respond to specialized treatments including low-dose morphine or gabapentin (which act on the cough reflex), or speech therapy techniques that teach methods to suppress the urge to cough. These treatments should be supervised by specialists experienced in managing chronic cough.