🩺 Cough

## Overview Cough is one of the most common symptoms prompting medical consultation worldwide. Defined as a sudden, forceful expulsion of air from the lungs, cough serves as a critical protective reflex that clears the airways of mucus, irritants, and foreign particles. The cough reflex arc involves sensory receptors in the pharynx, larynx, trachea, and bronchi; vagal afferent nerves; a brainstem cough center; and efferent motor pathways to the diaphragm, intercostal muscles, and abdominal muscles [1]. Clinically, cough is classified by duration: **acute** (fewer than 3 weeks), **subacute** (3–8 weeks), and **chronic** (more than 8 weeks) [1]. Acute cough is overwhelmingly caused by viral upper respiratory tract infections (URTIs), while chronic cough affects an estimated 5–10 % of the adult population globally and is associated with significant impairment of quality of life, including sleep disruption, urinary incontinence, musculoskeletal pain, and social embarrassment [2]. Cough accounts for roughly 30 million office visits per year in the United States alone, and over-the-counter (OTC) cough and cold preparations represent a multibillion-dollar market. Because cough can signal conditions ranging from the benign common cold to life-threatening malignancies, understanding when self-care is appropriate and when escalation is required is essential. --- ## Common Causes The following causes are ranked approximately by frequency in the general adult population. The underlying mechanism is noted for each. ### Acute Cough (< 3 weeks) 1. **Viral upper respiratory tract infection (common cold, influenza, COVID-19)** — Viral invasion of respiratory epithelium triggers inflammation, increased mucus production, and stimulation of cough receptors. This is by far the most frequent cause of acute cough and is usually self-limiting within 7–14 days. 2. **Acute bronchitis** — Often post-viral, inflammation of the bronchial mucosa leads to mucosal edema and mucus hypersecretion. Cough may persist for 2–3 weeks after other symptoms resolve. 3. **Acute sinusitis** — Infected sinus contents drain posteriorly (post-nasal drip), stimulating pharyngeal and laryngeal cough receptors. 4. **Allergic rhinitis / environmental irritant exposure** — Allergens or inhaled irritants (smoke, dust, fumes) activate mast cells and sensory nerve endings in the airways. 5. **Pneumonia** — Bacterial, viral, or atypical pathogens cause alveolar and bronchial inflammation with exudate accumulation. Cough is typically productive, often with fever and dyspnea. 6. **Acute exacerbation of asthma or COPD** — Trigger-induced bronchospasm, mucosal edema, and mucus plugging narrow the airways and stimulate cough. ### Chronic Cough (> 8 weeks) The classic diagnostic triad accounts for approximately 90 % of chronic cough cases in non-smokers with a normal chest radiograph who are not taking ACE inhibitors [4]: 1. **Upper airway cough syndrome (UACS) / post-nasal drip syndrome** — Chronic nasal or sinus inflammation produces persistent secretions that irritate the pharynx and larynx. 2. **Asthma / cough-variant asthma** — Chronic airway inflammation with eosinophilic infiltration and bronchial hyperresponsiveness. In cough-variant asthma, cough may be the sole presenting symptom without typical wheeze or dyspnea. 3. **Gastroesophageal reflux disease (GERD)** — Micro-aspiration of gastric acid or vagally mediated esophagobronchial reflex stimulates cough receptors. Notably, cough may occur without classic heartburn in up to 75 % of GERD-related cough cases. 4. **Non-asthmatic eosinophilic bronchitis (NAEB)** — Eosinophilic airway inflammation without the bronchial hyperresponsiveness seen in asthma. 5. **ACE inhibitor–induced cough** — Accumulation of bradykinin and substance P in the airways due to inhibition of angiotensin-converting enzyme. Affects 5–20 % of patients on ACE inhibitors and may develop weeks to months after initiation [4]. 6. **Chronic bronchitis (COPD)** — Chronic inflammation of bronchial mucosa, typically from cigarette smoke, leads to goblet cell hyperplasia, mucus hypersecretion, and impaired mucociliary clearance. 7. **Post-infectious cough** — Residual airway inflammation and transient bronchial hyperreactivity following a respiratory infection. May persist 3–8 weeks or longer. 8. **Bronchiectasis** — Permanent dilation of bronchi with chronic infection and impaired clearance of secretions. 9. **Lung malignancy** — Endobronchial tumors or mediastinal masses irritate airway receptors. Usually accompanied by other symptoms such as hemoptysis, weight loss, or chest pain. --- ## RED FLAGS The following signs or symptom combinations associated with cough warrant **immediate medical attention** (emergency department or call emergency services): - **Massive hemoptysis** — coughing up large volumes of blood (generally > 100 mL in 24 hours) or any amount causing respiratory compromise - **Severe respiratory distress** — marked dyspnea at rest, use of accessory muscles, inability to speak in full sentences, cyanosis, or oxygen saturation < 92 % - **Stridor** — high-pitched inspiratory sound suggesting upper-airway obstruction (potential foreign body, anaphylaxis, or epiglottitis) - **Chest pain** with hemodynamic instability — may indicate pulmonary embolism, tension pneumothorax, or acute cardiac event - **Suspected foreign-body aspiration** — sudden-onset cough with choking, especially in children or elderly - **High fever (≥ 39.5 °C / 103 °F) with rigors and productive cough** — concerning for severe pneumonia or sepsis - **Signs of anaphylaxis** — cough with urticaria, angioedema, wheezing, hypotension after exposure to a known or potential allergen - **Cough with new-onset confusion or altered consciousness** — may indicate hypoxia, sepsis, or neurological emergency - **Immunocompromised patient with worsening cough and fever** — risk for opportunistic infections requiring urgent workup --- ## Self-Care at Home For acute cough associated with viral URTIs, the following non-pharmacological measures have varying degrees of evidence and are generally considered safe: 1. **Adequate hydration** — Maintaining fluid intake may help thin secretions and soothe irritated mucous membranes. While direct trial evidence is limited, this recommendation is supported by expert consensus in multiple clinical guidelines [4]. 2. **Honey (1–2 tablespoons before bedtime)** — A Cochrane systematic review found that honey may be superior to no treatment and diphenhydramine, and comparable to dextromethorphan, in reducing cough frequency and severity in children over 1 year of age and adults [3]. **Do NOT give honey to children under 12 months** due to the risk of infant botulism. 3. **Humidified air** — Use of a cool-mist humidifier may ease cough related to dry indoor air. Clean the device regularly to prevent mold and bacterial growth. Evidence is largely anecdotal, but the intervention is low-risk. 4. **Nasal saline irrigation** — Isotonic or hypertonic saline rinses (e.g., neti pot, squeeze bottle) may reduce post-nasal drip and associated cough. A systematic review supports their use in acute and chronic rhinosinusitis [2]. 5. **Elevation of the head during sleep** — Sleeping with the upper body elevated approximately 15–20 cm may reduce nocturnal cough associated with GERD or post-nasal drip. 6. **Avoidance of irritants** — Eliminating exposure to tobacco smoke, strong odors, aerosols, and dust can reduce cough reflex stimulation. 7. **Throat lozenges and warm liquids** — Demulcent effects may temporarily soothe the pharynx and suppress the urge to cough. Warm liquids such as broth or herbal tea with honey may provide subjective relief. 8. **Steam inhalation** — Breathing steam from a bowl of hot water may help loosen congestion. Exercise caution to avoid burns. Evidence for efficacy is limited. --- ## OTC Medications That Help Over-the-counter cough preparations fall into several classes. A 2014 Cochrane review concluded that evidence for most OTC cough medications is limited, and benefits over placebo are modest at best for acute cough [3]. Nonetheless, certain agents may provide symptomatic relief in select patients. | Class | Example(s) | Typical Adult Dose | Notes | |---|---|---|---| | **Antitussive (centrally acting)** | Dextromethorphan (DXM) | 10–20 mg every 4 hours or 30 mg every 6–8 hours (max 120 mg/day) | Acts on sigma-1 and NMDA receptors in the brainstem cough center. Avoid with MAOIs and serotonergic drugs (serotonin syndrome risk). Modest evidence of efficacy over placebo [3]. | | **Expectorant** | Guaifenesin | 200–400 mg every 4 hours (max 2400 mg/day) | Proposed to thin mucus and improve mucociliary clearance. Evidence for clinical benefit is inconsistent. Generally well tolerated. | | **First-generation antihistamine** | Diphenhydramine, chlorpheniramine | Diphenhydramine 25 mg every 4–6 hours (max 150 mg/day) | May help cough related to post-nasal drip via anticholinergic drying effects. Causes drowsiness — may be beneficial at bedtime. Avoid in elderly due to anticholinergic burden. | | **Topical antitussive** | Menthol (lozenges, vapor rubs) | Per product label | Activates cold-sensitive TRPM8 receptors in the airway, producing a sensation of improved airflow. Evidence is limited but risk is minimal. | | **Decongestant (oral)** | Pseudoephedrine, phenylephrine | Pseudoephedrine 60 mg every 4–6 hours (max 240 mg/day) | Reduces nasal congestion that may contribute to post-nasal drip cough. Contraindicated in uncontrolled hypertension, severe coronary artery disease, and MAOIs. Phenylephrine oral bioavailability is very low; FDA advisory panel found it ineffective as oral decongestant. | | **Combination products** | DXM + guaifenesin; antihistamine + decongestant | Per product label | Widely marketed. Select products based on predominant symptoms. Avoid duplicating active ingredients when taking multiple products. | **Important:** Second-generation (non-sedating) antihistamines such as loratadine and cetirizine are generally **not** effective for cough associated with the common cold but may help cough caused by allergic rhinitis. --- ## Prescription Options Prescription cough therapy is reserved for cases where the underlying cause has been identified and targeted treatment is warranted, or when cough is refractory to OTC measures and significantly affects quality of life. | Class | Example(s) | Indication | Notes | |---|---|---|---| | **Inhaled corticosteroids (ICS)** | Fluticasone, budesonide, beclomethasone | Asthma, cough-variant asthma, eosinophilic bronchitis | First-line controller therapy for cough due to airway eosinophilia. Typically prescribed by GP or pulmonologist. Onset of benefit may take 2–8 weeks [2]. | | **Inhaled bronchodilators** | Albuterol (salbutamol), ipratropium | Asthma, COPD exacerbation | Albuterol relaxes bronchial smooth muscle (β2-agonist). Ipratropium (anticholinergic) may reduce mucus secretion and cough. | | **Proton pump inhibitors (PPIs)** | Omeprazole, esomeprazole, lansoprazole | GERD-related cough | 8–12 week trial at twice-daily dosing is generally recommended. Response may be slow (weeks to months). Prescribed by GP or gastroenterologist [4]. | | **Intranasal corticosteroids** | Fluticasone nasal spray, mometasone | UACS / chronic rhinosinusitis | Reduces mucosal inflammation and post-nasal secretions. First-line for UACS-associated chronic cough [1]. | | **Opioid antitussives** | Codeine, hydrocodone (in combination products) | Severe refractory cough | Suppress the medullary cough center. Risk of dependence, respiratory depression, and constipation. FDA restricts codeine use in patients under 18 years [5]. Use only when benefits clearly outweigh risks. | | **Gabapentin / pregabalin** | Gabapentin 300–1800 mg/day | Unexplained chronic cough (neurogenic / cough hypersensitivity) | Emerging evidence suggests neuromodulators may benefit refractory chronic cough by reducing cough reflex hypersensitivity. Used off-label. Generally prescribed by a specialist [2]. | | **Antibiotics** | Amoxicillin, doxycycline, azithromycin | Bacterial pneumonia, acute bacterial sinusitis, pertussis | Indicated ONLY when a bacterial cause is confirmed or strongly suspected. Inappropriate antibiotic use for viral cough contributes to antimicrobial resistance. | | **Gefapixant** | Gefapixant 45 mg twice daily | Refractory chronic cough in adults | P2X3 receptor antagonist approved for unexplained chronic cough or refractory chronic cough in adults. Common side effect: taste disturbance (dysgeusia). Prescribed by specialists [6]. | --- ## Lab Tests Typically Ordered The choice of investigations depends on the duration, character, and associated features of the cough. | Test | Rationale | When Ordered | |---|---|---| | **Chest X-ray** | Rules out pneumonia, lung mass, pleural effusion, heart failure, tuberculosis | Generally first-line imaging for any persistent or unexplained cough > 3 weeks, or acute cough with red-flag features | | **Complete blood count (CBC)** ([CBC](/tests/complete-blood-count)) | Elevated WBC suggests infection; eosinophilia may indicate allergic or eosinophilic etiology | Persistent cough with systemic symptoms | | **Spirometry with bronchodilator reversibility** | Assesses for obstructive airway disease (asthma, COPD) | Chronic cough, especially with wheeze or dyspnea | | **Fractional exhaled nitric oxide (FeNO)** | Elevated FeNO supports eosinophilic airway inflammation (asthma, NAEB) | Chronic cough when asthma or eosinophilic bronchitis is suspected | | **Methacholine challenge test** | Confirms bronchial hyperresponsiveness when spirometry is normal but asthma is suspected | Cough-variant asthma evaluation | | **Sputum culture and cytology** | Identifies bacterial pathogens; sputum eosinophils support NAEB; cytology screens for malignancy | Productive chronic cough, suspected TB, possible malignancy | | **CT chest (high-resolution)** | Detailed evaluation of lung parenchyma and airways — detects bronchiectasis, interstitial lung disease, small masses not seen on X-ray | Chronic cough with abnormal or inconclusive chest X-ray | | **24-hour esophageal pH / impedance monitoring** | Gold standard for diagnosing GERD-related cough | Chronic cough when GERD is suspected but empiric PPI trial has failed | | **Allergy testing (skin prick or specific IgE)** ([Allergy panel](/tests/allergy-panel)) | Identifies allergic triggers contributing to rhinitis and cough | Cough with clinical features of allergic rhinitis | | **Pertussis serology / PCR** | Confirms Bordetella pertussis infection | Subacute cough with paroxysmal quality, post-tussive vomiting, or known exposure | | **CT sinuses** | Evaluates chronic rhinosinusitis as cause of UACS | Chronic cough with nasal symptoms unresponsive to empiric therapy | --- ## Special Populations ### Children Cough in children is extremely common, with the average healthy child experiencing 5–8 viral URTIs per year. Key considerations: - **Children under 2 years:** The FDA and American Academy of Pediatrics strongly advise **against** use of any OTC cough and cold products in children younger than 2 years due to lack of proven efficacy and risk of serious adverse effects [5]. - **Children 2–6 years:** OTC cough medications should be used with caution and only under the guidance of a healthcare provider. Evidence for efficacy in this age group is lacking [3]. - **Honey** may be considered for children **over 12 months** — studies suggest 2.5–5 mL of honey before bedtime may reduce nocturnal cough [3]. **Never give honey to infants under 1 year** (botulism risk). - **Codeine is contraindicated in children under 18 years** for cough per FDA guidance due to the risk of ultra-rapid CYP2D6 metabolism leading to fatal respiratory depression [5]. - **Pediatric-specific causes** to consider: foreign body aspiration (especially ages 1–3), croup (barking cough with stridor), pertussis (especially in under- or unvaccinated children), and protracted bacterial bronchitis. - **Persistent cough in children > 4 weeks** should be evaluated by a pediatrician to rule out asthma, protracted bacterial bronchitis, and less common causes such as cystic fibrosis or primary ciliary dyskinesia. ### Pregnancy Cough during pregnancy requires careful medication selection: - **Non-pharmacological measures** (honey, humidification, saline irrigation, hydration) are first-line and generally considered safe. - **Dextromethorphan** — Generally considered compatible with pregnancy (no clear teratogenic signal in human data). However, prolonged or high-dose use should be avoided, and patients should consult their obstetrician or midwife. - **Guaifenesin** — Limited human data; generally regarded as low risk, but use should be discussed with a clinician. - **Antihistamines** — Chlorpheniramine and diphenhydramine have extensive human pregnancy data and are generally considered acceptable when benefits outweigh risks. Consult ACOG guidance [7]. - **Pseudoephedrine** — Some epidemiological studies have reported a small increased risk of gastroschisis with first-trimester use. Avoid in the first trimester; use with caution thereafter. - **Codeine and opioid antitussives** — Associated with neonatal withdrawal syndrome and potential (though debated) teratogenic risk. Generally avoided unless absolutely necessary. - **ACE inhibitors** (a common cause of chronic cough) are **contraindicated throughout pregnancy** due to fetotoxicity. Women who become pregnant on an ACE inhibitor should have their medication switched promptly. - ACOG recommends that pregnant patients experiencing persistent cough be evaluated for underlying causes (asthma, GERD, infection) and managed in consultation with their obstetric provider [7]. ### Elderly - **Decreased cough reflex sensitivity** — Older adults may have a diminished cough reflex, increasing the risk of silent aspiration and aspiration pneumonia. - **Anticholinergic burden** — First-generation antihistamines (diphenhydramine) should be avoided or used with extreme caution in the elderly per the American Geriatrics Society Beers Criteria. Risks include confusion, urinary retention, falls, and cognitive impairment. - **Polypharmacy** — Always review the medication list. ACE inhibitor–induced cough is common and may be resolved by switching to an angiotensin II receptor blocker (ARB). - **Underlying comorbidities** — Cough in the elderly is more likely to represent serious pathology (heart failure, malignancy, COPD, tuberculosis). A lower threshold for investigation is warranted. - **Decongestant caution** — Pseudoephedrine can raise blood pressure and should be used cautiously in elderly patients with hypertension or cardiovascular disease. ### Athletes - **Exercise-induced bronchoconstriction (EIB)** is a common cause of cough during or after exertion in athletes. Prevalence is particularly high in endurance and cold-weather sports (cross-country skiing, swimming). - Diagnosis typically requires an exercise challenge test or eucapnic voluntary hyperventilation test. - Treatment generally involves pre-exercise use of a short-acting beta-agonist (e.g., salbutamol) and, in persistent cases, regular inhaled corticosteroids. - Athletes should be aware of **anti-doping regulations** — certain medications require a Therapeutic Use Exemption (TUE). Consult the World Anti-Doping Agency (WADA) Prohibited List. - **Environmental triggers** — Athletes training in polluted environments, chlorinated pools, or cold air may experience irritant-related cough that resolves with environmental modification. --- ## When to Escalate Use the following guidance to determine the appropriate level of care. When in doubt, err on the side of seeking medical evaluation sooner. ### Same-Day GP / Primary Care Visit - Cough lasting more than 3 weeks without improvement - Productive cough with discolored (green or yellow) sputum persisting beyond 10 days - Cough accompanied by low-grade fever (< 39 °C) for more than 5 days - Cough with new-onset wheezing or exertional dyspnea - Suspicion that a current medication (e.g., ACE inhibitor) may be causing the cough - Cough disrupting sleep or daily functioning despite appropriate self-care ### Urgent Care (Same Day or Within 24 Hours) - Cough with moderate dyspnea not relieved by rest or rescue inhaler - Cough with blood-streaked sputum (small-volume hemoptysis) - High fever (≥ 38.5 °C) with productive cough and malaise suggestive of pneumonia - Worsening cough in a patient with known COPD, heart failure, or immunocompromise - Cough with unilateral chest pain or pleurisy ### Emergency Department / Call Emergency Services (911) - Severe respiratory distress (see Red Flags section above) - Massive hemoptysis - Suspected foreign-body aspiration with ongoing respiratory compromise - Cough with signs of anaphylaxis - Cough with hemodynamic instability (hypotension, tachycardia, altered consciousness) - Cough with acute-onset severe chest pain — possible pulmonary embolism or pneumothorax --- ## References [1] Irwin RS, French CL, Chang AB, Altman KW; CHEST Expert Cough Panel. Classification of Cough as a Symptom in Adults and Management Algorithms: CHEST Guideline and Expert Panel Report. *Chest*. 2018;153(1):196-209. PMID:29080708. [2] Morice AH, Millqvist E, Bieksiene K, et al. ERS guidelines on the diagnosis and treatment of chronic cough in adults and children. *Eur Respir J*. 2020;55(1):1901136. PMID:31515408. [3] Smith SM, Schroeder K, Fahey T. Over-the-counter (OTC) medications for acute cough in children and adults in community settings. *Cochrane Database Syst Rev*. 2014;(11):CD001831. PMID:25420096. [4] Morice AH, McGarvey L, Pavord I; British Thoracic Society Cough Guideline Group. Recommendations for the management of cough in adults. *Thorax*. 2006;61 Suppl 1:i1-i24. PMID:16936235. [5] U.S. Food and Drug Administration. FDA Drug Safety Communication: FDA restricts use of prescription codeine pain and cough medicines and tramadol pain medicines in children; recommends against use in breastfeeding women. April 2017; updated 2018. Available at: https://www.fda.gov/drugs/drug-safety-and-availability. [6] European Medicines Agency. Lyfnua (gefapixant) — EPAR summary for the public. 2022. Available at: https://www.ema.europa.eu. [7] American College of Obstetricians and Gynecologists (ACOG). Committee Opinion No. 721: Smoking Cessation During Pregnancy; and guidance on medication use during pregnancy and lactation. *Obstet Gynecol*. 2017. [8] National Institute for Health and Care Excellence (NICE). Cough (acute): antimicrobial prescribing. NICE guideline [NG120]. 2019. Available at: https://www.nice.org.uk/guidance/ng120. [9] Chang AB, Oppenheimer JJ, Irwin RS; CHEST Expert Cough Panel. Managing Chronic Cough as a Symptom in Children and Management Algorithms: CHEST Guideline and Expert Panel Report. *Chest*. 2020;158(1):303-329. PMID:32026921. --- *This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional for diagnosis and treatment of any medical condition. Content reviewed by the PillsCard Medical Editorial Board.*