Children's Cough: When to Wait, and When to Investigate

Cough is the most common reason children see a doctor — more than 75% of children with troublesome coughs visit a clinic five or more times a year. Yet most childhood coughs are protective reflexes that clear the airway and need observation rather than medication. China's 2021 clinical practice guideline for children's cough distils the evidence into a calm, stepwise approach; this guide translates its key points for parents.

First, classify: how long and how wet

Coughs are classified by duration — acute (under 2 weeks), persistent (2–4 weeks) and chronic (over 4 weeks) — and by whether they are dry or wet (producing phlegm). Most acute coughs follow viral respiratory infections and get better on their own. Studies cited in the guideline show that more than half of children still cough ten days after an ordinary respiratory infection, and about one in ten is still coughing after 25 days — a normal tail-off that often needs nothing more than patience. Young children typically have six to eight colds a year.

Why more medicine is not better

The guideline is unusually firm here. Antibiotics are not routinely recommended for acute cough (strong recommendation, high-quality evidence): they do not shorten viral illness and increase resistance and side effects. Over-the-counter cough suppressants such as dextromethorphan perform no better than honey, and codeine-based products carry real risks in children. Mucolytics are not routinely recommended — several countries restrict them below age two or six. Antihistamines and decongestants do not help ordinary acute coughs. Honey (for children over one year), fluids and a smoke-free environment are the evidence-based basics.

The three usual suspects in chronic cough

For coughs beyond four weeks, China-wide studies identify three leading causes: cough-variant asthma (about 42%), upper airway cough syndrome — post-nasal drip from allergic or chronic rhinitis (about 25%) — and post-infection cough (about 22%). Age matters: below six years, post-infection cough is common and in infants doctors stay alert to inhaled foreign bodies (half of airway-foreign-body cases occur before the first birthday). From age six, allergic causes dominate, and psychological ("habit") cough appears more often in school-age children — it typically vanishes during sleep and responds to reassurance, not medication.

Which tests are worth doing

For chronic cough, a chest X-ray is the recommended first test. CT is reserved for when the X-ray cannot explain the cough, or when specific warning signs appear — for example clubbing of the fingers, or suspicion of an inhaled object. Children six and older should have lung-function (spirometry) testing. A fractional exhaled nitric oxide (FeNO) test helps when cough-variant asthma is suspected. Allergy testing is not routine — it is used only when allergy is genuinely suspected. Bronchoscopy comes last, when non-invasive workup fails, when wet cough has not improved after four weeks of appropriate antibiotics, or when an airway abnormality is suspected.

Medicines that do help, when indicated

When a bacterial cause is genuinely suspected, first-line treatment is oral amoxicillin or amoxicillin–clavulanate for 5–7 days. For chronic wet cough — often protracted bacterial bronchitis in under-fives — amoxicillin–clavulanate for at least two weeks is evidence-based. A suspected cough-variant asthma trial uses inhaled bronchodilators (a good response supports the diagnosis). For non-specific chronic cough, a 2–4 week trial of inhaled corticosteroid followed by formal reassessment is reasonable; leukotriene antagonists and anti-reflux medicines are not recommended routinely. For allergic upper airway cough, a second-generation antihistamine such as cetirizine or loratadine treats the cause.

When to seek a specialist

If two or more weeks of treatment from a general paediatrician has not helped, if cough recurs in a repeating pattern, or if any red flag appears — breathing difficulty, poor weight gain, coughing blood, chronic wet cough with fever — ask for referral to a paediatric respiratory specialist. And one measure helps more than any medicine: keeping the child away from second-hand smoke. Around half of children in households where both parents smoke have recurring cough.