Childhood Asthma — Causes, Triggers, Symptoms & Inhaler Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Asthma in children is a chronic inflammatory disease of the airways characterised by variable and reversible airflow obstruction, bronchial hyperresponsiveness, and airway remodelling. It is the most common chronic condition in childhood, affecting approximately 339 million people globally and 1 in 11 children in the UK. Asthma in children involves eosinophilic airway inflammation triggered by exposure to allergens and viral infections, causing episodic bronchoconstriction, mucus hypersecretion, and airway oedema. Unlike in adults, childhood asthma often has an allergic ('atopic') basis — associated with atopic dermatitis, allergic rhinitis, and food allergy (the 'atopic march'). The condition varies from intermittent, mild episodes to severe, poorly controlled disease requiring daily preventive therapy. Many children experience significant improvement or resolution of asthma by adulthood, though persistent asthma continues into adult life in 30–50% of cases.

Genetic predisposition: family history of asthma, atopic dermatitis, or allergic rhinitis significantly increases risk — heritability is estimated at 60–80%. Allergen sensitisation: house dust mite (Dermatophagoides pteronyssinus and D. farinae), cat and dog dander, cockroach allergen, moulds (Alternaria, Aspergillus), and grass and tree pollens are the major indoor and outdoor allergens driving atopic asthma. Respiratory viral infections (rhinovirus — responsible for 60–80% of asthma exacerbations; RSV in infants) are the primary trigger for acute episodes. Risk factors: maternal smoking during pregnancy, childhood tobacco smoke exposure (passive smoking), air pollution (nitrogen dioxide, PM2.5, diesel particulates), prematurity, formula feeding (versus breastfeeding), obesity, low birth weight, and early antibiotic use (dysbiosis hypothesis). Exercise is a common trigger (exercise-induced bronchoconstriction) and cold dry air provokes symptoms.

Classic triad: episodic wheeze (high-pitched expiratory whistle), dry cough (often nocturnal and early morning — a key diagnostic feature in children), and breathlessness with a sensation of chest tightness. Symptoms are variable and characteristically reversible — improved spontaneously or with bronchodilators. In infants and young children (where spirometry is not possible), recurrent wheeze episodes in the context of a personal or family atopy history are used for clinical diagnosis. Signs of severe/life-threatening acute asthma: increased respiratory rate, use of accessory muscles (intercostal and suprasternal recession, head-bobbing in infants), nasal flaring, SpO2 below 94% on air, peak flow below 33–50% of predicted, silent chest (absence of wheeze in severe obstruction — inability to move sufficient air), cyanosis, poor feeding in infants, and inability to speak full sentences. Exercise-induced asthma: cough, wheeze, and breathlessness 5–15 minutes after exercise onset.

Asthma in children is a clinical diagnosis based on the characteristic pattern of episodic symptoms, trigger history, response to bronchodilators, and exclusion of alternative diagnoses. In children over 5 years: spirometry demonstrating reversible obstructive pattern (FEV1/FVC below 0.70, FEV1 improvement above 12% or 200 mL after salbutamol); peak expiratory flow (PEF) variability above 20% diurnally or with treatment. Fractional exhaled nitric oxide (FeNO): elevated above 35 ppb supports eosinophilic airway inflammation. Allergy testing: skin prick tests or specific IgE serology (RAST) to identify allergen sensitisation (house dust mite, pollen, pet dander, moulds). Chest X-ray: hyperinflation in acute asthma; excludes pneumonia, foreign body, or congenital abnormality. In children under 5: the Childhood Asthma Control Test (C-ACT) and a trial of inhaled corticosteroids with reassessment at 4–8 weeks are used to support diagnosis. Differential diagnoses: croup, bronchiolitis, inhaled foreign body, vocal cord dysfunction, and cardiac disease must be excluded.

Stepwise management according to GINA and NICE guidelines. Reliever therapy: short-acting beta-2 agonist (SABA) — salbutamol (Ventolin) 100–200 mcg via metered-dose inhaler (MDI) + spacer; immediate bronchodilation for acute symptoms. Children under 5 use MDI + spacer; older children may use MDI + spacer or dry powder inhaler (DPI). Preventer therapy: low-dose inhaled corticosteroid (ICS) — beclomethasone 100–200 mcg/day, fluticasone 50–100 mcg/day, or budesonide 200–400 mcg/day — the most effective preventer; taken daily regardless of symptoms. Step-up therapy: add leukotriene receptor antagonist (montelukast 4–5 mg under 6 years, 5 mg 6–14 years); increase ICS dose; add long-acting beta-2 agonist (LABA — salmeterol, formoterol) in children over 5. Acute asthma exacerbation management in hospital: continuous salbutamol nebulisation, ipratropium bromide nebulisation, oral or IV prednisolone (1–2 mg/kg/day for 3–5 days), supplemental oxygen to maintain SpO2 94–98%, IV magnesium sulfate for severe exacerbations. Allergen immunotherapy (subcutaneous or sublingual) for specific allergen-sensitised asthma. Biologics (mepolizumab, dupilumab) for severe refractory eosinophilic asthma in children over 6 years.

Uncontrolled or under-treated childhood asthma causes severe acute attacks requiring hospitalisation, life-threatening status asthmaticus (requiring intensive care), and asthma deaths — most considered preventable with appropriate preventer therapy. Chronic poorly controlled asthma drives airway remodelling — subepithelial fibrosis, smooth muscle hypertrophy, and irreversible structural changes causing persistent airflow limitation into adulthood. Children with uncontrolled asthma achieve a lower peak lung function in young adulthood, increasing long-term respiratory morbidity. School absence, restriction of physical activity, and sleep disruption from nocturnal symptoms significantly impair educational achievement, physical fitness, and overall quality of life. Psychological comorbidities — anxiety and depression — affect 25-40% of children with severe asthma.

Every child with asthma should have a personalised written Asthma Action Plan detailing daily medication, trigger avoidance, how to recognise worsening, and what to do in an emergency. Peak flow monitoring: children over 5 should use a peak flow meter to monitor asthma control — record twice daily for 2–4 weeks to establish personal best. Trigger avoidance: house dust mite reduction measures (allergen-proof mattress and pillow encasings, vacuum with HEPA filter, reduce soft toys, maintain low indoor humidity); strict no-smoking environment; manage allergic rhinitis (the 'one airway' concept — treating rhinitis improves asthma control); avoid aspirin and NSAIDs in aspirin-sensitive asthma; annual influenza vaccination. Exercise: children with controlled asthma should be fully active — pre-exercise SABA (salbutamol 200 mcg 15 minutes before) prevents exercise-induced bronchoconstriction. Ensure correct inhaler technique is demonstrated and checked at every clinical review.

Call emergency services immediately (999/112/911) for: a child with severe breathing difficulty, cannot speak full sentences, SpO2 below 92%, blue lips or fingernails, exhaustion, silent chest, or no improvement after 4–6 puffs of salbutamol through a spacer repeated twice at 20-minute intervals. Take your child to the GP or paediatric unit urgently for: their first episode of wheeze, recurrent nighttime cough, worsening asthma control despite preventer therapy, or suspected new allergen exposure. Schedule a routine review if peak flow is consistently below 80% of personal best, reliever inhaler is needed more than 3 times per week, or waking from asthma more than once per week. All children with asthma should have an annual asthma review with their GP or nurse.