What is asthma?
Asthma is a chronic inflammatory disease of the airways characterised by three hallmarks: airway inflammation, bronchospasm (tightening of airway smooth muscle), and airway hyperresponsiveness (an exaggerated reaction to triggers that wouldn't affect most people). These three elements interact to cause episodes of wheezing, breathlessness, chest tightness, and cough — especially at night or early morning.
What makes asthma complex is its heterogeneity. "Asthma" is not a single disease but an umbrella of overlapping conditions with different underlying mechanisms (endotypes), different triggers, and therefore different optimal treatments. This is why a personalised approach guided by specialist assessment produces far better outcomes than one-size-fits-all management.
Types of asthma
| Type | Features | Key biomarkers |
|---|---|---|
| Allergic (atopic) | Most common; triggered by allergens; often associated with eczema and hay fever; onset usually childhood; responds well to ICS | High IgE; eosinophils; positive skin prick tests |
| Non-allergic | Adult onset common; triggers include infections, irritants, cold air; lower IgE; may be more difficult to control | Normal IgE; variable eosinophils |
| Eosinophilic | High eosinophil count; often severe; late-onset; responds to anti-IL-5 biologics | Blood eos >300 cells/μL; sputum eos; high FeNO |
| Exercise-induced (EIB) | Symptoms triggered by physical activity; cold/dry air exacerbates; common in elite athletes | Post-exercise spirometry; eucapnic voluntary hyperpnoea test |
| Occupational | Triggered by workplace exposures — isocyanates, flour, latex, animal proteins; improvement off work | Serial peak flow at/away from work; specific IgE to occupational allergens |
| Aspirin-exacerbated respiratory disease (AERD) | Triad: asthma + nasal polyps + aspirin/NSAID sensitivity; often severe | Clinical diagnosis; aspirin challenge under supervision |
Common triggers
Identifying and avoiding individual triggers is a cornerstone of asthma management. Triggers vary significantly between patients — keeping a symptom diary helps identify patterns.
🌿 Allergens
- House dust mite (most common)
- Pet dander (cat > dog)
- Mould/damp environments
- Tree, grass, and weed pollen
- Cockroach allergen
🌬️ Respiratory
- Viral upper respiratory infections
- Cold, dry air
- Air pollution and ozone
- Tobacco smoke (active & passive)
- Occupational exposures
💊 Medications
- Aspirin and NSAIDs (AERD)
- Beta-blockers (all routes)
- ACE inhibitors (cough, not asthma)
- Some eye drops (timolol)
🏃 Other
- Exercise (especially cold air)
- Strong emotional stress
- GORD/reflux
- Hormonal changes (menstrual cycle)
- Food additives (sulphites, tartrazine)
Symptoms and diagnosis
The classic symptom quartet is: wheeze, breathlessness, chest tightness, and cough — worse at night or early morning, variable in nature, and triggered by known precipitants. Variable airflow limitation is confirmed by spirometry.
Reliever inhaler not working after 15 minutes · Difficulty completing sentences · Respiratory rate >25/min · Heart rate >110/min · Oxygen saturation <92% · Blue lips or fingertips (cyanosis) · Silent chest (wheeze has disappeared — very dangerous sign)
Diagnostic tests
- Spirometry with bronchodilator reversibility: FEV1/FVC <0.7 with ≥12% and ≥200 mL improvement after salbutamol confirms obstruction and reversibility.
- Peak expiratory flow (PEF) variability: >10% diurnal variability over 2 weeks is consistent with asthma.
- FeNO (fractional exhaled nitric oxide): Measures eosinophilic airway inflammation. >50 ppb strongly suggests eosinophilic asthma and predicts ICS responsiveness.
- Bronchial challenge test: Methacholine or mannitol challenge for borderline cases — a negative test effectively excludes asthma.
Inhalers explained
| Class | Examples | Onset | Role | Key point |
|---|---|---|---|---|
| SABA (reliever) | Salbutamol, Albuterol, Terbutaline | 2–5 min | Acute symptom relief | Frequent use (>2×/week) signals poor control — step up preventer therapy |
| ICS (preventer) | Budesonide, Fluticasone propionate, Beclometasone, Ciclesonide | Days–weeks | Daily controller — reduces inflammation | Cornerstone of asthma management at all steps; rinse mouth after use |
| ICS/LABA (combination) | Budesonide/formoterol (Symbicort), Fluticasone/salmeterol (Seretide/Advair), Fluticasone/vilanterol (Relvar) | ICS: days; LABA: 1–3 min (formoterol) | Maintenance — Step 3+ | Never use LABA without ICS; SMART strategy uses ICS/formoterol as both maintenance and reliever |
| LAMA (anticholinergic) | Tiotropium (Spiriva Respimat) | 30 min | Add-on therapy — Step 4+ | Most evidence in severe asthma; reduces exacerbations ~21%; well-tolerated |
| LTRA | Montelukast (Singulair) | Days | Add-on or mild persistent | Particularly useful in aspirin-exacerbated and exercise-induced asthma; neuropsychiatric warning (FDA) |
| Oral corticosteroids (OCS) | Prednisolone | Hours | Rescue courses for exacerbations | Short courses (5–7 days) safe; chronic use causes significant adverse effects — biologics aim to eliminate OCS dependence |
GINA now recommends the SMART approach (Single Maintenance And Reliever Therapy) as the preferred strategy from Step 3: patients use their ICS/formoterol combination inhaler as both their daily maintenance therapy and as their as-needed reliever, replacing the traditional SABA reliever. This approach reduces severe exacerbations by 30–50% compared to conventional therapy, because every reliever dose automatically delivers anti-inflammatory medication alongside bronchodilation.
GINA stepwise treatment
The Global Initiative for Asthma (GINA) recommends a stepwise approach where treatment is stepped up if symptoms are uncontrolled and stepped down once control is achieved for 3+ months. Assessment should occur every 3–6 months.
| Step | Preferred controller | Preferred reliever | Severity |
|---|---|---|---|
| Step 1 | Low-dose ICS/formoterol as needed | ICS/formoterol as needed (SMART) | Mild intermittent |
| Step 2 | Low-dose ICS daily | ICS/formoterol as needed (SMART) | Mild persistent |
| Step 3 | Low-dose ICS/LABA daily | ICS/formoterol as needed (SMART) | Moderate persistent |
| Step 4 | Medium-dose ICS/LABA ± tiotropium | ICS/formoterol as needed (SMART) | Severe |
| Step 5 | High-dose ICS/LABA + biologic therapy | ICS/formoterol as needed | Very severe / uncontrolled |
Biologic therapies for severe asthma
Biologics are injectable monoclonal antibodies targeting specific inflammatory pathways. They are transformative for patients with severe uncontrolled asthma — typically reducing exacerbations by 50–70% and eliminating the need for daily oral steroids in many patients. Choosing the right biologic requires knowing the patient's inflammatory phenotype.
| Biologic | Target | Key eligibility | Dosing | Exacerbation reduction |
|---|---|---|---|---|
| Omalizumab (Xolair) | Anti-IgE | Allergic asthma; IgE 30–1,500 IU/mL; skin-test positive | 2–4 weekly SC (weight/IgE-based) | ~25% |
| Mepolizumab (Nucala) | Anti-IL-5 | Eosinophilic asthma; blood eos ≥150 cells/μL at initiation | 100 mg monthly SC | ~50% |
| Reslizumab (Cinqair) | Anti-IL-5 | Eosinophilic asthma; blood eos ≥400 cells/μL; weight-based | 3 mg/kg monthly IV | ~50% |
| Benralizumab (Fasenra) | Anti-IL-5Rα | Eosinophilic; eos ≥300 cells/μL; directly depletes eosinophils | 30 mg SC — monthly ×3, then 8-weekly | ~51% |
| Dupilumab (Dupixent) | Anti-IL-4/IL-13 (IL-4Rα) | Moderate–severe asthma; eos ≥150 or FeNO ≥25; also treats AD and CRSwNP | 200–300 mg 2-weekly SC | ~70% |
| Tezepelumab (Tezspire) | Anti-TSLP | Severe uncontrolled asthma regardless of eosinophil count — broadest eligibility | 210 mg monthly SC | ~70% (all comers) |
Asthma action plan
Every person with asthma should have a written asthma action plan specifying what to do in three zones — based on peak flow or symptoms:
- Green zone (>80% personal best PEF): Take medications as usual. No symptoms. Continue regular activities.
- Yellow zone (50–79% PEF): Use reliever inhaler. If no improvement in 15–20 minutes, repeat and contact doctor. Start prednisolone if prescribed.
- Red zone (<50% PEF or severe symptoms): Use reliever inhaler. Call 911 / go to ER immediately if no rapid improvement.
Frequently asked questions
There is currently no cure for asthma. However, with appropriate treatment — particularly inhaled corticosteroids as daily preventer therapy — most people achieve excellent symptom control and live fully active lives. Some children appear to outgrow asthma, though underlying airway hyperresponsiveness often persists into adulthood, and symptoms may return during viral infections, pregnancy, or with occupational exposures.
Reliever inhalers (SABAs like salbutamol) work within minutes by relaxing airway smooth muscle — they treat the symptom but not the underlying inflammation. Preventer inhalers (ICS) contain corticosteroids that reduce airway inflammation when taken daily — they have no immediate bronchodilator effect but significantly reduce attack frequency and severity over time. Many patients only use their blue reliever and neglect the preventer — this is the most common reason for poor asthma control.
Biologic therapies are injectable monoclonal antibodies targeting specific inflammatory molecules — IgE, IL-5, IL-4/IL-13, or TSLP. They are indicated for severe uncontrolled asthma (GINA Step 5) despite optimal inhaled therapy — typically defined as two or more exacerbations per year requiring oral steroids, or continuous oral steroid dependence. Eligibility and biologic choice depend on blood eosinophil count, IgE level, allergy testing, and FeNO measurement.
- Global Initiative for Asthma. GINA Report 2024: Global Strategy for Asthma Management and Prevention. ginasthma.org
- Papi A, et al. Budesonide–formoterol as maintenance and reliever treatment in patients with asthma (PRACTICAL). Lancet. 2018;392(10165):2633–2642.
- Rabe KF, et al. Budesonide and formoterol in a single inhaler for maintenance and relief in mild-to-moderate asthma. NEJM. 2006;355(23):2378–2391.
- Menzies-Gow A, et al. Tezepelumab in Adults and Adolescents with Severe, Uncontrolled Asthma (NAVIGATOR). NEJM. 2021;384(19):1800–1809.
- Castro M, et al. Dupilumab Efficacy and Safety in Moderate-to-Severe Uncontrolled Asthma (LIBERTY ASTHMA QUEST). NEJM. 2018;378(26):2486–2496.