What is asthma?
Asthma is a chronic inflammatory disease of the airways characterised by three overlapping problems: airway inflammation, bronchospasm (tightening of the smooth muscle surrounding the airways), and mucus hypersecretion. Together, these cause the familiar symptoms of wheeze, cough, chest tightness, and shortness of breath — which typically vary over time and in response to specific triggers.
The fundamental abnormality is airway hyperresponsiveness — asthmatic airways are exquisitely sensitive to a wide range of stimuli that would have little or no effect on normal airways. When exposed to a trigger (allergen, cold air, exercise, viral infection), the asthmatic airway mounts an exaggerated inflammatory and bronchospastic response that can narrow the airway by 50% or more within minutes.
Asthma is episodic — symptoms fluctuate. Between episodes, many people feel completely normal and have normal lung function. This variability is actually one of the diagnostic hallmarks of asthma, distinguishing it from other obstructive lung diseases like COPD, where airflow limitation is persistent and largely irreversible.
Both asthma and COPD cause airflow obstruction, but they differ fundamentally. Asthma typically begins in childhood or young adulthood, is largely reversible with bronchodilators, has variable symptoms, and is driven by allergic/inflammatory mechanisms. COPD usually develops after age 40, is predominantly caused by smoking, shows only partial reversibility, and involves permanent structural lung damage (emphysema and chronic bronchitis). Some patients have features of both — a condition called ACOS (Asthma-COPD Overlap Syndrome) — which requires specialised management.
Types of asthma
🌿 Allergic (Atopic)
- Most common type (~60%)
- IgE-mediated hypersensitivity
- Triggered by allergens (dust, pollen, pets)
- Often with eczema/hay fever (atopic triad)
- Excellent response to ICS therapy
- Biologic therapy (anti-IgE) very effective
🌬️ Non-Allergic
- Not driven by allergy/IgE
- Triggered by infections, irritants, cold air, stress
- Often adult onset
- Normal IgE; negative skin prick tests
- May be harder to control
- Anti-IL-5 biologics may help if eosinophilic
🏃 Exercise-Induced (EIB)
- Triggered by physical exertion
- Peak symptoms 5–15 min post-exercise
- Caused by airway cooling and drying
- Common in elite athletes
- Pre-exercise SABA prevents attacks
- Nasal breathing during exercise helps
🏭 Occupational
- Caused by workplace exposures
- 200+ known occupational sensitisers
- Bakers, healthcare workers, painters at risk
- Symptoms improve on days off/holidays
- Early removal from exposure is critical
- Can become permanent if exposure continues
🔴 Severe / Refractory
- Uncontrolled on high-dose ICS + LABA
- ~5–10% of all asthma patients
- Requires specialist care
- Biologic therapy is transforming outcomes
- High exacerbation and hospitalisation burden
- Frequent OCS use causes serious side effects
🔗 ACOS
- Asthma-COPD Overlap Syndrome
- Features of both conditions
- Typically older patients with smoking history
- Partially reversible obstruction
- Worse outcomes than either alone
- ICS essential; LABA + LAMA often needed
Symptoms and attack warning signs
The classic asthma symptom quartet is: wheeze (a high-pitched whistling sound during breathing, especially exhalation), cough (often worse at night or early morning), chest tightness (a sensation of pressure or constriction), and shortness of breath. Not all patients have all four — some have predominantly cough (cough-variant asthma), others predominantly wheeze or breathlessness.
| Severity | Symptoms | Breathing | Peak flow | Action |
|---|---|---|---|---|
| Mild | Mild wheeze, cough; can complete sentences | Slightly increased rate | ≥80% of personal best | Use reliever inhaler; monitor |
| Moderate | Wheeze, breathlessness; sentences difficult | Rate increased; accessory muscles | 50–80% of personal best | Reliever + contact doctor; consider OCS |
| Severe | Unable to complete words; distressed | Marked increase; hunched forward | <50% of personal best | Call 999/911 immediately; nebulised bronchodilator |
| Life-threatening | Silent chest (no wheeze — air movement too poor); cyanosis; exhaustion; confusion | Paradoxical breathing; severe hypoxia | <33% of personal best | Emergency 911 — ICU admission likely needed |
Reliever inhaler gives no relief after 10 puffs · Lips or fingertips turning blue (cyanosis) · Breathing too difficult to speak · Chest/neck muscles visibly straining with each breath · Feeling of impending doom · Silent chest (wheeze disappears — this means near-complete airflow obstruction)
Using reliever inhaler more than twice per week · Waking at night with asthma more than twice per month · Symptoms limiting daily activities · Any asthma attack in the past year
Common asthma triggers
| Trigger category | Examples | Avoidance strategies |
|---|---|---|
| Allergens | House dust mites, pollen, pet dander (especially cats), mould spores, cockroach allergen | Allergen-proof mattress covers; HEPA air filtration; keep pets out of bedroom; monitor pollen counts; dehumidify to control mould |
| Respiratory infections | Rhinovirus (common cold), influenza, RSV, COVID-19 | Annual flu vaccination (strongly recommended); COVID vaccination; hand hygiene; have attack action plan ready |
| Exercise | Running, cycling — especially in cold, dry conditions | Pre-exercise SABA 15 min before; warm up gradually; breathe through nose; avoid exercising in high pollen/pollution; consider LTRA |
| Air pollutants | Cigarette smoke, diesel exhaust, ozone, particulate matter (PM2.5), wood-burning smoke | Never smoke or allow smoking indoors; check daily air quality index; avoid exercising near traffic on high-pollution days |
| Weather | Cold dry air, thunderstorms (thunderstorm asthma — sudden pollen fragmentation), high humidity | Cover mouth/nose in cold weather; check weather-related asthma alerts; carry reliever at all times |
| Irritants and fumes | Strong perfumes, cleaning products, paint fumes, cooking smoke, incense | Ventilate well when using products; choose fragrance-free alternatives; wear mask when painting |
| Medications | NSAIDs (aspirin, ibuprofen, naproxen) in ~10–20% of adults with asthma; beta-blockers (even eye drops) | Use paracetamol/acetaminophen instead of NSAIDs; always inform prescribers about asthma; avoid non-selective beta-blockers |
| Food and additives | Sulphites (wine, dried fruit, preserved foods); tartrazine; occasionally specific foods | Read food labels; avoid sulphite-containing foods if sensitive; true food-triggered asthma is less common than perceived |
| Emotions and stress | Strong emotional responses — laughing, crying, anxiety — alter breathing pattern and can trigger bronchospasm | Stress management; correct breathing technique; psychological support if anxiety co-exists |
| GORD / acid reflux | Gastro-oesophageal reflux disease causes microaspiration of acid which triggers airway inflammation | Treat reflux with PPIs; avoid large meals before bed; elevate head of bed |
Diagnosis and lung function tests
Asthma diagnosis is based on a pattern of characteristic symptoms plus objective evidence of variable airflow limitation. No single test is definitive — diagnosis integrates history, examination, and investigations.
Spirometry
The most important lung function test. You breathe into a machine that measures:
- FEV1 (Forced Expiratory Volume in 1 second): volume of air exhaled in the first second of a maximal forced breath
- FVC (Forced Vital Capacity): total air exhaled in a forced breath
- FEV1/FVC ratio: below 0.7 indicates airflow obstruction
A positive bronchodilator reversibility test — an increase in FEV1 of ≥12% and ≥200 mL after salbutamol — is strong evidence for asthma. Unlike COPD, asthma obstruction reverses significantly with bronchodilator.
Peak expiratory flow (PEF)
A simple, inexpensive bedside measurement using a peak flow meter — measures maximum speed of exhalation. In asthma, PEF is characteristically variable: lower in the morning ("morning dip"), lower during attacks, and improved by bronchodilators. A ≥20% diurnal variation in PEF over two weeks strongly supports asthma diagnosis. Peak flow monitoring is also central to asthma action plans.
Bronchial provocation testing
When spirometry is normal but asthma is suspected, provocation testing deliberately induces bronchoconstriction in a controlled setting using methacholine, histamine, or mannitol. A positive test confirms airway hyperresponsiveness. Particularly useful for diagnosing exercise-induced asthma and occupational asthma.
Fractional exhaled nitric oxide (FeNO)
FeNO measures nitric oxide in exhaled breath — a marker of eosinophilic (type 2) airway inflammation. A raised FeNO (≥40 ppb in adults) supports allergic/eosinophilic asthma and predicts a good response to inhaled corticosteroids and anti-IL-4/13 biologics. FeNO can also guide steroid dose adjustment and assess adherence.
Allergy testing
Skin prick testing or specific IgE blood tests identify allergen sensitisation in suspected allergic asthma. This guides allergen avoidance advice and suitability for allergen immunotherapy or anti-IgE biologic therapy (omalizumab).
Treatment: inhalers explained
Inhaled therapy is the cornerstone of asthma management — delivering medication directly to the airways in much lower doses than oral alternatives, minimising systemic side effects. Understanding the different inhaler types is essential for effective self-management.
Short-Acting Beta-2 Agonists (SABAs) — the "blue inhaler" — are the most commonly recognised asthma inhalers. They relax airway smooth muscle within 5–15 minutes, providing rapid symptom relief for up to 4–6 hours.
- Salbutamol / Albuterol (Ventolin): The universal reliever. Used for acute symptom relief and prevention of exercise-induced bronchospasm (taken 15 min before exercise).
- Levalbuterol (Xopenex): The active isomer of albuterol — may have slightly fewer side effects (tremor, palpitations) at equivalent bronchodilator doses.
- Terbutaline: Available as inhaler and subcutaneous injection for acute severe asthma.
This is the threshold for recommending preventer (ICS) therapy. Frequent reliever use means your asthma is inadequately controlled — see your doctor to step up treatment. Over-reliance on SABAs without preventer therapy is the leading cause of preventable asthma deaths.
SABA-free approach (GINA 2023): The latest GINA guidelines now recommend that even mild asthma patients should use a combination ICS/formoterol inhaler as their reliever (rather than SABA alone), since this simultaneously treats the underlying inflammation. This reduces exacerbation risk by up to 64% compared to SABA-only reliever. The preferred combination is budesonide/formoterol used as-needed.
Inhaled Corticosteroids (ICS) are the most effective preventer medications for asthma. They reduce airway inflammation, decrease hyperresponsiveness, reduce mucus production, and significantly reduce the risk of serious asthma attacks and asthma-related death. They must be taken daily — they do not provide immediate symptom relief.
| ICS | Brand | Dose equivalence | Notes |
|---|---|---|---|
| Beclometasone dipropionate (BDP) | Qvar, Clenil | Reference standard | Extra-fine particle size in Qvar — more peripheral lung deposition at lower doses |
| Budesonide | Pulmicort, Symbicort (with formoterol) | ~BDP equivalent | Preferred in pregnancy; used in nebuliser for children; in combination products |
| Fluticasone propionate | Flixotide, Advair/Seretide (with salmeterol) | ~2× more potent than BDP by dose | Higher adrenal suppression risk at high doses; widely used |
| Fluticasone furoate | Relvar/Breo (with vilanterol); Arnuity | Once daily dosing | Enhanced receptor binding; suitable for once-daily regimen |
| Ciclesonide | Alvesco | Pro-drug; activated in lung | Fewer oral side effects (oral candidiasis); once daily; good for adherence |
| Mometasone | Asmanex, Dulera (with formoterol) | Potent; once or twice daily | Good safety profile; available in combination |
Side effects: Inhaled steroids are much safer than oral steroids. Main local side effects are oral thrush (candidiasis) and hoarse voice — both prevented by rinsing mouth after use and using a spacer. High-dose ICS long-term can cause systemic effects including adrenal suppression, reduced bone density, and skin thinning — which is why the lowest effective dose should always be used.
Combination inhalers contain an ICS plus a Long-Acting Beta-2 Agonist (LABA). LABAs provide sustained bronchodilation (12–24 hours) and enhance the anti-inflammatory effect of ICS. LABAs should never be used without an ICS in asthma — LABA monotherapy is associated with increased asthma-related deaths.
| Combination | Brand(s) | Dosing | Key feature |
|---|---|---|---|
| Budesonide / Formoterol | Symbicort, Fobumix, Duoresp | Twice daily maintenance + as-needed reliever (SMART regimen) | Formoterol is fast-acting → unique dual maintenance/reliever role; reduces exacerbations significantly |
| Fluticasone propionate / Salmeterol | Advair, Seretide, Airduo | Twice daily | Widely used; salmeterol is slow-onset so cannot double as reliever |
| Fluticasone furoate / Vilanterol | Breo Ellipta, Relvar Ellipta | Once daily | Once-daily dosing improves adherence |
| Mometasone / Formoterol | Dulera, Zenhale | Twice daily | Fast-acting formoterol component |
| Beclometasone / Formoterol | Foster, Fostair | Twice daily or SMART | Extra-fine particles; good peripheral deposition; SMART-capable |
The SMART regimen (Single inhaler Maintenance And Reliever Therapy) uses budesonide/formoterol for both regular twice-daily dosing AND as-needed reliever. This approach has the best evidence for reducing severe exacerbations and is now preferred in GINA 2023 guidelines from Step 3 onwards.
The GINA (Global Initiative for Asthma) guidelines use a 5-step stepwise approach. Treatment is stepped up when asthma is uncontrolled and stepped down when well-controlled for ≥3 months.
| Step | Preferred controller | Preferred reliever | Severity |
|---|---|---|---|
| Step 1 | None (or low-dose ICS when symptoms occur) | As-needed low-dose ICS/formoterol or SABA | Infrequent symptoms (<2×/month); no risk factors |
| Step 2 | Low-dose ICS daily | As-needed ICS/formoterol or SABA | Symptoms ≥2×/month but not daily |
| Step 3 | Low-dose ICS/LABA or medium-dose ICS | As-needed ICS/formoterol (SMART) | Daily or frequent symptoms; any risk factor |
| Step 4 | Medium-dose ICS/LABA | As-needed ICS/formoterol (SMART) | Uncontrolled on Step 3; consider add-on LAMA, LTRA, or azithromycin |
| Step 5 | High-dose ICS/LABA + refer to specialist | As-needed ICS/formoterol | Severe uncontrolled asthma → consider biologics; lowest-dose OCS if unavoidable |
Add-on options at Steps 3–5 include: LAMA (tiotropium) for add-on bronchodilation; leukotriene receptor antagonists (montelukast) — particularly for allergic asthma and exercise-induced asthma; theophylline (now less commonly used); and low-dose azithromycin for frequent exacerbators (non-eosinophilic phenotype).
Biologics for severe asthma
Biologic therapies have revolutionised the management of severe asthma over the past decade. These injectable monoclonal antibodies target specific inflammatory pathways driving severe asthma, producing dramatic reductions in exacerbation rates, hospitalisation, and oral corticosteroid use in carefully selected patients.
| Biologic | Target | Brand | Patient selection | Exacerbation reduction |
|---|---|---|---|---|
| Omalizumab | Anti-IgE | Xolair | Allergic asthma; elevated total IgE; sensitised to perennial allergen | ~25–50% |
| Mepolizumab | Anti-IL-5 | Nucala | Severe eosinophilic asthma; blood eos ≥300 cells/μL | ~50% |
| Reslizumab | Anti-IL-5 | Cinqair/Cinqaero | Severe eosinophilic asthma; IV infusion (weight-based dosing) | ~50–60% |
| Benralizumab | Anti-IL-5Rα | Fasenra | Severe eosinophilic asthma; near-complete blood eosinophil depletion | ~50–60%; oral steroid-sparing 75% |
| Dupilumab | Anti-IL-4Rα (blocks IL-4 and IL-13) | Dupixent | Moderate-severe eosinophilic or type-2 asthma; comorbid atopic dermatitis/CRS | ~50–70%; also treats comorbid eczema |
| Tezepelumab | Anti-TSLP (thymic stromal lymphopoietin) | Tezspire | Broadest indication — works across all asthma phenotypes including non-eosinophilic | ~70%; most effective biologic to date |
Biologics are given by subcutaneous injection every 2–8 weeks (most patients self-inject at home after training). Responses are typically assessed at 4–6 months. Candidates are identified through specialist assessment including blood eosinophil count, total IgE, FeNO, and phenotype characterisation. Cost and access remain significant barriers in many countries.
Your asthma action plan
A written personalised asthma action plan is one of the most evidence-based interventions in asthma management — yet fewer than 30% of asthma patients have one. Based on your symptoms and/or peak flow readings, it tells you exactly what to do in three zones:
Asthma in children
Asthma is the most common chronic disease of childhood, affecting 5.1 million children in the U.S. Diagnosis can be challenging in young children — wheezy episodes are common, and many wheezers under age 5 do not go on to develop true asthma.
Key considerations for childhood asthma:
- Diagnosis: Spirometry can be performed reliably from age 5–6. Under 5, diagnosis is based on clinical patterns (recurrent wheeze, family history of atopy, response to bronchodilators) and excluding alternative diagnoses.
- Inhaler technique: Children need spacers and face masks (under 3) or mouthpieces (3 and above) for pMDI inhalers. Dry powder inhalers require sufficient inspiratory flow — generally suitable from age 5+.
- School management: Ensure the school nurse/office has a reliever inhaler; provide a written action plan; children should be able to carry their own inhaler from age 7–8.
- Prognosis: About 50% of children with asthma see significant improvement or apparent remission by adulthood. However, the underlying airway hyperresponsiveness often persists and symptoms can return.
- Allergy: Children with the "atopic march" (eczema → allergic rhinitis → asthma) benefit from early ICS therapy and allergen reduction measures. Early allergen exposure to pets in infancy (before sensitisation) may actually be protective.
Frequently asked questions
Asthma cannot be cured, but symptoms can enter long-term remission — particularly in children whose asthma often improves significantly or appears to disappear by adulthood. However, the underlying airway hyperresponsiveness usually remains, and symptoms can return with new triggers, weight gain, smoking, occupational exposures, or hormonal changes (particularly in women during pregnancy or at menopause). Adults with asthma rarely experience spontaneous remission.
A reliever inhaler (typically a SABA like salbutamol/albuterol — usually blue) is fast-acting, opening the airways within minutes. It is used during symptoms or attacks — but does not treat the underlying inflammation. A preventer inhaler (ICS — usually brown, orange, or purple) is taken daily regardless of symptoms to reduce airway inflammation and prevent attacks. The reliever treats the fire; the preventer stops fires starting. Using a reliever more than twice a week means your asthma is inadequately controlled and you likely need preventer therapy.
Yes — nocturnal worsening is a characteristic feature of asthma. Multiple mechanisms contribute: circadian dips in cortisol and epinephrine (both have bronchodilatory effects), increased airway inflammation during sleep, the supine position promoting gastro-oesophageal reflux which triggers airway inflammation, cooler airway temperatures, and increased overnight allergen exposure from bedding (dust mites). Waking repeatedly with cough, wheeze, or breathlessness is a sign of poorly controlled asthma that should prompt a medication review.
Common triggers include allergens (dust mites, pollen, pet dander, mould), respiratory infections (especially rhinovirus — the common cold), exercise, cold or dry air, air pollutants (cigarette smoke, diesel exhaust, ozone), strong odours and fumes, NSAIDs in NSAID-sensitive asthma, beta-blockers, occupational exposures, gastro-oesophageal reflux, and emotional stress. Triggers are highly individual — keeping a symptom diary to identify your personal triggers is one of the most valuable things you can do for your asthma management.
- Global Initiative for Asthma (GINA). Global Strategy for Asthma Management and Prevention, 2023 Update. Available from: ginasthma.org
- Bateman ED, et al. As-needed budesonide-formoterol versus maintenance budesonide in mild asthma (SYGMA 2). NEJM. 2018;378:1877–1887.
- Rabe KF, et al. Budesonide-formoterol as needed in mild asthma (SYGMA 1). NEJM. 2018;378:1865–1876.
- 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;378:2486–2496.
- Rodrigo GJ, et al. Safety and efficacy of combined long-acting beta-agonists and inhaled corticosteroids vs long-acting beta-agonists monotherapy for stable COPD. Chest. 2009;136(4):1029–1038.
- Asthma and Allergy Foundation of America. Asthma Facts and Figures. 2023.