Asthma Explained: Symptoms, Triggers, Causes & Treatment
▶ What is asthma?
Asthma is a chronic inflammatory condition of the airways that causes recurring episodes of wheezing, breathlessness, chest tightness and coughing. It affects around 5.4 million people in the UK. Symptoms are caused by inflammation and narrowing of the airways and are often worse at night or in the morning. Asthma cannot be cured, but with the right treatment — including a preventer inhaler and a reliever inhaler — most people can live normal, active lives with well-controlled symptoms.
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Start Asthma Consultation →What Is Asthma?
Asthma is a common, long-term condition affecting the lungs and airways. People with asthma have airways that are chronically inflamed and particularly sensitive to certain triggers. When exposed to these triggers, the airways can narrow, swell, and produce extra mucus — making breathing difficult.
Asthma affects people of all ages, though it frequently begins in childhood. According to Asthma + Lung UK, around 5.4 million people in the UK are currently receiving treatment for asthma — roughly 1 in 11 children and 1 in 12 adults. It is one of the most common long-term conditions seen in primary care.
Although asthma is not curable, it is highly manageable. Most people with asthma who use their treatments correctly can expect excellent symptom control and a good quality of life.
How Asthma Affects the Airways
In healthy airways, air flows freely through open tubes lined with smooth muscle. In asthma, three things happen simultaneously when a trigger is encountered:
Airway Inflammation
The lining of the airways becomes inflamed and swollen. This is why regular preventer (anti-inflammatory) inhaler use is so important even when symptoms are absent.
Bronchoconstriction
The smooth muscle surrounding the airways contracts and tightens, reducing airway diameter and restricting airflow. This is what the reliever (bronchodilator) inhaler rapidly reverses.
Excess Mucus
The airways produce more mucus than usual, further narrowing the passage and causing the characteristic cough as the body tries to clear the obstruction.
Taken together, these changes produce the hallmark symptoms of asthma: wheezing, breathlessness, chest tightness and cough. The reversibility of these changes with a bronchodilator is a key diagnostic feature of asthma.
Types of Asthma
Asthma is not a single disease. Several subtypes are recognised, each with distinct characteristics:
| Type | Key Features |
|---|---|
| Allergic (atopic) asthma | Most common type. Triggered by allergens such as pollen, dust mites, pet dander, and mould. Often associated with other atopic conditions (hay fever, eczema). Usually onset in childhood. |
| Non-allergic asthma | Triggered by non-allergic factors — cold air, exercise, stress, infections, or irritants such as smoke and strong smells. IgE levels are normal. |
| Occupational asthma | Caused or made worse by substances encountered at work — flour, latex, isocyanates, animal proteins, or chemicals. Improvement at weekends or on holiday is a classic clue. |
| Exercise-induced bronchoconstriction | Airway narrowing triggered by exercise, particularly in cold, dry air. Common in athletes. Usually responds well to pre-exercise reliever inhaler use. |
| Adult-onset asthma | Develops in adulthood, often with no prior history. May be more severe and require higher doses of preventer medication than childhood asthma. |
| Severe/difficult-to-treat asthma | Affects around 4% of people with asthma. Symptoms persist despite high-dose preventer therapy. May require specialist assessment and biologic treatment. |
Symptoms of Asthma
Asthma symptoms can vary from person to person and from episode to episode. The four classic symptoms are:
- Wheezing — a whistling or squeaking sound when breathing, caused by turbulent airflow through narrowed airways
- Breathlessness — difficulty breathing, particularly during or after activity, or when lying down
- Chest tightness — a constricting or squeezing sensation in the chest
- Coughing — often worse at night or in the early morning; may be dry or productive
Symptoms are often worse at night or in the early morning, during exercise, and when exposed to triggers. Some people have mild, infrequent episodes; others experience daily, severe symptoms that significantly limit activity.
Not all wheezing is asthma. Chronic obstructive pulmonary disease (COPD), vocal cord dysfunction, heart failure, and foreign body inhalation can all cause wheezing. Always seek a formal diagnosis before starting treatment.
Common Asthma Triggers
An asthma trigger is anything that irritates the airways and provokes symptoms. Identifying your personal triggers is one of the most effective ways to reduce asthma attacks. Common triggers include:
Allergens
Pollen (grass, tree, weed), house dust mites, cat and dog dander, mould spores, cockroach droppings.
Air Quality
Tobacco smoke, vehicle exhaust, air pollution, strong smells (cleaning products, perfumes, paint fumes).
Weather
Cold or dry air, sudden temperature changes, high humidity, thunderstorms (thunderstorm asthma from fractured pollen grains).
Infections
Common colds, flu, respiratory syncytial virus (RSV), and other respiratory infections are a leading trigger, especially in children.
Exercise
Physical exertion — particularly in cold air. Warming up gradually and using a reliever inhaler before exercise can help prevent exercise-induced symptoms.
Medications
Aspirin, NSAIDs (ibuprofen, naproxen), and beta-blockers can trigger asthma in susceptible individuals. Always inform your doctor of your asthma diagnosis before new medications are prescribed.
How Asthma Is Diagnosed
Asthma diagnosis is primarily clinical — based on your history of symptoms, their pattern, and objective lung function tests. There is no single definitive test. Your GP will typically use a combination of the following:
- 1
Symptom History
Your GP will ask about the pattern of your symptoms — when they occur, what makes them better or worse, whether they wake you at night, and whether you have other atopic conditions (eczema, hay fever). A family history of asthma or atopy is also relevant.
- 2
Spirometry
Measures how much air you can breathe out and how quickly. A reversible obstructive pattern — where FEV1/FVC ratio improves by ≥12% and 200mL after a bronchodilator — supports an asthma diagnosis.
- 3
Peak Expiratory Flow (PEF)
Measured using a hand-held peak flow meter. Serial measurements over 2–4 weeks showing variability of ≥20% support an asthma diagnosis and help assess severity.
- 4
FeNO Test
Fractional exhaled nitric oxide — a breath test measuring airway inflammation. Elevated FeNO (≥40 ppb in adults) supports an allergic/eosinophilic asthma diagnosis and can guide steroid inhaler dosing.
- 5
Bronchial Challenge Test
Used when the above tests are inconclusive. Involves controlled inhalation of methacholine or mannitol to provoke airway narrowing. Performed in specialist settings.
Asthma Severity
Asthma is broadly categorised as intermittent, mild persistent, moderate persistent, or severe persistent based on symptom frequency, night-time waking, and impact on activity. The SIGN/BTS and NICE guidelines use a stepwise treatment approach where treatment is stepped up or down based on symptom control.
Asthma severity can change over time. Good control at one point does not mean treatment can be stopped. Many people step down therapy under medical supervision after 3 months of well-controlled symptoms.
Treatment Overview
Asthma treatment in the UK follows the NICE/SIGN/BTS stepwise guidelines. The main treatment categories are:
- Reliever inhalers (SABA) — short-acting bronchodilators (e.g. salbutamol / Ventolin) for immediate relief of acute symptoms. Used on-demand, not as regular daily treatment.
- Preventer inhalers (ICS) — inhaled corticosteroids (e.g. beclometasone / Clenil, budesonide, fluticasone) reduce airway inflammation. Used daily even when symptom-free.
- Combination inhalers (ICS+LABA) — contain both an inhaled steroid and a long-acting bronchodilator (e.g. Fostair, Seretide, Symbicort). Used when a preventer inhaler alone does not provide adequate control.
- Add-on therapies — montelukast, theophylline, tiotropium, and biologic agents for severe/difficult-to-treat asthma.
For a detailed breakdown of treatment steps, see: Types of Asthma Treatment: From Blue Inhalers to Long-Term Control.
Reliever Inhaler
Ventolin Evohaler 100mcg
Salbutamol pMDI. First-line reliever for acute asthma symptoms and exercise-induced bronchoconstriction.
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Salamol Easi-Breathe 100mcg
Breath-actuated salbutamol inhaler. Easier to use than a standard pMDI — ideal if coordination is difficult.
View & Order →Recognising and Responding to an Asthma Attack
An asthma attack is a sudden worsening of symptoms requiring immediate action. Know the signs:
- Reliever inhaler not relieving symptoms or relief lasting less than 4 hours
- Increasing breathlessness, wheezing, or chest tightness
- Difficulty speaking in full sentences due to breathlessness
- Rapid breathing or increased respiratory rate
- Drowsiness, confusion, or lips/fingernails turning blue (cyanosis)
Call 999 immediately if: your reliever is not working; you cannot speak; your lips are turning blue; you feel confused or drowsy. Never drive yourself to hospital during a severe attack.
While waiting for help: sit upright (not lying down), stay calm, take one puff of your reliever inhaler every 30–60 seconds up to 10 puffs. If no improvement in 15 minutes, call 999 again.
For a comprehensive overview of asthma — causes, symptoms, diagnosis and all treatment options — see our complete asthma condition guide. [Pillar page — link to be activated on publication]
Frequently Asked Questions
What is asthma?
Asthma is a chronic inflammatory condition of the airways that causes recurring episodes of wheezing, breathlessness, chest tightness and coughing. It affects around 5.4 million people in the UK. The airways become inflamed and narrowed in response to triggers, making breathing difficult. It cannot be cured but can be very well controlled with appropriate treatment.
Is asthma curable?
There is currently no cure for asthma. However, with the right treatment — a daily preventer inhaler and an on-demand reliever inhaler — most people with asthma experience excellent symptom control and live normal, active lives. Some children with mild asthma appear to “grow out of it” but symptoms may return in adulthood.
What triggers an asthma attack?
Common triggers include pollen, pet dander, dust mites, mould spores, cold air, cigarette smoke, air pollution, exercise, respiratory infections, stress, and medications such as aspirin and NSAIDs. Triggers vary between individuals — keeping a symptom diary can help identify yours.
Can adults develop asthma for the first time?
Yes. Adult-onset asthma is common and can develop at any age. It is often triggered by occupational exposures, hormonal changes, respiratory infections, or new allergies. Diagnosis in adults can be delayed as symptoms are sometimes attributed to COPD, heart disease, or deconditioning.
When should I call 999 for asthma?
Call 999 immediately if your reliever inhaler is not helping, you cannot finish sentences, your lips or fingernails are turning blue, you feel confused or drowsy, or symptoms are rapidly worsening despite treatment. These indicate a potentially life-threatening asthma attack requiring emergency care.
References
- NICE (2024). Asthma: diagnosis, monitoring and chronic asthma management. NG245. nice.org.uk/guidance/ng245
- SIGN/BTS (2023). British Guideline on the Management of Asthma. SIGN 158.
- Asthma + Lung UK (2024). Asthma Facts and Statistics. asthma.org.uk
- NHS (2023). Asthma — Overview. nhs.uk/conditions/asthma
- Global Initiative for Asthma (GINA) (2024). Global Strategy for Asthma Management and Prevention.