Asthma is a chronic inflammatory condition of the airways in which the breathing tubes become sensitive (hyper-responsive) to a wide range of triggers. When exposed to these triggers, the airways can narrow, swell, and produce excess mucus, making it harder to breathe.
This can cause symptoms such as:
- Wheezing
- Coughing
- Chest tightness
- Shortness of breath
- Increased production of sticky mucus (phlegm)
In most people, airway narrowing is reversible, either on its own or with medication, which is why symptoms can be intermittent. However, in some people with long-standing or poorly controlled asthma, ongoing inflammation may lead to persistent or irreversible airflow limitation.
Why symptoms can be worse at night
The body naturally produces hormones (including steroids) that help regulate inflammation. Levels of these hormones fall during sleep, which can allow airway inflammation to increase. As a result, asthma symptoms are often worse at night or in the early morning.
Asthma and sex differences
In early childhood, asthma is more common in boys than girls. By adulthood, this pattern reverses. In the UK, around 60% of adults with asthma are women.
Who is more likely to develop asthma?
The likelihood of developing asthma is higher in people with:
- A history of atopic conditions, such as hay fever or eczema
- A family history of asthma and/or atopic disease
Diagnosis of Asthma
Diagnosing asthma involves a structured clinical assessment. The approach differs slightly between adults and children. An accurate diagnosis is important to ensure the most appropriate treatment and management.
Asthma should be suspected based on a combination of clinical history, symptoms and objective tests of airway inflammation or variable airflow obstruction.
Clinical Assessment
Your healthcare professional will ask about symptoms such as:
- Wheeze
- Shortness of breath
- Chest tightness
- Cough (particularly at night or early morning)
Symptoms that vary over time, are triggered by exercise, allergens, cold air, or respiratory infections, and improve with inhaler treatment may suggest asthma.
A clinical history will also include:
- Personal or family history of asthma, eczema or allergies
- Smoking history
- Occupational exposures
- Previous response to asthma medication
Objective Tests
Current guidelines recommend using objective tests to confirm the diagnosis where possible.
These may include:
- Spirometry to assess lung function
- Bronchodilator reversibility testing to see if lung function improves after inhaled medication
- Fractional exhaled nitric oxide (FeNO) testing to measure airway inflammation
- Peak expiratory flow (PEF) monitoring over several weeks to identify variability in airflow
- Bronchial challenge testing (for example methacholine or exercise testing) in specialist settings if the diagnosis remains uncertain
Additional Investigations
In some cases, further tests may be required to support the diagnosis or rule out other conditions. These may include:
- Allergy testing (for example skin prick tests or blood tests for atopy)
- Blood tests including eosinophil levels
- Chest X-ray if another diagnosis is suspected
Your healthcare professional will review the results of these assessments together to determine whether asthma is the most likely diagnosis and discuss appropriate treatment and follow-up.
Types of Asthma
Allergic (Atopic) Asthma
Triggered by exposure to allergens that irritate the airways, causing asthma symptoms. Common allergens include:
- House dust mites
- Mould and damp
- Pollen (seasonal)
- Pet dander
- Cockroaches
Symptoms may occur shortly after exposure, and management can include allergen avoidance, inhalers, and in some cases, allergy treatment such as immunotherapy.
Non-Allergic Asthma
Triggered by factors other than allergens, including:
- Respiratory infections such as colds or flu
- Air pollution or smoke
- Cold air or rapid changes in temperature
- Chemical fumes or strong odors
Symptoms can occur at any time and are not directly linked to allergen exposure.
Occupational Asthma
Occurs due to exposure to substances at work, for example in:
- Bakeries
- Pottery and ceramics industries
- Construction and building trades
Symptoms may include:
- Wheeze, cough, shortness of breath
- Rhinitis (sneezing, itchy/runny nose)
- Conjunctivitis (itchy, red, inflamed eyes)
Symptoms often improve on days away from work and worsen during or after work. Early recognition is important to prevent long-term lung damage.
Exercise-Induced Asthma (Exercise-Induced Bronchoconstriction)
Symptoms such as coughing, wheezing, chest tightness, or shortness of breath occur during or immediately after physical exertion, and typically improve when activity stops.
Proper warm-up, inhaler use before exercise, and management of underlying asthma help reduce symptoms.
Drug-Induced Asthma
Certain medications can trigger asthma symptoms in susceptible individuals:
- Aspirin and other NSAIDs (e.g., ibuprofen) may induce bronchospasm in aspirin-sensitive asthma
- Beta blockers, including eye drops, are generally avoided in people with asthma
Patients should always inform healthcare providers of their asthma before starting new medications.
