What is Asthma?
The word asthma is from the Greek ἆσθμα (âsthma), which means 'panting'.[1]
What is Asthma?
Asthma is a chronic (long-term) condition that affects the airways in the lungs. The airways are tubes that carry air in and out of your lungs. If you have asthma, your airways can become inflamed and narrowed at times. This makes it harder for air to flow out of your airways when you breathe out. Asthma often begins in childhood, and can be triggered by cold air, viral infections, inflammatory foods, stress, allergens such as dust mites, smoke, animal dander, or pollen.(2).
What causes Asthma?
Asthma is caused by swelling (inflammation) of the breathing tubes that carry air in and out of the lungs. This makes the tubes highly sensitive, so they temporarily narrow.
What are the Symptoms?
When someone has an asthmatic episode, symptoms include wheezing, breathlessness, chest tightness, coughing, irritability, feelings of air hunger, feelings of constriction in the chest and airways, difficulty getting a breath, excess mucus, noisy breathing, faster breathing rhythm, upper chest breathing, and mouth breathing. Episodes can be more or less severe, there can be extended periods of low level symptoms, punctuated by more severe episodes.
How Prevalent is Asthma?
The American National Institute of Health statistics show asthma affects 1 in 13 people of all ages (2). The UK National Health Service statistics show that 1 in 11 children have asthma with 1 million children receiving treatment. (3).
How does it impact people's daily lives?
The effects can be more or less severe. Chronic low-level symptoms are typically managed by medication, which means that you can continue life relatively normally, engaging in school, work, and sports. However, you may notice that you have less resiliency, and the symptoms contribute to feelings of fatigue, breathlessness, air hunger, excess mucus, difficulty engaging in exercise, feelings of stress, and irritability. These symptoms are typically managed through asthma medication.
More severe symptoms have a significant impact on daily life. You may need to take time off work and school or avoid sports. During a more severe asthmatic episode, you may need to go to a hospital for medical intervention to help you breathe. In these times, breathing will be significantly stressed, with heavy, noisy wheezing, blocked airways, irritability, and overwhelming feelings of stress and panic.
How serious is the condition?
Asthma is a serious medical condition. Even mild symptoms have a significant impact on quality of life. A severe episode can be life-threatening; every 10 seconds, someone in the UK has a life-threatening attack, with attacks killing three people in the UK every day (4).
Types of Asthma (6)
Asthma is classified based on its causes and severity. Healthcare providers categorize asthma as either intermittent or persistent, and further classify it based on whether it is atopic (allergic) or non-atopic (non-allergic).
Asthma by Severity
- Intermittent Asthma: Symptoms come and go, with normal breathing between episodes.
- Persistent Asthma: Symptoms occur frequently and can be classified as mild, moderate, or severe, depending on how often they happen and how much they affect daily activities.
Asthma by Cause
- Atopic (Allergic) Asthma: Triggered by allergens such as mold, pollen, dust mites, and pet dander. This type of asthma is linked to allergic conditions like hay fever and eczema.
- Non-Atopic (Non-Allergic) Asthma: Triggered by factors unrelated to allergies, such as stress, infections, exercise, cold air, smoke, or strong odors.
Asthma by Age of Onset
- Pediatric Asthma (Childhood-Onset): Typically starts before the age of 5 and can occur in infants and toddlers. Some children may outgrow asthma, but it’s important to consult a healthcare provider to determine if an inhaler is needed.
- Adult-Onset Asthma: Begins after age 18. This type is often non-atopic and may be linked to respiratory infections, stress, or environmental factors.
Other Specific Types of Asthma
- Exercise-Induced Asthma (Exercise-Induced Bronchospasm): Symptoms occur during or after physical activity, often due to rapid breathing in dry or cold air.
- Occupational Asthma: Develops due to repeated exposure to workplace irritants like dust, chemicals, fumes, or allergens.
- Asthma-COPD Overlap Syndrome (ACOS): A condition where a person has both asthma and chronic obstructive pulmonary disease (COPD), leading to persistent breathing difficulties.
Diagnosing and Asthma Tests
resource (7)
To check how well your lungs are working, your GP or nurse may perform one or more breathing tests. These tests involve blowing into special devices and can usually be done during your appointment. Some tests may need to be repeated later to confirm an asthma diagnosis.
Common Asthma Tests:
- Peak Flow Test – Measures how quickly you can blow air out of your lungs.
- Spirometry – Measures how much air you can forcefully exhale in one breath.
- FeNO Test (Fractional Exhaled Nitric Oxide) – Measures nitric oxide levels in your breath, which can indicate airway inflammation.
In some cases, your GP or nurse may give you a peak flow meter to use at home. You'll take readings over two or more weeks and record your results in a peak flow diary. At your follow-up appointment, your GP or nurse will review your readings to see if your pattern suggests asthma.
Asthma Medications
LongTerm Control & Quick Relief
Source (8)
Managing asthma often requires a combination of long-term control medications to prevent symptoms and quick-relief medications to treat sudden flare-ups.
Long-Term Control Medications
(Taken daily to prevent symptoms and reduce inflammation.)
1. Inhaled Corticosteroids (ICS) – First-line treatment for most people
These anti-inflammatory drugs reduce airway swelling and tightening. Regular use helps prevent asthma attacks.
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Common ICS medications: Fluticasone (Flovent), Budesonide (Pulmicort), Mometasone (Asmanex), Beclomethasone (Qvar), Ciclesonide (Alvesco)
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Side effects: Minor, but may include throat irritation or oral yeast infections (reduced by using a spacer and rinsing the mouth after use).
2. Leukotriene Modifiers – Controls asthma for up to 24 hours
These block leukotrienes, chemicals that cause airway inflammation.
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Examples: Montelukast (Singulair), Zafirlukast (Accolate), Zileuton (Zyflo)
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Note: Montelukast has been linked to rare psychological side effects like agitation, depression, or suicidal thoughts.
3. Long-Acting Beta Agonists (LABAs) – Opens airways for 12+ hours
These bronchodilators relieve airway constriction and are taken on a schedule to control moderate to severe asthma. However, they must be used with an inhaled corticosteroid to prevent severe asthma attacks.
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Examples: Salmeterol (Serevent), Formoterol
4. Long-Acting Muscarinic Antagonists (LAMAs) – Alternative bronchodilators
Used if LABAs cannot be taken or to enhance treatment.
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Example: Tiotropium (Spiriva Respimat)
5. Combination Inhalers – ICS + LABA for better control
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Examples: Advair (Fluticasone/Salmeterol), Symbicort (Budesonide/Formoterol), Dulera (Mometasone/Formoterol), Breo Ellipta (Fluticasone/Vilanterol)
Quick-Relief Medications
(Used as needed for sudden symptoms.)
1. Short-Acting Beta Agonists (SABAs) – Immediate relief within minutes
These relax airway muscles and work for 4-6 hours.
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Examples: Albuterol (ProAir, Ventolin), Levalbuterol (Xopenex)
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Often used before exercise to prevent symptoms.
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Side effects: Jitteriness, rapid heartbeat.
2. Ipratropium (Atrovent) – Short-acting bronchodilator
Used alone or with SABAs for asthma attacks, though primarily prescribed for COPD.
3. Theophylline – Older bronchodilator taken as a pill
Helps with nighttime asthma symptoms but requires regular blood tests to monitor dosage.
4. Oral Corticosteroids – For severe asthma attacks
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Examples: Prednisone, Methylprednisolone
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Only used short-term due to serious long-term side effects (bone thinning, high blood pressure, muscle weakness, etc.).
Medications for Asthma Triggered by Allergies
1. Allergy Shots (Immunotherapy)
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Used when avoiding allergens isn’t enough.
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Requires regular injections over 3-5 years to gradually reduce sensitivity.
2. Sublingual Immunotherapy Tablets
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Alternative to shots, dissolving under the tongue.
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Effective for grass, ragweed, and dust mite allergies.
3. Allergy Medications (Not substitutes for asthma treatment, but help manage symptoms.)
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Antihistamines, decongestants, nasal corticosteroid sprays (e.g., cromolyn)
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Nasal decongestants should not be used for more than 2-3 days to avoid rebound congestion.
History of Asthma
Source: (5)
The word asthma comes from a Greek word meaning "shortness of breath" and was originally used for anyone who struggled to breathe. In the 19th century, Dr. Henry Hyde Salter refined the definition, describing asthma as episodes of breathing difficulty followed by normal breathing. He observed that the airways tighten due to muscle contractions and that black coffee could help ease symptoms—something he discovered through his own experience with asthma.
Sir William Osler, a key figure in modern medicine, further expanded on asthma’s causes. In 1892, he described it as a condition involving muscle spasms in the airways, swelling, and inflammation. He noted that asthma often ran in families and could affect people from childhood to old age. He also identified common triggers like dust, pollen, pet dander, strong emotions, certain foods, and respiratory infections. His approach helped doctors see asthma as a distinct medical condition with specific causes and treatments.
Asthma Treatment
Early asthma treatments focused on relaxing the airway muscles using natural compounds like theophylline (found in coffee), ephedrine, and adrenaline. By the mid-20th century, new medications like salbutamol and terbutaline became widely used.
These drugs were so effective that they were sometimes overused, leading to spikes in asthma-related deaths in the 1960s and 1980s. This highlighted the need to better understand asthma beyond just muscle spasms.
In 1921, scientists discovered IgE, an antibody linked to allergic reactions. This explained why many people with asthma react to dust mites, pollen, and animal dander.
Asthma as an Inflammatory Disease
By the 1980s, researchers learned that asthma attacks happen in two stages:
- Early reaction – The immune system releases chemicals that trigger symptoms.
- Late reaction – Other immune cells cause ongoing airway sensitivity.
This led to treatments like mast cell stabilizers (e.g., sodium cromoglicate) and inhaled steroids (e.g., beclomethasone), which reduce inflammation and prevent attacks. Scientists also found that mast cells release substances like histamine, which worsen symptoms. However, the exact process behind these immune responses was still unclear.
How Asthma Changes the Airways
Over time, asthma can cause lasting changes in the airways, especially in severe cases. These changes, called airway remodeling, include:
- More mucus production
- Thickened airway walls
- Extra smooth muscle and blood vessel growth
Scientists believe this happens because the airway lining struggles to repair itself properly. People with asthma often have a weaker airway barrier, making them more sensitive to allergens, pollution, and viruses.
Respiratory infections, especially the common cold, are major asthma triggers. In cooler climates, asthma attacks tend to spike in autumn due to colds and in spring due to pollen. In warmer regions, these seasonal trends are less noticeable.
How Infections Trigger Asthma Attacks
People with asthma are more prone to respiratory viruses, especially colds, because their airways produce fewer virus-fighting proteins. This allows infections to spread more easily, worsening symptoms. Scientists are now testing inhaled interferon-beta as a possible treatment for virus-induced asthma attacks.
Research also shows that early childhood infections increase asthma risk more than allergens. Children who are genetically prone to asthma may develop the condition after repeated exposure to colds, pollution, and smoke, which overstimulates their immune system.
Asthma, Airway Changes, and the ADAM33 Gene
In 2000, researchers found that asthma may reactivate a process normally used to develop lungs in a fetus. This leads to excessive airway muscle growth, new blood vessel formation, and thicker airway walls—making asthma worse.
A key gene in this process is ADAM33, the first gene linked to asthma. It affects airway remodeling and is connected to childhood asthma, poor lung function, and severe cases. Scientists later found that ADAM33 exists in two forms:
- Membrane-bound ADAM33 – Stays attached to cells.
- Soluble ADAM33 (sADAM33) – Found in higher amounts in people with severe asthma.
Recent research suggests sADAM33 may also promote airway muscle and blood vessel growth, making it a key factor in asthma’s progression.
Sources
- Murray JF (2010). "Ch. 38 Asthma". In Mason RJ, Murray JF, Broaddus VC, Nadel JA, Martin TR, King Jr TE, Schraufnagel DE (eds.). Murray and Nadel's textbook of respiratory medicine (5th ed.). Elsevier. ISBN 978-1-4160-4710-0.
- https://www.nhlbi.nih.gov/health/asthma
- https://www.england.nhs.uk/childhood-asthma/
- https://www.nhs.uk/conditions/asthma/asthma-attack/
- Holgate ST. A brief history of asthma and its mechanisms to modern concepts of disease pathogenesis. Allergy Asthma Immunol Res. 2010 Jul;2(3):165-71. doi: 10.4168/aair.2010.2.3.165. Epub 2010 May 6. PMID: 20592914; PMCID: PMC2892047.
- https://my.clevelandclinic.org/health/diseases/6424-asthma
- https://www.asthmaandlung.org.uk/conditions/asthma/diagnosing-asthma
- https://www.mayoclinic.org/diseases-conditions/asthma/in-depth/asthma-medications/art-20045557