Causes Of Asthma

What is asthma?

Asthma is a condition that causes airways to swell, become inflamed, narrow and fill with mucus.  In most cases, asthma attacks are caused by environmental triggers such as dust, house mites, pollen, cigarette smoke, and animal fur, although some asthma attacks can be unpredictable. 

Asthma attack

It is possible to suffer from a life-threatening asthma attack. According to the World Health Organisation (WHO)¹ in 2019 asthma caused 461 000 deaths world wide. There is no cure for asthma but it can be managed well if the right medication and dosage are prescribed. Asthma  commonly precipitates in children, but it is possible for adults who have never had asthma to develop it as well. 

Symptoms of asthma

Symptoms typically experienced can include:

  • Breathlessness
  • A whistling sound when breathing called wheezing
  • Chest pain
  • Shoulder pain
  • Back pain
  • Coughing

When the asthma is exacerbated so that it is acute (an asthma attack) other symptoms can include:

  • The chest feel tight
  • Difficult breathing
  • Increase in heart rate and breathing rate
  • Feeling dizzy or drowsy
  • Losing consciousness
  • Blue lips and fingernails

Causes vs triggers

There are specific causes or reasons why asthma occurs in some individuals and not others.  After being diagnosed, patients can learn how to manage the disease in order to prevent it from becoming exacerbated (when symptoms worsen and become more severe). In order to do this it is necessary to know what ‘triggers’ an attack of exacerbated symptoms.

Causes of asthma

There is no singular direct cause or reason why some individuals have asthma but many factors increase risk of developing asthma.

Family history of asthma

There have been many studies to research whether genetics are the cause of asthma and many suggested that the genes you receive from your parents are indeed likely to increase the risk of developing asthma.  A study in the American Journal of Respiratory and Critical Care Medicine (2013)² is a 20 year study that found that individuals who have a first-degree relative with asthma had higher incidence rates of asthma within the first 27 years of life.

Cigarette smoke

Aside from genetics, cigarette smoking can also increase the risk of an individual developing asthma especially if exposed to second-hand smoke during early childhood or during pregnancy. The lungs of the foetus or child are still developing and so are more vulnerable to infection caused by the smoke and toxic chemicals found in tobacco which can cause irreparable damage.

Bronchiolitis in childhood

Bronchiolitis is a chest infection caused by viruses (such as human rhinovirus or respiratory syncytial virus) that infect the airways of infants and cause them to narrow and become inflamed and generally mirrors the symptoms of asthma. Recent research and evidence confirm that this type of infection has a huge influence on the likelihood of an individual developing asthma.

Air pollution

There is a lot of evidence that Industrial fumes from chemicals used by industry or found in traffic fumes can increase the likelihood of an individual developing asthma. Occupational asthma can be caused by inhaling irritants in the workplace. According to the HSE (Health and Safety Executive) in a report called Work Related Asthma Statistics 2021³ there are around an estimated 17,000 new cases of self-reported breathing or lung problems each year.

Common asthma triggers

What ‘triggers’ an asthma attack is often specific to every person.One person may find that exposure to animal fur can cause an exacerbation of their symptoms whilst for another there is little or no reaction.  It is important for each person to identify what specific triggers there are for their condition if they want to keep it under control.  

Physical activity

Even though it's usually considered a positive thing to exercise as it can help to strengthen the lungs and improve general health, unfortunately for some, it can also be a trigger.  This really depends on the individual and asthma can be triggered even by mild exercise whereas for others it may only occur when it is intense, strenuous exercise.

Strong emotions

Strong emotions can also trigger an exacerbation of asthma symptoms. Some individuals find their symptoms are worse when they are stressed, possibly because this can cause heart rate to increase, changing the way we breathe and causing inflammation and constriction of airways.  In a similar way, asthma symptoms may also be exacerbated by laughter.

Cigarette smoke and air pollution

Cigarette smoke and air pollution can both be a cause of asthma and a trigger. They can cause someone who has never had asthma before to develop it but it can also exacerbate the condition for those who already have it.  Any pollutants or irritants inhaled from the atmosphere can cause a negative reaction in the airways.


Asthma is an atopic condition. This means that it is caused by an over-reactive response from the immune system. Allergies are atopic conditions and cause a similar response and so it is understandable that for allergens such as dust, dust, pollen and mould, some food or medication can exacerbate asthma symptoms.


There is no cure for asthma but it can often be well managed with a healthy lifestyle, avoiding triggers and using the correct prescribed medication. To prevent others from developing asthma and to prevent exacerbation of their own symptoms, individuals should refrain from smoking or exposing themselves to pollutants of irritants.


  1. Chronic respiratory diseases: asthma [Internet]. [cited 2022 Nov 23]. Available from: 
  2. Paaso EMS, Jaakkola MS, Lajunen TK, Hugg TT, Jaakkola JJK. The importance of family history in asthma during the first 27 years of life. Am J Respir Crit Care Med [Internet]. 2013 Sep 1 [cited 2022 Nov 23];188(5):624–6. Available from:
  3. HSE, 2021, Work Related Asthma Statistics Great Britain 2021,  Accessed 15 Aug 2022 presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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