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Asthma Causes

The causes of asthma vary from food allergies to airborne pollen and atmospheric pollution. Asthma can affect anyone at any point in their life but is more prolific in children.

FAQ about Asthma Causes:

What causes asthma?
What causes occupational asthma?
What are the most common allergic triggers of asthma?
Why is asthma on the increase?
How can asthma be prevented?

What causes asthma?

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A typical cause for asthma and asthma attacks is the exposure to a trigger substance, usually by inhalation, which causes an inflammatory response. The body’s immune cells produce a cascade of chemicals, including histamine, which is capable of causing swelling and airway constriction and production of mucus, which causes further airway swelling. Not all asthma is allergic asthma, however. In children, the majority of cases (around 80 per cent) of asthma do have an allergic cause but allergic asthma is less common in adults, apart from occupational (workplace) asthma. These are all asthma causes which will interact with the lungs and cause an inflammatory response, and an asthma attack. Exposure to an allergen gives a specific immune response; involving immune molecules called Immunoglobulin E, and can also give rise to other conditions such as dermatitis or hay fever.

What causes occupational asthma?

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Occupational asthma refers to new cases of asthma in adults, caused by exposure to an allergen they encounter in the workplace setting.

The most common asthmagens are:

  • Welding fumes
  • Isocyanates - used in automotive repair, construction and manufacturing
  • Metal dust
  • Ammonia
  • Tobacco smoke
  • Traffic Pollution
  • Wood dust
  • Cotton Dust
  • Endotoxin - a toxin produced by bacteria that is generated in food processing
  • Enzymes

The Control of Substances Hazardous to Health (COSHH) regulations sets Workplace Exposure Limits for exposure to asthmagens to protect employees.

What are the most common allergic triggers of asthma?

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The most common allergic triggers of asthma are:

Why is asthma on the increase?

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Up to 30 per cent of the UK population is said to suffer from an allergy, including asthma. Hay fever is the most common of the allergic conditions. The prevalence of all allergic conditions has increased over the last 25 years, not just in the UK but in many other countries. In Western Europe, the prevalence of asthma has more than doubled in ten years. This could be because of these key factors:

  • Better awareness and diagnosis of asthma.
  • Modern homes with double glazing, central heating, carpeting and insulation are poorly ventilated compared to homes in the past - which is often compared to living in a plastic bag. This kind of living allows for the accumulation of indoor air pollution, including an increased allergen burden.
  • Changes in the diet which alter the number of bacteria in the gut, making people increasingly prone to developing allergies.
  • A shift from rural to urban living, and an overall increase in the exposure to urban pollution.

How can asthma be prevented?

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While there are several effective medications (preventers and relievers) for managing asthma, prevention of asthma by avoiding exposure to triggers plays a key role in living well with asthma, including allergic asthma.

You can, of course, do more about reducing indoor airborne allergens than outdoor sources of allergens. The most effective way to clean the air in your home is by using an effective air purifier. Here are some further tips:

House dust mite
It is specific proteins within house dust mite droppings that are the allergen, not the mites themselves. Tackle house dust mite by:

  • Regular vacuuming with a cleaner fitted with a High-Efficiency Particulate Air (HEPA) filter or even removing carpets and replacing with hardwood flooring. Carpets are a reservoir for house dust mite.
  • Washing bedding regularly at a high temperature to kill mites; use mite-proof covers for bedding and mattresses.
  • Damp dust regularly (a dry duster spreads dust around, increasing the mite problem). Remove clutter, because this attracts dust.

Pet Dander

  • Ideally, do not have a pet but if getting rid of a beloved family member is a step too far, then ensure the animal is confined, as much as possible, to one room.
  • Shampoo the animal once a week to get rid of dander.


  • Get rid of obvious damp patches.
  • Ventilate bathrooms and kitchens after bathing, showering and cooking to prevent condensation & have a fan operating or open the windows.


  • Try not to bring pollen indoors. Change shoes, clothes and wash hair and shower when coming in from outdoors.


  • Try to avoid exposure to outdoor pollution by keeping your eye on pollution forecasts and planning activities accordingly. Join/support an environmental group like Clean Air in London to put pressure on policymakers for better environmental legislation.

Further information:

Asthma UK Fact sheet -

European Respiratory Society Task Force recommendations on workplace asthma -

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