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Occupational asthma – causes, treatment and prevention

Written by: Fit for Work team | Posted in: Blog

Chef clapping hands full of flour over fresh doughMore than 5.4 million people in the UK suffer from asthma, a condition that causes a sufferer’s airways to become irritated and constricted, making it harder to breathe. With one in 12 adults suffering with asthma, most of us will know at least someone in our workplace who has the condition.

Asthma is a long-term condition that can start in childhood or occur later in life. It is a condition that is typified by coughing, wheezing, chest tightness and breathlessness that is triggered by a substance that irritates the lining of the airways.

It results from the inflammation of the airways bringing oxygen to and from the lungs. During an attack, the muscles around the airways tighten, the lining thickens and phlegm collects on the walls to restrict the size on the bronchial tubes and make breathing more difficult. The extent of the restriction to the airway determines the severity of the asthma attack.

Asthma and work

Employers should be aware that asthma is a condition caused not just by dust and house mites, or genetic inheritance. Existing asthma can be exacerbated by the working environment. For some people with asthma, exposure to substances in the workplace can aggravate their asthma (work-related asthma). And, for others, certain substances they are exposed to at work can be the cause the asthma (occupational asthma).

Asthma UK estimates that every year 3,000 people will develop occupational asthma after working with known allergenic substances like flour or spray paint. Worryingly, the prognosis for sufferers of occupational asthma is poor, with only 30 per cent of workers fully recovering from their symptoms and an estimated one third of workers with occupational asthma falling unemployed after diagnosis, according to a review by the British Occupational Health Research Foundation.

Experts agree that identifying cases early and offering intervention is the best way to help workers combat and manage occupational asthma.

Types of occupational asthma

Allergic occupational asthma, the most common form, can result from workers being exposed to an allergenic substance (allergen) over a sustained period of time. Eventually the body’s immune system learns to create targeted antibodies to an allergen and responds by making the airways hyper-sensitive to its presence and triggering the tightening and narrowing of the airways that causes breathing difficulties. It usually takes months to years for the body to become sensitised to an allergen but once this has happened even the smallest exposure can trigger an asthma attack.

The most common substances causing allergic occupational asthma in the UK are flour dust and amylase (a bakery enzyme) and isocyanates, which are chemicals found in car paint sprays. This makes the workers in food production, flour mills and bakeries, as well as, those in car paint shops most vulnerable to occupational asthma.

Other industries also experience a high incidence of occupational asthma:

  • Woodworkers, employed in dusty environments.
  • Solderers, affected by the fumes from rosin-based solder flux.
  • Vets and other people working with animals may become sensitive to animal dander or dirty cage bedding.
  • Workers exposed to car exhaust fumes.
  • Health care workers exposed to latex or by products of diathermy (a surgical procedure).
  • Metal workers (exposure to metal working fluids).

Irritant-induced occupational asthma is a non-allergic type of asthma, which can occur when a worker breathes in an irritant substance like a chemical. This is much more uncommon than allergic occupational asthma.  It can happen when there is an accidental chemical spillage of, for example, chlorine (used in swimming pools) or ammonia (used in refrigerators).

Treatment of occupational asthma

The best treatment for occupational asthma is to quickly identify the substance that you suspect is causing your symptoms and then try to avoid contact with it, until you have more information either from your GP or company occupational health team. Diagnosis does not necessarily mean giving up your job, but sometimes the best solution is to move to a different area of the business.

Alternatively, you could try and get allergens removed from your workplace or replaced with safer substances. Extractor fans or improved ventilation could reduce the concentration of the allergen or workers can use respiratory protective equipment (RPE) like face masks, visors, helmets and hoods to reduce the risk of contact with the allergen.

Medication helps to combat the symptoms of asthma. Preventer inhalers used every day cut the risk of asthma attacks by reducing inflammation in the airways and the likelihood of the immune system reacting against the allergen. Having a reliever inhaler also helps sufferers cope with the onset of an asthma attack by quickly relaxing the muscles around the airways and allowing easier breathing within minutes. In allergic occupational asthma, studies have shown that even with medical treatment, if you continue to work whilst breathing in the substances you are allergic to, the drugs become less effective over time and permanent asthma can result.

Advice to employers

Asthma UK has created a charter offering employers five steps to combat occupational asthma within their businesses:

  • Understand the causes of occupational asthma and conditions that trigger symptoms of pre-existing asthma at work and take measures to protect workers.
  • Introduce a programme of health surveillance and access to up-to -date information on preventing occupational asthma.
  • Immediately investigate and diagnose, and provide symptom management and protection for people who develop occupational asthma.
  • Train all employees so that they know what to do if a colleague experiences an asthma attack.
  • Ensure employees understand how to avoid putting themselves and others at risk.

For more detailed information on occupational asthma, see our guidance on the Fit for Work website, or call the free Fit for Work advice line 0800 032 6235, (English) or 0800 032 6233 (Welsh). You can also visit the Advice Hub or go to Those is Scotland can call 0800 019 2211 or visit

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