This page looks at a group of allergic lung diseases which are linked to exposure to dust, called extrinsic allergic alveolitis (EAA). A common and well known type is called ‘farmer’s lung’.
What is extrinsic allergic alveolitis
What causes extrinsic allergic alveolitis?
What are the symptoms?
How is extrinsic allergic alveolitis diagnosed?
How is extrinsic allergic alveolitis treated?
Who is at risk?
Dust control to prevent extrinsic allergic alveolitis
Further advice
What is extrinsic allergic alveolitis
EAA refers to a group of lung diseases that you can develop after exposure to certain animal and vegetable dusts. ‘Extrinsic allergic alveolitis’ describes the origin and the nature of these diseases:
- ‘extrinsic’ – caused by something that is outside of the body
- ‘allergic’ – a highly sensitive reaction of the body to a specific substance
- ‘alveolitis’ - inflammation in the small air sacs of the lungs (alveoli).
What causes extrinsic allergic alveolitis?
EAA is caused by exposure to a very large variety of substances including certain animal or vegetable dusts over varying lengths of time – anything from weeks to years.
These dusts are a complicated mixture of substances often containing allergy-causing micro-organisms (tiny living particles). These dusts can be from:
- husks
- bark
- wood
- mouldy hay, straw and sugar cane
- straw
- grain
- insects and insect fragments
- birds
- dried urine of rodents
- animal dander (old skin scales that are constantly shed)
- mushroom compost
- metal working fluids
- certain drugs
- bacteria
- fungi.
Micro-organisms also produce toxic chemicals that form part of the dust.
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What are the symptoms?
Once you have become sensitive to these dusts, there are three different types of response:
- acute (intense and sudden)
- sub-acute (gradual on-set of symptoms)
- chronic (long term).
Depending on how long you were exposed to dust and how at risk your lungs are, your symptoms may include:
- a cough
- shortness of breath
- sweating
- sore throat
- headache
- nausea.
If these symptoms continue and the condition develops then you may suffer:
increasing breathlessness
- occasional fever
- loss of weight
- lack of energy.
Your lungs may become permanently damaged and, in the extreme cases, EAA can be fatal.
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How is extrinsic allergic alveolitis diagnosed?
The best evidence for the cause of EAA is obtained by looking at your job history or personal history. The doctor can then work out which animal or vegetable dusts you might have come into contact with.
If your GP believes you have EAA you will be referred to a specialist for medical tests. The tests will look for alveolitis (inflammation of the air sacs). First the specialist will listen to your chest for crackling sounds as you breathe in. The specialist may then need to do lung function tests, and send you for an x-ray and CT scan. You may also have a test called a fibreoptic bronchoscopy. This is where a thin tube with a camera on the end is guided into your airway (your throat will be numbed first with local anaesthetic and you may be offered a sedative as well to relax you). This test is done to examine the lungs and obtain samples. You may also need blood tests to determine what it is you are allergic too.
How is extrinsic allergic alveolitis treated?
Following diagnosis, the safest approach is to avoid coming into contact with the animal or vegetable dusts that caused your EAA. This should improve your health and prevent the illness getting worse. For serious cases, you may need medications that make breathing easier.
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Who is at risk?
You can get EAA in many different environments and in many different jobs. The following table lists some of the diseases, and shows how you can get the disease.
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Examples of extrinsic allergic alveolitis
|
|
| Disease |
Exposure |
| Air conditioner lung |
Tiny particles contaminating the water in humidifier systems |
| Animal handler’slung |
Dander, hair particles, dried rodent’s urine |
| Bagassosis |
Tiny particles contaminating sugar cane after the sugar has been extracted (baggasse) |
| Cheese washer’s lung |
Cheese mould |
| Farmer’s lung |
Mouldy hay, straw, grain |
| Malt-worker’s lung |
Mouldy malt |
| Mushroom worker’s and mushroom farmer’s lung |
Mouldy mushroom compost |
| Sewage sludge disease |
Dust of heat-treated sludge |
| Wheat weevil lung |
Weevil contamination of grain and flour |
| Suberosis |
Mouldy cork dust |
| Wood pulp worker’s disease |
Mouldy wood chips |
|
|
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Dust control to prevent extrinsic allergic alveolitis
There are three basic steps you can take to reduce the amount of dust you come into contact with:
- Ventilation - local exhaust ventilation and general ventilation both help
- Separate yourself from any dusty processes and use personal protective equipment
- Education - it is important to know that certain dusts can cause diseases. Managers and workers should learn about ways to store materials so that they minimise mould formation and reduce dust. The Control of Substances Hazardous to Health (COSHH)Regulations require employers to control exposures to hazardous substances to protect employees’ health.
On farms, you can reduce the possibility of EAA by:
- Using well-designed, leak proof ducting and enclosed conveyor systems for grains and feeds
- Using local ventilation systems in any egg handling areas or feed storage and/or preparation areas
- Making sure ventilation is effective and provides plenty of fresh, replacement air
- Fitting the enclosed cabs of tractors and combine harvesters with air filters
- Storing vegetables in a way that means there is little possibility of it being contaminated by micro-organisms. Making sure that vegetables are dry before storage and stored in a dry environment.
- Personal protective equipment is very important, but it should be considered as the last resort for respiratory protection. It is not a substitute for proper dust control.
Respirators, including dust masks, are best used when:
- engineering or administrative controls are not technically possible
- engineering controls are being installed or repaired
- there is an emergency or other temporary situation – for example, maintenance operations.
If you need respiratory protective equipment for a job, then a full respiratory programme should be put in place that includes selection, use, and care of respirators. You should also receive a training and education programme.
Remember, there is a range of respirators that give different levels of protection. It is important to identify what the dust is so you can choose the right respirator.
Further advice
You can ask your doctor or get in touch with the UK Health and Safety Executive - helpline: 0845 345 0055 w: www.hse.cov.uk
You can also call the British Lung Foundation Helpline on 08458 50 50 20 – open from 10am to 6pm Monday to Friday.
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Last medically reviewed: November 2008
