This page looks at a group of lung diseases linked to allergic exposure to dust called extrinsic allergic alveolitis (EAA). The most common type is called ‘farmer’s lung’.
What is extrinsic allergic alveoltis?
What causes extrinsic allergic alveoltis?
What are the symptoms?
How is extrinsic allergic alveoltis diagnosed?
How is extrinsic allergic alveoltis treated?
Who is at risk?
How can extrinsic allergic alveoltis be prevented?
Further advice
What is extrinsic allergic alveoltis?
EAA refers to a group of lung diseases that you can develop after exposure to animal and vegetable dusts. ‘Extrinsic allergic alveolitis’ describes the origin and the nature of these diseases:
- ‘extrinsic’ – caused by something outside the body
- ‘allergic’ – caused by a reaction of the body to a specific substance or condition
- ‘alveolitis’ - an inflammation in the small air sacs of the lungs (alveoli)
EAA is caused by:
- exposure to animal or vegetable dust over a prolonged period
- heavy exposure to animal or vegetable dust over a short period.
Animal and vegetable dusts are a complicated mixture of substances. They can include:
- husks
- bark
- wood
- mouldy hay
- straw
- grain
- insects and insect fragments
- bird droppings
- dried urine of rats
- animal dander (old skin scales that are constantly shed).
The dusts are also made up of micro-organisms including bacteria and fungi. Micro-organisms also produce toxic chemicals that form part of the dust.
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What are the symptoms?
Once a person is sensitised to EAA, there are three different types of response:
- acute (intense)
- sub-acute (recurrent)
- chronic (long-term).
If you are exposed to relatively low levels of dust, symptoms are:
- a cough
- shortness of breath
- sweating
- sore throat
- headache
- nausea.
If the attacks and symptoms continue, then you will get chronic symptoms:
- increasing shortness of breath
- occasional fever
- loss of weight
- general lack of energy.
Your lungs will be permanently damaged and, in the worst cases, EAA can be fatal.
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The best evidence for EAA comes from your job history and the animal or vegetable dusts you have been in contact with.
Although your doctor may want to do some tests, such as lung x-rays, blood tests or lung function tests, they are not specific and may not distinguish EAA from other lung problems.
Following diagnosis, you must avoid coming into contact with animal and vegetable dusts. This alone will improve your health. For serious cases, you may need medications that make breathing easier.
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You can get EAA in many different jobs. The following table lists some of the diseases, how you get them and how you can prevent them.
| Examples of extrinsic allergic alveolitis |
| Disease | Exposure | Prevention |
| Air conditioner lung | Humidifier water | Maintenance of air and water handling systems |
| Animal handler’s lung | Dander, hair particles, dried rat’s urine | Good exhaust ventilation |
| Bagassosis | Mouldy sugar cane | Application of 1% propionic acid to bagasse. Good exhaust ventilation. Enclosure of processes |
| Bird fancier’s lung | Droppings and feathers | Good exhaust ventilation. Spray droppings with water when cleaning |
| Cheese washer’s lung | Cheese mould | Wrap the cheese in foil during ageing |
| Farmers' lung | Mouldy hay, straw, grain | See ‘Dust Control’ in next section |
| Malt-worker's lung | Mouldy malt | Application of mechanical methods in the malting process |
| Maple bark strippers' disease | Mouldy maple bark | Spray logs during debarking. Remote control of some operation |
| Mushroom workers' lung | Mouldy mushroom compost | Good exhaust ventilation |
| Sequoiosis | Mouldy sawdust | Good exhaust ventilation. Enclosure of processes |
| Sewage sludge disease | Dust of heat-treated sludge | Good exhaust ventilation. At outside facilities, you should stand upwind of storage piles |
| Wheat weevil lung | Mouldy grain, flour, dust | See "Dust Control" in next section. |
| Suberosis | Mouldy cork dust | Good exhaust ventilation |
| Wood pulp workers' disease | Mouldy wood chips | Good exhaust ventilation. Remote control of some operations. |
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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 animal and vegetable dusts can cause diseases. Managers and workers should learn about ways to store materials so that they stop mould formation and reduce dust.
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 monitoring the temperature and relative humidity in enclosed livestock units
- effective ventilation and plenty of fresh, replacement air is also important
- fitting the enclosed cabs of tractors and combine harvesters with air filters
- personal protective equipment is very important, but it should be considered as the last resort for respiratory protection. Personal protective equipment is not a substitute for proper dust control.
Respirators, including dust masks, should only be 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 are 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.
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You can ask your doctor or get in touch with the UK Health and Safety Executive - helpline: 0845 345 0055 w: www.hse.gov.uk.
You can also call the British Lung Foundation helpline on 08458 50 50 20 – open from 10am to 6pm Monday to Friday.
Page last medically reviewed: Aug '05
