Extrinsic Allergic Alveolitis

An allergic reaction to inhaled dusts or chemicals, causing cough and fever

  • More common in adults
  • More common in males due to increased risk of occupational exposure
  • Exposure to certain organic dusts and chemicals is a risk factor
  • Genetics is not a significant factor

In some people, inhaling certain dusts or chemicals containing organic substances, such as proteins and fungal spores, triggers an allergic reaction that causes inflammation of lung tissue and shortness of breath. This condition is known as extrinisic allergic alveolitis. The dusts, fungal spores, and chemicals that cause it may be found in the workplace and can affect people in a variety of different occupations.

What are the causes?

Many substances in the workplace can trigger the allergic response that results in extrinsic allergic alveolitis. There are several forms of the disorder, which tend to be named according to the occupation that typically causes them. For example, in farmer’s lung, the allergic reaction is triggered by fungal spores from mouldy hay. If particles from bird droppings are the cause, the disorder is known as bird fanciers’ lung. Other substances that can trigger extrinsic allergic alveolitis include cheese mould, coffee dust, mushroom soil, and certain chemicals that are used in manufacturing products such as insulation and packing materials. Certain microorganisms that may be in air-conditioning systems and humidifiers can trigger the disorder in office environments.

The allergic reaction causes inflammation of the alveoli (air sacs) and small airways in the lungs. The walls of the alveoli thicken, reducing their efficiency in transferring oxygen to the blood, and the airways narrow. Not everyone who is exposed to these dusts and chemicals will develop an allergic reaction if they inhale them. However, some people are particularly susceptible to allergies, and, in such people, exposure to these substances provokes a sudden acute attack. If exposure to the trigger substance continues after the allergy has become established, some people may go on to develop a long-term form of the disorder, which may cause permanent damage to the lungs.

What are the symptoms?

The symptoms of an acute attack of extrinsic allergic alveolitis have a rapid onset and are similar to those of influenza. They usually develop 4–8 hours after initial exposure and may include:

  • Fever and chills.

  • Coughing and wheezing.

  • Tightness in the chest and, in some people, shortness of breath.

If exposure to the substance stops, these symptoms usually begin to clear up spontaneously within 12–24 hours and often disappear completely within 48 hours. If there is further exposure to the substance, sudden attacks are eventually followed by continuous symptoms.

In long-standing (chronic) extrinsic allergic alveolitis, symptoms develop over time and include:

  • Coughing that may become progressively worse over time.

  • Progressive shortness of breath.

  • Loss of appetite and weight loss.

In chronic extrinsic allergic alveolitis, symptoms may continue even after exposure to the substance has stopped. If exposure to the substance continues, progressive lung damage may eventually lead to respiratory failure.

What might be done?

Your work or hobbies may alert your doctor to the diagnosis, which can be confirmed by blood tests to look for antibodies against the substance causing the allergic reaction. Your doctor may also arrange for a chest X-ray and lung function tests to look for evidence of lung damage.

If you have a severe, sudden attack of extrinsic allergic alveolitis, you may be given corticosteroids (see Corticosteroids for respiratory disease) to help to reduce inflammation in the lungs and bronchodilator drugs to help to widen the airways. If the lung damage is severe, you may also be given oxygen (see Home oxygen therapy). In most acute attacks, the symptoms clear up once exposure to the dust has stopped. In long-term cases, continued treatment that includes corticosteroids may be necessary even after exposure to the trigger has ended.

Can it be prevented?

If you become sensitive to substances in your workplace, you should wear a protective mask. Employers should store materials safely and ensure that air conditioners are serviced regularly. You may consider changing your lifestyle or finding alternative employment to prevent the allergy from becoming persistent.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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