What is exogenous allergic alveolitis?
Exogenous allergic alveolitis comprises a group of lung diseases. What they have in common is an inflammation of the lung tissue, which usually affects the alveoli and is caused by allergies. The lung disease occurs when a person inhales organic dusts or chemical substances and reacts hypersensitively to them.
On contact with the allergy trigger, the immune system responds with an overshoot and triggers an immune reaction. However, the person affected must have a genetic predisposition, i.e. they must have a certain degree of hypersensitivity. Exogenous allergic alveolitis is also known as hypersensitivity pneumonitis. It is not contagious for other people.
Allergy triggers are often fine particles of bird feathers, wood dust or mold, with which those affected usually come into contact at work and sometimes also in their private lives. Depending on the cause of exogenous allergic alveolitis, experts therefore differentiate between farmer’s lung, bird farmer’s lung, fungal farmer’s lung, humidifier lung (e.g. caused by air conditioning) and other forms. If you contract the disease in your job, it is considered an occupational disease in many countries.
Once the allergen has entered the lungs, sufferers experience symptoms such as shortness of breath, chesty cough, fever and chills. The number one therapy is to avoid the triggering allergen!
Exogenous allergic alveolitis – frequency and age
Exogenous allergic alveolitis rarely occurs in the general population and is therefore a rare disease in adults. Men contract the disease just as often as women. However, EAA is more common in children, usually in the form of bird’s eye lung.
EAA is also more widespread in certain occupational groups. This applies, for example, to farmers, bird breeders and workers who handle chemical substances for a living. In the past, more people contracted this lung disease in their jobs, but thanks to improved occupational health and safety measures, it is now less common. This applies, for example, to farmer’s lung, which now hardly ever occurs due to feeding with silage.
In the case of humidifier lung, however, which is caused by pathogenic germs from air conditioning systems or humidifiers, experts are registering an increasing number of cases – probably because air conditioning systems in cars and buildings are more widespread today than they used to be. Nevertheless, there are no precise figures on the frequency of exogenous allergic alveolitis and the age of those affected.
Exogenous allergic alveolitis: causes and risk factors
Today, experts know of more than 300 different allergens that are possible causes of exogenous allergic alveolitis. There is a wide range of allergy triggers, from chemicals, bacteria and fungal spores to animal and plant proteins (antigens) found in the feathers or droppings of birds.
However, not every person who works in bird breeding or agriculture and inhales organic dusts or chemicals will necessarily contract EAA. Rather, those affected probably have a genetic predisposition to hypersensitivity reactions. Researchers also discuss infections and existing respiratory disease as favorable factors.
Experts distinguish between different forms of exogenous allergic alveolitis depending on the cause:
- Bird lung in animal breeding: The antigens (proteins) are usually found in the feathers or droppings of birds, such as pigeons or budgerigars.
- Farmer’s lung in agriculture: The allergy triggers usually originate from moist hay or straw that contains certain bacteria (heat-loving actinomycetes).
- Humidifier lung: This is usually caused by poorly maintained air conditioning systems, nebulizers or humidifiers; the fine water droplets (aerosols) can contain mould, bacteria or parasites.
- Woodworker’s lung due to wood dust containing mold fungi
- Mushroom grower’s lung due to compost with molds
- Furrier’s lung: animal hair and dust from furs are responsible
- Malt worker’s lung caused by dust from malt and barley, antigens are fungal spores – mostly from molds (Aspergillus)
- Chemical worker’s lung: isocyanates, for example from cooling lubricants
- Machinist’s lung caused by bacteria such as mycobacteria or Pseudomonas
- Indoor alveolitis caused by mold in living spaces
- Detergents due to enzyme proteins from detergents
There are also several other forms of exogenous allergic alveolitis: steam iron alveolitis (bacteria in the water tank), sauna visitor’s lung (fungal spores on moldy wood), wind instrument player’s lung (inhaled bacteria or molds) or pedicure alveolitis (fungi in the skin and toenails).
Symptoms: Exogenous allergic alveolitis is acute or chronic
Exogenous allergic alveolitis can be acute or chronic. In the first case, symptoms set in quickly when you come into contact with large quantities of allergens. Chronic EAA, on the other hand, is gradual and the symptoms gradually set in.
Acute exogenous allergic alveolitis
The symptoms start about four to twelve hours after you have been massively exposed to the allergy trigger, for example when you have moved moldy hay or cleaned the dovecote:
- Shortness of breath at rest without physical exertion
- Irritable cough
- Headaches and aching limbs
- High fever
- Chills
The symptoms disappear after a few days, even without treatment. The acute form can be cured if you completely avoid the allergy trigger. “Allergen avoidance” is the technical term for this.
Chronic exogenous allergic alveolitis
Chronic EAA occurs when you come into contact with small amounts of the respective allergen over a longer period of time. This is the case, for example, if you keep birds in your home. The allergic reactions cause the lung tissue to remodel into connective tissue and the walls of the alveoli to thicken. Pulmonary fibrosis develops. This gradually restricts the gas exchange more and more. Chronic exogenous allergic alveolitis is characterized by uncharacteristic symptoms that can also occur in the context of other diseases. These include, for example:
- Shortness of breath during physical exertion, which gets worse and worse
- Cough (often with sputum)
- Shivering
- Tiredness, fatigue
- Loss of appetite
- Weight loss
- Decrease in physical performance
- General feeling of illness
Diagnosis of exogenous allergic alveolitis
The diagnosis of exogenous allergic alveolitis always begins with a discussion of your medical history, the anamnesis.
Questions we are interested in
- What symptoms do you have and since when? (e.g. cough, shortness of breath?)
- When do they occur during the day?
- How pronounced are your complaints?
- What is your profession?
- Do you come into contact with dusts and chemicals a lot at work (and at home)? If yes: which one?
- Do your symptoms improve, for example, when you are not working or on vacation?
- Do you keep birds at home or do you have contact with these animals in your free time?
- Do you spend a lot of time in air-conditioned rooms? Car, office etc.?
- Do you have any known illnesses, for example infections or a respiratory disease?
- Do you have a family history of respiratory diseases, such as bronchial asthma?
We also usually ask you about your living situation, your everyday activities or hobbies in your free time in order to get to the bottom of the cause of the symptoms. This is usually followed by a physical examination. We listen to the lungs with a stethoscope. A crackling/rattling noise can be detected with an EAA.
We also use the following examinations for diagnosis:
- Lung endoscopy (bronchoscopy): We advance a flexible instrument with a camera and light source into the bronchi, the endoscope. We then flush out the lower airways (bronchoalveolar lavage, BAL). The ratio of certain immune cells in the irrigation fluid (T helper and T suppressor cells) is altered in EAA. In addition, the neutrophil granulocytes (special white blood cells) and later also the lymphocytes are increased.
- Blood test: Antibodies against the allergy trigger (antigens) can be detected in the blood using certain laboratory techniques. The inflammation parameters C-reactive protein and erythrocyte sedimentation rate (ESR) are also elevated in many cases.
- Pulmonary function test: A spirometry, for example, shows whether lung function is impaired.
- X-ray examinationto check the condition of the lungs – in acute EAA, however, X-rays are not very informative.
- Computed tomography (CT): A high-resolution X-ray examination (HR-CT) that provides detailed cross-sectional images of the lungs. Acute EAA and early stages are clearly recognizable on the images.
- Tissue sample (biopsy): This is only necessary if the diagnosis is still unclear.
It is important to distinguish exogenous allergic alveolitis from bronchial asthma and other diseases.
Allergic alveolitis: prevention, early detection, prognosis
There are no special measures for the prevention and early detection of exogenous allergic alveolitis. As a general rule, always visit us promptly if you suffer from shortness of breath, coughing or other complaints. This is especially true if you keep birds at home or work in agriculture. Today, many companies have effective protective measures in place to help employees prevent EAA and other lung diseases. The number of cases has also fallen in recent years.
Course and prognosis of allergic alveolitis
Acute exogenous allergic alveolitis has a good prognosis if you strictly avoid the allergy trigger. Then the course is favorable and EAA is curable. The prognosis for chronic EAA, on the other hand, is less favorable because the changes in the lungs persist even if you avoid the allergy trigger. Pulmonary fibrosis can progress and lead to various complications. These include pulmonary hypertension and right heart failure (cor pulmonale). These worsen the chances of survival. Sometimes only a lung transplant can help.
Exogenous allergic alveolitis: treatment means "allergen avoidance"
The most important treatment for exogenous allergic alveolitis is to avoid the triggering allergen! In future you will have to give “your” allergy trigger a wide berth. This avoidance of allergens usually improves the symptoms. People with avian lung disease not only have to get rid of the animals themselves, but also feather beds and pillows as well as down clothing. If you have humidifier lung, the measures are as follows: Clean and maintain air conditioning systems professionally or remove humidifiers and indoor fountains from living spaces.
EAA: Protective measures at work
It is more difficult if you are exposed to certain allergens in your job. Sometimes it is difficult to avoid the allergy trigger completely. But certain protective measures can reduce the amount of allergens you are exposed to. This includes breathing apparatus for employees or filter systems, for example in agricultural businesses. If it is not possible to completely avoid allergens, you should also consider changing your job. The aim is to prevent serious consequences of EAA such as pulmonary fibrosis.
In some cases, the authorities recognize exogenous allergic alveolitis as an occupational disease. Find out whether this is the case for you.
Exogenous allergic alveolitis – further therapies
The following treatments are also available at EAA:
- Glucocorticoids (cortisone): These drugs are considered to be very effective “anti-inflammatories”. They dampen the immune system and the allergic reaction and alleviate the symptoms. Prednisolone is a frequently used active ingredient. Glucocorticoids are suitable for both acute and chronic EAA.
- Immunosuppressants: We usually use these drugs for chronic EAA. They prevent the disease from progressing and stop existing pulmonary fibrosis. However, immunosuppressants cannot reverse the lung damage. The active substances azathioprine, cyclophosphamide or methotrexate are used, for example
- Pulmonary rehabilitation: There are special pulmonary sports groups that are suitable for patients with respiratory diseases. The sports offer is specially tailored to them.
- Learnbreathing techniques: A physiotherapist will show you special breathing exercises and breathing techniques that make breathing easier and relieve breathlessness.