Hypersensitivity pneumonitis is a lung disease that causes the lungs to become inflamed as a result of an allergic reaction. Often, symptoms do not develop immediately, but rather they develop with continued exposure. Symptoms may also develop after a highly concentrated exposure.
The allergic reaction that causes hypersensitivity pneumonitis is caused by certain allergens, such as:
When these allergens are breathed in, the small air sacs in the lungs can become inflamed. These tiny air sacs are filled with white blood cells, and inflammation can cause fluid to build up. As a result of continued exposure to allergens, scar tissue may begin to form in the air sacs, which can impact respiratory function.
Various types of allergens can cause hypersensitivity pneumonitis. While the best method of prevention is avoiding these substances, people who work in construction, mining, maritime, or foundry occupations may not be able to completely avoid exposure.
How Common is Hypersensitivity Pneumonitis?
Researchers have identified more than 300 triggers for hypersensitivity pneumonitis. Even with so many triggers, the prevalence of the disease remains relatively low. Between 2004 and 2013, it was estimated that between 1.67 to 2.71 people per 100,000 had the disease. That prevalence rate equaled to 7,498 people with a diagnosis.
There are a few reasons why hypersensitivity pneumonitis rates are relatively low compared to rates of other occupational diseases, such as silicosis. These reasons include:
- Immune System Response – Everyone’s immune system responds differently. Therefore, two people who work in the same environment and are exposed to the same allergen may have completely different immune system responses. One person may develop an allergic reaction, and another may not.
- Reversibility – In the early stages, the disease is completely reversible with proper treatment and avoidance of triggers.
Because hypersensitivity pneumonitis can be treated, or even reversed, it is more difficult to identify a number of people who suffer from the disease.
Types of Hypersensitivity Pneumonitis
There are three different types of hypersensitivity pneumonitis, each with individual symptoms, treatment methods and prognosis. These types include:
- Acute – Acute hypersensitivity pneumonitis occurs in people who have high levels of exposure to triggers. The symptoms are similar to asthma, including:
- Chest tightness
- Respiratory crackles
- Chronic – Chronic hypersensitivity pneumonitis occurs in people with low levels of exposure, who have been exposed over longer periods of time. Exposure is often over a period of months or years. Symptoms generally progress over time, and include:
- Productive cough
- Weight loss
- Respiratory failure (advanced cases)
- Heart failure (advanced cases)
- Subacute – Subacute hypersensitivity pneumonitis falls between the other two levels, and develops over a period of days or weeks. Symptoms may include:
Many of these symptoms also occur in other lung diseases or disorders. Proper diagnosis is the key to managing symptoms.
To identify hypersensitivity pneumonitis, doctors will conduct a thorough examination, review medical and lifestyle history, and discuss symptoms. Furthermore, doctors will look for clues in the medical and lifestyle history that may indicate you have the disease. These clues may include:
- Recurring pneumonia
- Symptoms that onset after moving to a new home
- Symptoms that onset after changing occupations
- History of standing water, swimming pool, hot tub, or water damage in the home
- Birds kept as pets
- Symptoms that improve or worsen in other environments
In addition to gathering a detailed history, a series of diagnostic tests are common. These tests include:
- Chest x-rays
- High-resolution computed tomography (HRCT)
- Pulmonary function tests
- Lung biopsy
Depending on symptoms and overall health, other tests may also be necessary.
In the early stages of hypersensitivity pneumonitis there is minimal lung damage and the inflammation can be treated or reversed. With long-term exposure, however, lung scarring becomes more likely. This scarring is permanent, and therefore, there is no cure.
Symptoms of hypersensitivity pneumonitis are manageable, however. For people with mild allergic reactions steroids are a common treatment method with a duration ranging from 10 days to three months. More severe cases may require a longer duration of steroids. Furthermore, additional treatment interventions may be possible depending on the symptoms and type.
What Workers Should Know
If you work in an occupation that exposes you to dust, mold or other allergens, the most important thing is taking measures to prevent inhaling harmful particles. Consequently, workers should use personal protective equipment (PPE), such as respirators, to prevent breathing in harmful substances.
Employers must provide PPE if harmful substances or toxins are present in the work environment. Employers are also required to manage the work environment, assess for hazards and ensure that workers get medical care if needed.