Farmer’s Lung

What is farmer’s lung?

Farmer’s lung is a type of hypersensitivity pneumonitis, an allergy that causes inflammation in the small air sacs of your lungs (alveoli). You get it from breathing in dust from moldy hay, straw, grain or other crops.

Farmer’s lung causes a different kind of reaction in your body than seasonal or pet allergies. Unlike common allergies that cause hay fever (allergic rhinitis) and asthma, repeated exposure to the moldy dust that causes farmer’s lung can permanently damage your lungs.

Types

Farmer’s lung can be acute, subacute or chronic:

• Acute farmer’s lung causes flu-like symptoms, cough and shortness of breath that come on within a few hours of exposure to the mold. Symptoms go away within hours or days.
• Subacute farmer’s lung usually happens with repeated exposure to low levels of mold. It causes symptoms that linger for a long time or keep coming back.
• Chronic farmer’s lung can happen over time after several acute attacks to higher levels of mold. It causes symptoms that gradually get worse. Chronic inflammation can cause irreversible scarring over time.

What are the symptoms of farmer’s lung?

Acute symptoms of farmer’s lung include:

• Shortness of breath (dyspnea)
• Cough
• Chest tightness
• Chills
• Fatigue
• Fever
• Muscle aches

Subacute and chronic symptoms are similar to acute symptoms, but they can develop slowly and get worse over time. Subacute symptoms might feel like a lingering cold. If you have chronic farmer’s lung, you might notice that you get short of breath more easily than you used to or that you have a cough or fatigue that’s slowly gotten worse. You also lose weight without intending to and have finger or toe clubbing.

What causes farmer’s lung?

Molds that grow on hay, straw and grain cause farmer’s lung. They can release tiny particles — too small to see — into the air when they’re disturbed. When you breathe in the particles, your immune system can overreact and cause inflammation in your lungs. This causes symptoms similar to an allergic reaction.

When you first react to the mold, your body makes chemicals to recognize it in the future. With farmer’s lung and other types of hypersensitivity pneumonitis, as you’re exposed to an allergen again and again, your body becomes more sensitized and responds with worsening reactions. Over time, this damages your alveoli and the small airways that lead to them. The damage causes your symptoms to get gradually worse.

Who’s at higher risk for farmer’s lung?

You’re at a higher risk for farmer’s lung if you work with or are around moldy hay or grain. You might be more likely to have symptoms in late winter or early spring, when hay and grain are more likely to get and stay damp, allowing mold to grow.

You’re at a higher risk for farmer’s lung if you:

• Work on a dairy farm
• Process and load grains
• Handle hay or straw, like breaking open bales that could be moldy
• Spend a lot of time in stables
• Work at a zoo
• Don’t have automated equipment for handling hay or grain
• Are between 50 and 70 years old

What are the complications of farmer’s lung?

With continued exposure to the molds that cause farmer’s lung, you can have serious complications, including:

• Scarring in your lungs (pulmonary fibrosis)
• High blood pressure between your heart and lungs (pulmonary hypertension)

How is farmer’s lung diagnosed?

A healthcare provider diagnoses farmer’s lung based on:

• Your symptoms
• Your health history
• A physical exam
• Blood, imaging and lung function tests
• Whether your work or living environment could expose you to mold

Specific tests used to diagnose farmer’s lung

Your provider might perform or order the following tests:

• Hypersensitivity pneumonitis panel. A provider takes a small sample of blood from your arm using a needle. A lab tests the sample to see if you have signs of a reaction to the proteins that cause farmer’s lung and other types of hypersensitivity pneumonitis.
• Imaging. Chest X-rays and CT scans give your provider images of your lungs so they can look for damage.
• Pulmonary function tests. Most lung function tests involve breathing into a tube attached to a machine to measure how well your lungs are working. Your provider may also check your lung function with blood tests or exercise tests.
• Bronchoscopy. A healthcare provider uses a small, flexible tube passed through your nose or mouth to view the inside of your lungs and collect samples.

How is farmer’s lung treated?

To successfully treat farmer’s lung, you have to stay away from the molds that cause it. Your provider may prescribe medication to reduce inflammation, open your airways or increase your oxygen levels. But even with these medications, farmer’s lung will keep coming back and can cause permanent damage if you continue to be around moldy hay and grain. Chronic farmer’s lung causes damage that may get worse even if you aren’t exposed to the mold anymore.

What medications are used to treat farmer’s lung?

Medications and other treatments used for farmer’s lung include:

• Corticosteroids or immunosuppressive medications. These medications help reduce inflammation. Specific drugs could include prednisone, mycophenolate or azathioprine.
• Anti-fibrotic drugs (pirfenidone and nintedanib). These medications can slow down lung scarring.
• Pulmonary rehabilitation. Exercises and physical therapy can help make it easier to breathe.
• Oxygen therapy. If your condition is severe, you may need extra oxygen. It’s delivered through a mask on your face or tube in your nose.
• Lung transplant. If you have severe lung scarring, you may need a lung transplant.

How soon after treatment will I feel better?

If you have acute farmer’s lung, you might feel better very quickly (within hours or days) just by avoiding the substances that cause the reaction. But it can take several months for your lungs to heal from the inflammation in both acute and chronic farmer’s lung. Some damage might be permanent.

How can I prevent farmer’s lung?

The best way to prevent farmer’s lung is by avoiding exposure to the molds that cause it. If you work around potentially moldy materials, strategies to reduce your risk include:

• Let wet hay, grain and crops dry out before handling them. Store materials in a way that avoids spoilage.
• Use automated machines — rather than people working by hand — whenever possible to handle potentially moldy hay, grain or crops.
• Wear personal protective equipment while around potentially moldy hay, grain or crops. This includes wearing a mask that filters small particles.
• Wet down dusty areas to avoid sending mold into the air when cleaning.
• Make sure buildings with dusty materials are well-ventilated.

What can I expect if I have farmer’s lung?

What you can expect depends on how long you’ve had farmer’s lung and how severe it is. Acute farmer’s lung usually gets better within a few days as long as you’re not exposed to the mold again. Subacute cases can last a few months and are usually treated with medication. You usually can’t cure chronic farmer’s lung, but medication may make your symptoms more manageable.

Can you recover from farmer’s lung?

You can recover from acute and subacute farmer’s lung if you aren’t exposed to the mold anymore. You might need medication to help the inflammation get better.

The damage caused by chronic farmer’s lung is usually irreversible. But you might be able to slow down further damage with treatment and by avoiding additional exposure.

What is the life expectancy for farmer’s lung?

Life expectancy after diagnosis with chronic farmer’s lung depends on whether there’s damage to your lungs and how severe it is. Based on other forms of hypersensitivity pneumonitis, the approximate life expectancy for farmer’s lung is:

• Greater than 15 years after diagnosis for someone with no scarring (fibrosis)
• Around eight years after diagnosis for someone with fibrosis but no other lung damage, like cysts (honeycombing)
• Around three years after diagnosis for someone with severe damage (fibrosis and honeycombing)

A lung transplant can extend your life past these expected timelines.

How do I take care of myself?

If you’ve been diagnosed with farmer’s lung, make a plan with your healthcare provider to reduce the risk of further damage to your lungs. Take all medications as directed by your provider. Ask if there are any physical or breathing exercises you can do at home to improve your lung function.

When should I see my healthcare provider about farmer’s lung?

See a healthcare provider if you have symptoms like cough and shortness of breath that keep coming back or have gotten worse over time. If you have farmer’s lung, see your provider for any new or worsening symptoms.

What questions should I ask my doctor?

It might be helpful to ask your provider:

• How can I avoid exposure to the mold that’s causing farmer’s lung?
• Is there damage to my lungs? How severe is it?
• Is this reversible?
• How do I take my medications?
• How long will it take to feel better?
• When should I follow up with you?