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Farmer’s Lung Disease

Farmer's lung is a lung condition linked to breathing moldy dusts, most often from hay, straw or grain. Understanding the warning signs can help you seek care early.

What is farmer's lung?

Farmer's lung is a form of hypersensitivity pneumonitis, an immune reaction in the lungs to certain dusts. It is most often associated with spores from molds and bacteria that grow in damp hay, straw, silage or grain. It is not an infection that spreads from person to person.

Medical sources such as the CDC and NIOSH describe it as an occupational lung disease in agriculture. Only a clinician can diagnose it, so this guide explains the concept and points you to proper care.

The name is old, but the condition is real and still recognized today. Because it is rare for the average person but significant for those who develop it, awareness among farm families is worthwhile.

What are the symptoms?

Symptoms can look like the flu at first. After heavy exposure, some people develop cough, shortness of breath, chest tightness, fever, chills and tiredness within hours. These may ease after a day or two away from the exposure and then return the next time.

With repeated exposure, some people develop a more persistent cough and breathlessness, and lung damage can occur in some cases. That is why recurring flu-like episodes after barn work should not be brushed aside.

Many people mistake early episodes for a cold, a bad case of the flu or a reaction to a hard day, especially because symptoms often ease when the dust is gone. That pattern is itself useful information for a clinician.

What exposures are involved?

The usual setting is handling moldy or poorly cured forage and grain, particularly in closed spaces. Opening old bales, cleaning bins and working in humid, dusty storage are common examples.

Other organic dusts can also cause similar reactions, so tell your provider everything you work around.

It can help to think of exposure in terms of the space as well as the material. A small closed loft full of old hay is a very different situation than moving fresh bales outdoors in a breeze.

• Moldy hay and straw
• Spoiled silage or damp grain
• Dusty feed and bedding
• Poorly ventilated barns or lofts

How is it diagnosed and treated?

A provider will ask about your symptoms and your work, and may order breathing tests, imaging or other evaluation. Treatment decisions are medical and individual, so follow your clinician's advice rather than any general rule.

A central point in medical guidance is avoiding further exposure to whatever triggered the reaction. Discuss with your provider what that means for your job, and ask about referral to a lung specialist if needed.

Ask your provider whether to avoid specific tasks and what safe alternatives exist, such as hiring help for bin or loft cleanouts. Your own situation, not a general rule, guides these choices.

How can you lower your risk?

Prevention starts with keeping crops dry and properly stored so mold does not develop, fixing leaks, and improving airflow in buildings. Avoid handling visibly moldy material when possible and plan unavoidable jobs carefully.

When dust cannot be avoided, a properly selected and fitted respirator is one layer of protection. See OSHA and NIOSH for respirator guidance and your extension office for storage practices.

If your operation hires seasonal help, make sure those workers learn the same warning signs and know where to get medical care.

Who is most at risk?

Anyone who regularly handles organic dusts in enclosed spaces can be affected, including family members who help with chores. Not everyone exposed develops the condition, and researchers do not fully predict who will, so take symptoms seriously regardless of how others around you feel.

Tell your provider if you have had repeated episodes, and mention farm work in any medical visit about breathing.

Families can help by noticing when a loved one coughs after barn work and encouraging a check-up. Talking early is easier than managing advanced lung problems.

What should you do right now if you are unwell?

If you have trouble breathing, chest pain, blue or gray lips or confusion, call 911. For milder but recurring symptoms, make an appointment and describe the pattern, including the tasks that came before it.

Keep a simple note of when symptoms start and what you were doing. It can help your provider connect the dots.

Be honest with your provider about farm tasks, including cleaning out bins, handling old hay and working in poultry or swine buildings.

Last reviewed: November 12, 2026. Written by the Farm Safety Editorial Team. See our editorial policy.