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Diseases A–Z

Farmer’s lung

Symptoms | Treatment | How to avoid mouldy hay

Farmer's Lung is a disease caused by breathing in spores from mouldy hay. It affects people who work with hay a lot. Over time, certain people can become allergic to the mould in hay. The symptoms are serious, and once the allergic reaction begins, the person will always have the potential for symptoms when they're exposed to hay mould.

What causes farmer's lung?

Farmer's lung is caused by being exposed to hay mould spores, especially in a closed space without good ventilation — such as a barn in the winter. It is not the hay itself that makes people sick — it's the mould that grows in baled hay that causes farmer's lung.

What are the symptoms of farmer's lung?

After working with mouldy hay for several months or years, depending on the individual, the worker may begin to notice the following symptoms four to six hours after being exposed to the hay mould spores:

  • increased coughing and bringing up more mucus (phlegm) than usual
  • fever and sometimes chills
  • feeling short of breath
  • discomfort in the lungs, a tightness and/or pains in the chest

The symptoms of farmer's lung are similar to those of other lung diseases. If you have these symptoms, or if you think you have farmer's lung, see you doctor for a proper diagnosis.

Who is at risk of farmer's lung?

Anyone who is allergic to the hay mould spores and breathes air filled with hay mould spores.

How is farmer's lung treated?

The main treatment is to stay totally away from hay mould spores. Medication may help your symptoms, but you can't completely get rid of your symptoms if you still spend time near mouldy hay.

How to avoid mouldy hay
  • Use a milking parlour to keep feeding separate, and get someone else to feed the herd.
  • Use a free stall or open barn system along with excellent barn ventilation.
  • Feed haylage (a fermented animal feed).
  • Use mould inhibitors.
  • Get out of farming. May help, but not foolproof; each farmer's solution must be individualized.
Why do farmers who are allergic to hay mould feel worse in the winters?

In the winter, farmers feed baled hay inside. When the hay bales are stored inside, the mould has a better chance to grow and the mould spores are trapped inside the air in the barn.

What happens if a person with farmer's lung continues to be near mouldy hay?

A person with farmer's lung who does not avoid hay mould may get sicker and sicker until they are no longer able to do hard work. After many years, people with farmer's lung may not be able to be active at all. People can die from farmer's lung.

If you think you have farmer's lung

See your doctor. Tell the doctor your symptoms. Some doctors may not be very familiar with the disease, so it may be necessary for your doctor to refer you to a specialist.

A blood test, a chest X-ray and a breathing capacity test are some of the procedures that will be necessary in order to make sure that the disease is farmer's lung. Other tests may be needed as well.

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