This condition happens when your lungs have an allergic reaction to something you have inhaled.
‘Extrinsic’ means outside, ‘allergic’ means an extreme reaction to a substance and ‘alveolis’ means inflammation of the small air sacs of the lungs. This condition is sometimes called hypersensitivity pneumonitis.
One example is farmer’s lung, which is caused by breathing mould that grows on hay, straw and grain.
Another is bird fancier’s lung, which is caused by breathing in particles from feathers or bird droppings. Inhaling certain chemicals can be another cause.
The symptoms, including cough and breathlessness, can come on suddenly after you’ve been exposed. This is the acute form of the condition.
It often goes away if you can avoid the substance that caused the attack. But it can also develop into a longer-lasting condition that permanently scars the lungs. In this case, you may need treatment with steroids and oxygen therapy.