Symptoms of acute hypersensitivity pneumonitis usually occur after heavy exposure to an allergen and include:

• Cough
• Fever
• Chills
• Shortness of breath
• Chest tightness
• Headache
• Body aches
• Malaise (general ill feeling)
• Feeling rundown
• Nausea

These symptoms can persist for up to 18 hours, but usually resolve once the individual is away from the allergen for a period of time. However, re-exposure to the allergen is likely to trigger symptoms again.

Symptoms of chronic hypersensitivity pneumonitis are often initially milder than in the acute form of the disease. They are more likely to appear after repeated, prolonged exposure to lower doses of an allergen. They include:

• Feeling easily winded, particularly after exertion
• Shortness of breath
• Cough
• Dry cough
• Lack of appetite
• Weight loss

Although the symptoms initially appear mild in chronic hypersensitivity pneumonitis, the hidden damage can be severe and include scarring of the lungs (fibrosis). This is a largely irreversible condition that can lead to death. More advanced symptoms of chronic hypersensitivity pneumonitis also include substantial weight loss and muscle wasting.