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What Are the Signs and Symptoms of Hypersensitivity Pneumonitis?

Signs and symptoms of hypersensitivity pneumonitis (HP) depend on whether the disease is acute (short-term) or chronic (ongoing).

Acute Hypersensitivity Pneumonitis

With acute HP, symptoms usually occur within 2–9 hours of exposure to an antigen you're sensitive to. (An antigen is a substance that your body reacts against, such as molds, dusts, and chemicals.)

Acute HP can cause chills, body aches, coughing, and chest tightness. After hours or days of no contact with the antigen, symptoms usually go away.

Chronic Hypersensitivity Pneumonitis

If acute HP isn't found and treated early, chronic HP may develop. With chronic HP, symptoms occur slowly, over months. Chronic HP can cause a worsening cough, shortness of breath with physical activity, fatigue (tiredness), and weight loss.

Some symptoms may continue and/or worsen, even after avoiding the antigen. Chronic HP can cause long-term lung damage, such as pulmonary fibrosis. This is a condition in which tissue deep in your lungs becomes scarred over time.

Clubbing also may occur if HP is severe. Clubbing is the widening and rounding of the tips of the fingers or toes. A low level of oxygen in the blood causes this condition.

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Hypersensitivity Pneumonitis Clinical Trials

Clinical trials are research studies that explore whether a medical strategy, treatment, or device is safe and effective for humans. To find clinical trials that are currently underway for Hypersensitivity Pneumonitis, visit

May 09, 2014 Last Updated Icon

The NHLBI updates Health Topics articles on a biennial cycle based on a thorough review of research findings and new literature. The articles also are updated as needed if important new research is published. The date on each Health Topics article reflects when the content was originally posted or last revised.