Home > Health A – Z > Hypersensitivity Pneumonitis

Hypersensitivity Pneumonitis (HP)

Hypersensitivity pneumonitis, or HP, is a disease in which the lungs become inflamed from breathing in foreign substances, such as molds, dusts, and chemicals. NIH - National Heart, Lung, and Blood Institute

Hypersensitivity Pneumonitis (HP)

Hypersensitivity pneumonitis (noo-mo-NI-tis), or HP, is a disease in which the lungs become inflamed from breathing in foreign substances, such as molds, dusts, and chemicals. These substances also are known as antigens (AN-tih-jens).

People are exposed to antigens at home, while at work, and in other settings. However, most people who breathe in these substances don't develop HP.


To understand HP, it helps to understand how the lungs work. When you breathe, air passes through your nose and mouth into your windpipe. The air then travels to your lungs' air sacs. These sacs are called alveoli (al-VEE-uhl-eye).

Small blood vessels called capillaries run through the walls of the air sacs. When air reaches the air sacs, the oxygen in the air passes through the air sac walls into the blood in the capillaries. The capillaries connect to a network of arteries and veins that move blood through... Read more about Hypersensitivity Pneumonitis

What works? Research summarized

Evidence reviews

Primary Care Management of Abnormal Uterine Bleeding [Internet]

The Vanderbilt Evidence-based practice Center systematically reviewed evidence about interventions for symptomatic abnormal uterine bleeding (AUB), both irregular and cyclic. We focused on interventions that are suitable for use in primary care practice including medical, behavioral, and complementary and alternative medicine approaches.

Drug Class Review: Atypical Antipsychotic Drugs: Final Update 3 Report [Internet]

Atypical antipsychotic agents are used to treat the symptoms of schizophrenia and bipolar disorder. The purpose of this review is to help policy makers and clinicians make informed choices about their use. Given the prominent role of drug therapy in psychiatric disease, our goal is to summarize comparative data on efficacy, effectiveness, tolerability, and safety. Ten atypical antipsychotics are currently available in the United States and Canada. Clozapine, the prototypic atypical antipsychotic, was introduced in 1989. Since then, 9 other atypical antipsychotics have been brought to market: risperidone (1993), risperidone long-acting injection (2003), olanzapine (1996), quetiapine (1997), ziprasidone (2001), aripiprazole (2002), extended-release paliperidone (2006), asenapine (2009), iloperidone (2009), and paliperidone long-acting injection (2009).

Urinary Tract Infection in Children: Diagnosis, Treatment and Long-term Management

In the past 30–50 years, the natural history of urinary tract infection (UTI) in children has changed as a result of the introduction of antibiotics and improvements in health care. This change has contributed to uncertainty about the most appropriate and effective way to diagnose and treat UTI in children and whether or not investigations and follow-up are justified.

See all (20)

Terms to know

Tiny air sacs at the end of the bronchioles (tiny branches of air tubes) in the lungs. The alveoli are where the lungs and the bloodstream exchange carbon dioxide and oxygen. Carbon dioxide in the blood passes into the lungs through the alveoli. Oxygen in the lungs passes through the alveoli into the blood.
A foreign substance that triggers the production of antibodies when it is introduced into the body.
The large air passages that lead from the trachea (windpipe) to the lungs.
One of a pair of organs in the chest that supplies the body with oxygen, and removes carbon dioxide from the body.

More about Hypersensitivity Pneumonitis

Photo of an adult

Also called: Extrinsic allergic alveolitis, Allergic alveolitis, Allergic extrinsic alveolitis, Allergic interstitial pneumonitis, Allergic pneumonitis, Extrinsic allergic bronchiolo-alveolitis, Hypersensitivity pneumonia, EAA

Other terms to know: See all 4
Alveoli, Antigens, Bronchi

Related articles:
How the Lungs Work

Keep up with systematic reviews on Hypersensitivity Pneumonitis:


PubMed Health Blog...

read all...