Pneumonitis or pulmonitis is a general term that refers to inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

 of lung

Lung

The lung is the essential respiration organ in many air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located near the backbone on either side of the heart...

 tissue.

Pneumonia

Pneumonia

Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

 is pneumonitis combined with consolidation and exudation

Exudate

An exudate is any fluid that filters from the circulatory system into lesions or areas of inflammation. It can apply to plants as well as animals. Its composition varies but generally includes water and the dissolved solutes of the main circulatory fluid such as sap or blood...

. Many factors can cause pneumonitis, including breathing in animal dander

Dander

Dander is an informal term for a material shed from the body of various animals, similar to dandruff. It may contain scales of dried skin and hair, or feathers. It is a cause of allergies in humans....

, inhaling small food particles "down the wrong pipe", and receiving radiation therapy

Radiation therapy

Radiation therapy , radiation oncology, or radiotherapy , sometimes abbreviated to XRT or DXT, is the medical use of ionizing radiation, generally as part of cancer treatment to control malignant cells.Radiation therapy is commonly applied to the cancerous tumor because of its ability to control...

 to the chest.

Classification

It can be classified into acute interstitial pneumonitis, blood pneumonitis, lymphocytic interstitial pneumonitis, radiation pneumonitis, and uremic pneumonitis.

Causes

• Viral infection
  Virus
  A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
  
  . As one example, measles
  Measles
  Measles, also known as rubeola or morbilli, is an infection of the respiratory system caused by a virus, specifically a paramyxovirus of the genus Morbillivirus. Morbilliviruses, like other paramyxoviruses, are enveloped, single-stranded, negative-sense RNA viruses...
  
   can cause severe pneumonitis, and ribavirin
  Ribavirin
  Ribavirin is an anti-viral drug indicated for severe RSV infection , hepatitis C infection and other viral infections. Ribavirin is a prodrug, which when metabolised resembles purine RNA nucleotides...
  
   has been proposed as a possible treatment.
• Pneumonia
  Pneumonia
  Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
  
  
• Radiation therapy
• Inhaling chemicals, such as Sodium hydroxide
• Sepsis
  Sepsis
  Sepsis is a potentially deadly medical condition that is characterized by a whole-body inflammatory state and the presence of a known or suspected infection. The body may develop this inflammatory response by the immune system to microbes in the blood, urine, lungs, skin, or other tissues...
  
  
• Adverse reaction to medications
• Hypersensitivity to inhaled agents
• Inhalation of spores of some species of mushroom
  Lycoperdon
  Lycoperdon is a genus of puffball mushrooms. The genus has a widespread distribution and contains about 50 species. In general, it contains the smaller species such as the pear shaped puffball and the gem studded puffball. Most of the time they grow from dead wood and if they grow through the...
  
   (Bronchoalveolar allergic syndrome)
• Mercury
  Mercury (element)
  Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
  
   exposure
• Smoking
  Smoking
  Smoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them...
  
  
• Overexposure to Chlorine