Pneumonitis is an inflammation of lung tissue  due to factors other than microorganisms. Those can be radiation therapy of the chest , exposure to medications used during chemo-therapy, the inhalation of debris (e.g., animal dander), of food particles during vomiting, herbicides or fluorocarbons and some systemic diseases.
It is distinguished from pneumonia on the basis of causation as well as its manifestation since pneumonia can be described as pneumonitis combined with consolidation and exudation of lung tissue due to infection with microorganism.
- Viral infection. Measles can cause severe pneumonitis, and ribavirin has been proposed as a possible treatment. CMV is another cause.
- Radiation therapy
- Inhaling chemicals, such as sodium hydroxide
- Interstitial lung disease
- Adverse reaction to medications
- Hypersensitivity to inhaled agents
- Inhalation of spores of some species of mushroom (bronchoalveolar allergic syndrome)
- Mercury exposure
- Overexposure to chlorine
- Bronchial obstruction (obstructive pneumonitis or post-obstructive pneumonitis)
- Ascariasis (during parasite migration)
A chest X-ray or CT is necessary to differentiate between pneumonitis and pneumonia of an infectious etiology. Some degree of pulmonary fibrosis may be evident in a CT which is indicative of chronic pulmonary inflammatory processes.
Typical treatment for pneumonitis includes conservative use of corticosteroids such as a short course of oral prednisone or methylprednisolone. Inhaled corticosteroids such as fluticasone or budesonide may also be effective for reducing inflammation and preventing re-inflammation on a chronic level by suppressing inflammatory processes that may be triggered by environmental exposures such as allergens.
- Hypersensitivity pneumonitis, also known as extrinsic allergic alveolitis (EAA)
- "pneumonitis" at Dorland's Medical Dictionary
- Stedman's medical dictionary (28th ed.). Philadelphia: Lippincott Williams & Wilkins. 2006. ISBN 978-0-7817-6450-6.
- "Pneumonitis - Symptoms and causes". mayoclinic.com.
- "pneumonia" at Dorland's Medical Dictionary
- "Pneumonitis. Medical information about Pneumonitis". www.patient.co.uk.
- "Mushroom Toxicity: Background, Pathophysiology, Etiology". 6 January 2017 – via eMedicine.