What is pneumonitis?
Pneumonitis refers to lung inflammation from non-infectious causes, for example, chemical pneumonitis or hypersensitivity pneumonitis after inhalation of irritant gases, drug-induced and radiation-induced pneumonitis .
Lung inflammation caused by microbes is called pneumonia.
Symptoms of acute pneumonitis can develop within few minutes to several hours after exposure to an irritant and may include [2,12,13]:
- Difficulty breathing
- A dry cough
- Itchy or sore throat, low-grade fever, chills, chest tightness, nausea, headache, fatigue, muscle pain
- Frothy sputum (after aspiration of gastric acid or inhalation of detergents or kerosene)
Chronic symptoms, which may last for several months, can include a cough, finger clubbing and weight loss.
Pneumonitis is not contagious.
- Aspiration of gastric acid, vomit or activated charcoal
- Inhalation of toxic fumes
- Adverse reaction to drugs
- Chest radiation
- Connective tissue diseases (systemic lupus erythematosus)
- References: [12,13]
Chemical pneumonitis can develop after inhalation of toxic vapors and fumes from household products containing bleach and chlorine, gases produced during welding or smelting, solvents, gasoline, kerosene, pesticides, dust from grains, fertilizers or smoke from fires. Chemical pneumonitis complicated by an infection is called chemical pneumonia.
Aspiration means an inhalation of a solid or liquid material into the lungs.
Aspiration pneumonitis can develop after aspiration of saliva, gastric acid, food, vomit, activated charcoal, water (during drowning) or other foreign bodies, such as detached teeth or parts of dentures. Risk factors include impaired gag reflex, gastroesophageal reflux disease (GERD), vomiting while severely drunk or unconscious (general anesthesia), dental procedures, difficulty swallowing or impaired esophageal motility (achalasia) due to neurological disorders, and impaired immunity [10,12]. Aspiration pneumonitis complicated by an infection is called aspiration pneumonia.
“Dust pneumonia” is a term for a non-infectious lung inflammation caused by silica fiber or other irritants in the dust; it was common during the period of frequent dust storms known as Dust Bowl in the 1930s in the United States .
Lipid (Lipoid) Pneumonia or Pneumonitis
Exogenous lipid pneumonia can develop after aspiration of lipid droplets during “oil pulling” or swishing (a “detox” method), petroleum jelly, oil-based nose drops or laxatives (mineral, castor or paraffin oil) .
Endogenous lipid pneumonia or “cholesterol pneumonia” can develop after the obstruction of small airways (bronchi), in which cholesterol from the broken bronchial lining cells appears in the airways distally of the obstruction .
Pneumonitis can occur as an adverse reaction to drugs, such as amiodarone , antibiotics (nitrofurantoin), aspirin, chemotherapy (bleomycin, bortezomib, busulfan, carmustine [BCNU], cyclophosphamide, methotrexate), cocaine, gold, interferon, penicillamine, phenytoin, procarbazine, sulfasalazine and the supplement L-tryptophan [8,19].
Radiation-induced pneumonitis may develop 1-3 months after completing chest radiation for breast or lung cancer .
Hypersensitivity Pneumonitis or Extrinsic Allergic Alveolitis
Hypersensitivity pneumonitis (HP) or extrinsic allergic alveolitis is a lung inflammation that occurs in genetically predisposed individuals as an allergic reaction to repetitive inhalation of :
- Fungi (Aspergillus, Candida) in the hay, grains, malt (beer production), wood, maple bark, room humidifiers, cheese, coffee, tobacco, cotton, potatoes, grapes, mushrooms, fish feed, sausages, etc.
- Bacteria in water vapor from air-conditioning, saunas, hot tubs and sewage
- Antigens in droppings or feathers of birds, gerbils, pigeons, parakeets, ducks and rats
- Polyurethane foam, paints, varnishes, lacquers, detergents, copper sulfate
Various forms of HP can be named by circumstances in which they develop, for example, “farmer’s lung” or “bird fancier’s lung.” Farmers, gardeners and workers in wood, food and chemical industry, saunas and hot tubs are at increased risk.
Viral pneumonitis can develop as an unusually strong reaction of the body to viruses:
- H1N1 influenza virus (2009 pandemic flu) 
- Cytomegalovirus (CMV) 
- Herpes simplex and Varicella-zoster virus (chicken pox) 
Other Types of Pneumonitis
- Pneumonitis as part of systemic lupus erythematosus (SLE) 
- Atypical pneumonitis 
- Cryptogenic organizing pneumonitis 
- Bacterial pneumonitis caused by anaerobic bacteria 
- Lymphocytic interstitial pneumonitis in HIV/AIDS 
Pneumonitis in Infants and Children
- Afebrile Pneumonia Syndrome (APS) is a mild disease in infants <6 months of age.
- Children’s Interstitial Lung Disease (ChILD) is a group of diseases that affect the spaces between the air sacs.
- Necrotizing pneumonitis is a severe complication of community-acquired pneumonia in children.
When you see a person with a sudden severe shortness of breath and cough who has possibly inhaled dust or toxic fumes, move him or her away from the irritants and call an ambulance immediately.
- X-ray can reveal nonspecific patches; high-resolution CT (HRCT) is more specific .
- Other investigations: blood gases analysis, lung function tests, bronchoalveolar lavage and lung biopsy and histological examination .
- Steroids (the benefit is not clear) 
- In severe cases: oxygen, mechanical ventilation
- In infection: antibiotics or antifungals
- In lipid pneumonia: immunoglobulins 
Prognosis and Complications
Mild pneumonitis can heal spontaneously and completely in few days. Severe pneumonitis can lead to complications, such as acute respiratory distress syndrome (ARDS), pneumothorax, lung abscess or death [12,13,18].
Untreated pneumonitis can cause chronic complications :
- Chronic pneumonitis with irreversible lung scarring (pulmonary fibrosis)
- Chronic obstructive pulmonary disease (COPD)
People who are sensitive to various irritants should avoid them or at least wear protective masks.
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