Any particles that are smaller than 5 microns can enter the alveoli of the lungs. These tiny air sacs facilitate the passage of oxygen from inhaled air to the bloodstream. In the case of pneumonitis, it is more difficult for this exchange of oxygen to occur since irritants have caused inflammation of the alveoli. Due to the lack of a definitive determination of a single irritant causing pneumonitis, there are several possible causes. Viral infection. Measles can cause severe pneumonitis, and ribavirin has been proposed as a possible treatment. CMV is another cause. Pneumonia
Radiation therapy
Inhaling chemicals, such as sodium hydroxide
Interstitial lung disease
Sepsis
Adverse reaction to medications
Hypersensitivity to inhaled agents
Inhalation of spores of some species of mushroom (bronchoalveolar allergic syndrome)
Mercury exposure
Smoking
Overexposure to chlorine
Bronchial obstruction (obstructive pneumonitis or post-obstructive pneumonitis)
Ascariasis (during parasite migration)
Aspirin overdose, some antibiotics, and chemotherapy drugs
“Farmer’s lung” and “hot tub lung” are common names for types of hypersensitivity pneumonitis that result from exposure to some types of thermophilic actinomyces, mycobacteria and molds. Avian proteins in bird feces and feathers 
Whole body or chest radiation therapy used for cancer treatment

Symptoms
Physical manifestations of Pneumonitis range from mild cold-like symptoms to respiratory failure. Most frequently, those with pneumonitis experience shortness of breath, and sometimes a dry cough.
Neurosis is a class of functional mental disorders involving chronic distress, but neither delusions nor hallucinations. The term is no longer used by the professional psychiatric community in the United States, having been eliminated from the Diagnostic and Statistical Manual of Mental Disorders (DSM) in 1980 with the publication of DSM III. However, it is still used in the ICD-10 Chapter V F40–48. Neurosis should not be mistaken for psychosis, which refers to a loss of touch with reality. Nor should it be mistaken for neuroticism, a fundamental personality trait proposed in the Big Five personality traits theory. Etymology
The term is derived from the Greek word neuron (νεῦρον, nerve) and the suffix -osis (-ωσις, diseased or abnormal condition). The term neurosis was coined by Scottish doctor William Cullen in 1769 to refer to "disorders of sense and motion" caused by a "general affection of the nervous system." Cullen used the term to describe various nervous disorders and symptoms that could not be explained physiologically. Physical features, however, were almost inevitably present, and physical diagnostic tests, such as exaggerated knee-jerks, loss of the gag reflex and dermatographia, were used into the 20th century. The meaning of the term was redefined by Carl Jung and Sigmund Freud over the early and middle 20th century, and has continued to be used in psychology and philosophy.The Diagnostic and Statistical Manual of Mental Disorders (DSM) eliminated the neurosis category in 1980, because of a decision by its editors to provide descriptions of behavior rather than descriptions of hidden psychological mechanisms.