Symptoms accumulate over several months and include fever, cough, difficulty breathing, wheezing, and weight loss. Individuals with chronic eosinophilic pneumonia are often misdiagnosed with asthma before the correct diagnosis is made. Eosinophilic pneumonia due to medications or environmental exposures is similar and occurs after an exposure to a known offending agent. Eosinophilic pneumonia due to parasitic infections has a similar prodrome in addition to a host of different symptoms related to the variety of underlying parasites. Eosinophilic pneumonia in the setting of cancer often develops in the context of a known diagnosis of lung cancer, cervical cancer, or other certain types of cancer. Pathophysiology
Eosinophilic pneumonia can develop in several different ways depending on the underlying cause of the disease. Eosinophils play a central role in defending the body against infection by parasites. Many diseases, such as asthma and eczema, are caused when eosinophils overreact to environmental triggers and release an excess of chemicals, e.g., cytokines and histamine. The common characteristic among different causes of eosinophilic pneumonia is eosinophil overreaction or dysfunction in the lungs. Medications and environmental exposures
Medications, substance abuse, and environmental exposures may all trigger eosinophil dysfunction. Medications such as nonsteroidal anti-inflammatory drugs (e.g., ibuprofen), nitrofurantoin, phenytoin, L-tryptophan, daptomycin and ampicillin, and drugs of abuse such as inhaled heroin and cocaine may trigger an allergic response which results in eosinophilic pneumonia. Chemicals such as sulfites, aluminum silicate, and cigarette smoke can cause eosinophilic pneumonia when inhaled.
A chest X-ray can show abnormalities anywhere, but the most specific finding is increased shadow in the periphery of the lungs, away from the heart. Differential diagnosis
This includes:

Asthma
Environmental allergic reaction
Granulomatosis with polyangiitis
Allergic bronchopulmonary aspergillosis
Churg–Strauss syndrome
Loefflers syndrome
Acute eosinophilic pneumonia
Chronic eosinophilic pneumonia (Carringtons disease)
Polyarteritis nodosa
Parasitic infections
Tropical pulmonary eosinophilia
Tuberculosis
Fungal infection
Sarcoidosis
Drug reaction with eosinophilia and systemic symptoms
Mastocytosis
Lymphoproliferative hypereosinophilic syndrome
Myeloproliferative hypereosinophilic syndrome

Treatment
When eosinophilic pneumonia is related to an illness such as cancer or parasitic infection, treatment of the underlying cause is effective in resolving the lung disease. When due to acute or chronic eosinophilic pneumonia, however, treatment with corticosteroids results in a rapid, dramatic resolution of symptoms over the course of one or two days. Either intravenous methylprednisolone or oral prednisone are most commonly used. In acute eosinophilic pneumonia, treatment is usually continued for a month after symptoms disappear and the X-ray returns to normal (usually four weeks total). In chronic eosinophilic pneumonia, treatment is usually continued for three months after symptoms disappear and the X-ray returns to normal (usually four months total). Inhaled steroids such as fluticasone have been used effectively when discontinuation of oral prednisone has resulted in relapse. Because eosinophilic pneumonia affects the lungs, individuals develop difficulty breathing. If enough of the lungs are involved, it may not be possible for a person to breathe without support. Non-invasive machines such as a bilevel positive airway pressure machine may be used. Otherwise, placement of a breathing tube into the mouth may be necessary and a ventilator may be used to help the person breathe.