Loffler Syndrome 

Updated: Apr 14, 2022
Author: Girish D Sharma, MD, FCCP, FAAP; Chief Editor: Denise Serebrisky, MD 


Practice Essentials

Löffler syndrome is a transient respiratory illness associated with blood eosinophilia and radiographic shadowing. (See the image below.) It was initially described by Löffler in 1932. In 1952, Crofton included Löffler syndrome as one of the 5 categories for conditions that cause pulmonary infiltrates with eosinophilia. The original description of Löffler syndrome listed parasitic infection with Ascaris lumbricoides as its most common cause; however, other parasitic infections and acute hypersensitivity reactions to drugs are included as etiologies for simple pulmonary eosinophilia.

Initial chest radiograph of a 54-year-old man show Initial chest radiograph of a 54-year-old man showing subtle opacity (arrows) in the right middle lung zone.

Signs and symptoms

Symptoms of Löffler syndrome are usually mild or absent and tend to spontaneously resolve after several days or, at most, after 2-3 weeks. Cough is the most common symptom among symptomatic patients.

See Presentation for more detail.


Laboratory studies

The following studies are indicated in Löffler syndrome:

  • Complete blood cell (CBC) count with differential

  • Stool examination

  • Immunoglobulin E (IgE) level
  • Analysis of sputum or gastric lavages

  • Bronchoalveolar lavage

Imaging studies

The following studies may be included in the workup:

  • Chest radiography

  • Chest computed tomography (CT) scanning

See Workup for more detail.


The minimal nature of symptoms in most patients with Löffler syndrome usually denotes that no pharmacologic therapy is required for this self-limiting condition. Surgical care is not indicated.

See Treatment and Medication for more detail.


Löffler syndrome has classically been related to the transit of parasitic organisms through the lungs during their life cycle in the human host. After ingestion of Ascaris lumbricoides eggs, larvae hatch in the intestine and penetrate the mesenteric lymphatics and venules to enter the pulmonary circulation. They lodge in the pulmonary capillaries and continue the cycle by migrating through the alveolar walls. Finally, they move up the bronchial tree and are swallowed, returning to the intestine and maturing into adult forms. This process takes approximately 10-16 days after ingestion of the eggs. Other parasites, such as Necator americanus, Ancylostoma duodenale, and Strongyloides stercoralis, have a similar cycle to Ascaris, with passage of larval forms through the alveolar walls. These parasites are not orally ingested but enter the human host through the skin.

A review of the parasitic infections of the lung provides an excellent guide for the pulmonary physician.[1]

Researchers initially thought that transit of parasitic forms through the lung was cardinal in the pathogenesis of Löffler syndrome; however, pulmonary eosinophilia has been described in association with parasites whose life cycle does not include passage through the alveoli and also in association with an increasing number of medications. Additionally, eosinophilic pulmonary infiltrates have appeared in mice challenged with a transnasal Ascaris extract. In these situations, accumulation of eosinophils in the lungs is likely secondary to immunologic hyperresponsiveness. The exact immunopathogenic mechanism for this reaction remains unknown.

Animal models demonstrated that development of pulmonary eosinophilia is T cell–dependent because challenged athymic mice do not develop pulmonary eosinophilia. Production of cytokines such as interleukin-5 (IL-5) is necessary for development of pulmonary eosinophilia. Recent data suggest that circulating, but not local, lung IL-5 is critically required for the development of antigen-induced pulmonary eosinophilia.


Most cases of simple pulmonary eosinophilia are caused by parasitic infections or drugs; however, no cause is identified in one third of patients.

Parasites that can cause pulmonary eosinophilia include the following:

  • Ascaris lumbricoides (the most common parasitic etiology)

  • Ascaris suum

  • Necator americanus

  • Strongyloides stercoralis

  • Ancylostoma braziliense

  • Ancylostoma caninum

  • Ancylostoma duodenale

  • Toxocara canis

  • Toxocara cati

  • Entamoeba histolytica

  • Fasciola hepatica

  • Dirofilaria immitis

  • Clonorchis sinensis

  • Paragonimus westermani

Agents in drug-induced eosinophilia include the following:

  • Antimicrobials - Dapsone, ethambutol, isoniazid, nitrofurantoin, penicillins, tetracyclines, clarithromycin, pyrimethamine, daptomycin[2]

  • Anticonvulsants - Carbamazepines, phenytoin, valproic acid, ethambutol

  • Anti-inflammatories and immunomodulators - Aspirin, azathioprine, beclomethasone, cromolyn, gold, methotrexate, naproxen, diclofenac, fenbufen, ibuprofen, phenylbutazone, piroxicam, tolfenamic acid

  • Other agents - Bleomycin, captopril, chlorpromazine, granulocyte-macrophage colony-stimulating factor, imipramine, methylphenidate, sulfasalazine, sulfonamides


United States statistics

Intestinal helminthiases associated with Löffler syndrome, such as ascariasis, have a reported prevalence of 20-67% among children in rural southern communities. No specific statistics have been reported for the occurrence of Löffler syndrome. Because of widespread globalization, immigration, and travel, US physicians may now more commonly encounter imported tropical diseases that may present with Löffler syndrome.

International statistics

Intestinal helminthiases associated with Löffler syndrome are distributed worldwide; however, they are more prevalent in tropical climates, especially in communities with poor sanitary conditions.

Age-related demographics

Because young children are exposed to contaminated soil and exhibit hand-to-mouth behavior more often than adults, they have a higher incidence of intestinal helminthiases and Löffler syndrome.


Prognosis is excellent.


No deaths due to Löffler syndrome have been reported. Löffler syndrome is considered a benign, self-limiting disease without significant morbidity. Symptoms usually subside within 3-4 weeks or shortly after the offending medication is withdrawn in drug-induced pulmonary eosinophilia.


A case report describes hypereosinophilic syndrome with isolated Loeffler endocarditis, which resolved completely after 2 months of corticosteroid therapy.[3]

Patient Education

Sanitary practice

Educate people about sanitary disposal of feces, associated with educational campaigns for the use of latrines and pit privies in rural communities.

Promote good handwashing technique to avoid ingestion of parasitic forms from contaminated soil.


In endemic areas of ancylostomiasis and strongyloidiasis, encourage use of proper footwear to avoid skin penetration of larvae of N americanus, A duodenale, or S stercoralis.

Avoid future use of the offending medication in patients with drug-induced pulmonary eosinophilia.




Symptoms of Löffler syndrome are usually mild or absent and tend to spontaneously resolve after several days or, at most, after 2-3 weeks. Cough is the most common symptom among symptomatic patients. It is usually dry and unproductive but may be associated with production of small amounts of mucoid sputum.

Parasitic infection

Symptoms appear 10-16 days after ingestion of Ascaris eggs. A similar timeframe has been described for Löffler syndrome associated with N americanus, A duodenale, or S stercoralis infection.

Fever, malaise, cough, wheezing, and dyspnea are the most common symptoms. Less commonly, the patient may present with myalgia, anorexia, and urticaria.

A Turkish case report describes a 5-year-old boy with Löffler syndrome caused by A lumbricoides, who initially presented with a 3-day history of cough, dyspnea, wheezing, and intermittent fever.[4]

Social and travel history should be carefully elicited to identify risk factors for exposure to parasites.

Drug-induced pulmonary eosinophilia

Symptoms may start hours after taking the medications or, more commonly, after several days of therapy. Dry cough, breathlessness, and fever are common.[5, 6]

Obtain a detailed drug history, including prescription and over-the-counter medications, nutritional supplements, and illicit drugs.

Physical Examination

Usually, no abnormalities are found on physical examination. Cutaneous features of hypereosinophilic syndrome are described in a review article.[7]

Occasionally, crackles or wheezes may be heard on lung auscultation. Patients with drug-induced pulmonary eosinophilia commonly have crackles on physical examination.



Differential Diagnoses



Laboratory Studies

The following studies are indicated in Löffler syndrome:

  • CBC count with differential

    • Results show mild blood eosinophilia, usually 5-20%.

    • Eosinophils may account for as much as 40% of the WBC differential in patients with drug-induced eosinophilia.

  • Stool examination

    • Parasites and ova can be found in the stool 6-12 weeks after the initial parasitic infection.

    • Pulmonary symptoms usually resolve by the time parasitic forms are found in the stool.

  • Immunoglobulin E (IgE) level: This may be elevated.

  • Analysis of sputum or gastric lavages: Larvae are occasionally found in sputum and gastric aspirates at the time of pulmonary symptoms.

  • Bronchoalveolar lavage: The eosinophilic count may be elevated.

Imaging Studies

Chest radiography

Roentgenographic abnormalities can be unilateral or bilateral.

Most patients have peripheral densities, usually of a combined interstitial and alveolar pattern and often a few centimeters in diameter, although they may coalesce into larger areas of consolidation.

Densities are generally transient, migratory, and disappear completely within 2-4 weeks.

In drug-induced pulmonary eosinophilia, radiographic abnormalities resolve completely several weeks after withdrawal of the offending drug.

Pleural effusions may be present in patients with nitrofurantoin toxicity. A case of eosinophilic pleural effusion with peripheral blood eosinophilia has been described with valproic acid administration.

Initial chest radiograph of a 54-year-old man show Initial chest radiograph of a 54-year-old man showing subtle opacity (arrows) in the right middle lung zone.
Follow-up chest radiograph of a 54-year-old man sh Follow-up chest radiograph of a 54-year-old man showing migrating opacity in the left lower lobe (arrows) obtained 20 days after the previous image.

Chest CT scanning

One report describes areas of ground-glass opacity (halo) around consolidation or nodules observed on high-resolution chest CT scanning. See the image below.

High-resolution CT scan (1 mm collimation) obtaine High-resolution CT scan (1 mm collimation) obtained in a 54-year-old man showing consolidation with surrounding ground-glass opacity in the left lower lobe. Dilated airways are observed within the lesion. This CT scan was obtained between the first and second images above.


Bronchoscopy and bronchoalveolar lavage are rarely indicated. In one report, the total number of cells found in bronchoalveolar lavage fluid (BALF) from patients with drug-induced pulmonary eosinophilia was significantly elevated compared to healthy subjects. Specifically, the number of lymphocytes and eosinophils in BALF was higher than in healthy subjects. These findings were not specific for drug-induced pulmonary eosinophilia because similar numbers were found in patients with chronic eosinophilic pneumonia. In addition to elevated eosinophils and lymphocytes in BALF, patients with acute eosinophilic pneumonia had high numbers of neutrophils in BALF.

Histologic Findings

Pathologic changes in the lungs have been described in patients who died from another cause while they concomitantly had simple pulmonary eosinophilia.

Eosinophilic infiltration occurs in the bronchi and bronchioles and in the alveolar and interstitial spaces. Parasitic forms are usually not found in the lungs.



Approach Considerations

Evaluation of Löffler syndrome can be conducted on an outpatient basis; inpatient care is not required.[8]

Surgical care is not indicated.

Consider consultation with a pediatric pulmonologist.

Diet and activity

No special diet is required.

No activity limitation is indicated.



Medication Summary

The minimal nature of symptoms in most patients with Löffler syndrome usually denotes that no pharmacologic therapy is required for this self-limiting condition. For drug-induced pulmonary eosinophilia, discontinue administration of the offending drug. When a parasitic infection is documented, appropriate use of anthelmintic drugs is indicated. In severe cases of simple pulmonary or drug-induced eosinophilia, systemic corticosteroids are highly effective.


Class Summary

Markedly reduce the survival of certain inflammatory cells, including eosinophils. Eosinophil survival is dependent on the presence of certain cytokines (eg, interleukin-5 [IL-5], granulocyte macrophage colony stimulating factor and [GM-CSF]), whose effects are blocked by administration of corticosteroids.

Prednisone (Deltasone, Meticorten, Orasone, Sterapred)

May decrease inflammation by reversing increased capillary permeability and suppressing PMN activity.



Further Outpatient Care

Repeat chest radiography 4-6 weeks after initial presentation to document resolution of pulmonary infiltrates in patients with Löffler syndrome.

Repeat CBC count 4-6 weeks after initial presentation to document resolution of eosinophilia.

Examine stool for ova and parasites 6-12 weeks after initial presentation.

Inpatient & Outpatient Medications

Use appropriate antihelminthic therapy if parasitic infection is diagnosed.

Use systemic corticosteroids for patients with severe respiratory symptoms.