Aetiology

Eosinophilia is commonly due to allergic diseases, parasitic infection, drug reactions, or skin disease. Rare causes include malignancy, gastrointestinal disorders, connective tissue diseases, immune deficiency states, hereditary eosinophilia, and cyclical eosinophilia with angio-oedema.[3][4]

Parasitic infestations

Many parasitic infestations can result in eosinophilia, particularly strongyloidiasis, schistosomiasis, filariasis, trichinellosis, toxocariasis, fasciolopsiasis, muscular sarcocystosis, Cystoisospora belli (formerly Isospora belli) infection, anisakiasis, and loiasis.[5]​

Allergic diseases

Allergic diseases, such as asthma or allergic rhinitis, are usually apparent from the history.

Drug reactions

Hypersensitivity to many drugs, including carbamazepine, allopurinol, sulfonamides, penicillin, phenytoin, and gold, may cause eosinophilia.

Skin diseases

Possible skin diseases are pemphigus, bullous pemphigoid, and pemphigoid gestationis.

Immune deficiency syndromes

Possible aetiologies include Wiskott-Aldrich syndrome, Job's syndrome, hyperimmunoglobulin E syndrome, severe combined immune deficiency due to adenosine deaminase deficiency, and Omenn's syndrome.[6][7]​[8]​​

Immune dysregulation

The possible aetiologies are: immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome; autoimmune lymphoproliferative syndrome (ALPS); Loeys-Dietz syndrome; Comel-Netherton syndrome; and severe dermatitis, multiple allergies, and metabolic wasting (SAM) syndrome.[8]​

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