Eosinophilia

Definition

Eosinophilia is defined as an elevation of the eosinophil count above 0.4 x10⁹/L. The initial step in the evaluation of eosinophilia is to rule out reactive (secondary) causes.

The most common causes of eosinophilia are allergy, eczema/asthma, drug-induced and parasitic infections.

After reactive causes have been ruled out, the patient may be referred to Haematology for investigation of clonal eosinophilia.

Who to refer, who not to refer, how to refer

Who to refer:

Patients with significant persistent eosinophilia (≥ 1.5 x 10⁹/L) without obvious underlying reactive cause.

Who not to refer:

Reactive eosinophilia – the patient may require assessment by other specialties, e.g. Rheumatology, Dermatology, Infectious Disease, Respiratory Medicine depending on symptoms
Patients with persistent unexplained mild to moderate eosinophilia (0.4-1.4 x10⁹/L) can be given a diagnosis of idiopathic eosinophilia once secondary causes have been excluded.

Please see Primary Care Management for initial investigative approaches.

How to refer:

SCI Gateway to the Department of Haematology BGH

Primary care management

Primary care investigations

Look for underlying causes such as

Allergic disorders such as atopic eczema, asthma, hay fever
Drugs
Parasites
Vasculitis (e.g. eosinophilic granulomatosis with polyangiitis)
Allergic bronchopulmonary aspergillosis
Malignancy
Hodgkin lymphoma.

Investigations:

FBC + film
CRP
U&E, LFT, LDH
Stools x 3 for ova, cysts and parasites
Repeat FBC at 3 months.

Resources and links

Guideline for the investigation and management of eosinophilia – Butt – 2017 – British Journal of Haematology – Wiley Online Library

Last reviewed: 17/01/2025

Next review date: 17/01/2027

Author(s): Charlotte Robertson.