What does eosinophilia mean?
Eosinophilia is a medical term describing an abnormally high number of eosinophils in the blood or tissues. Eosinophils are a type of white blood cell involved chiefly in defending against parasites and in mediating allergic responses, so a raised count usually signals one of these processes. Common triggers include parasitic infections such as helminths, allergic conditions like asthma and hay fever, adverse drug reactions, and less frequently autoimmune disease or malignancy. Clinicians detect eosinophilia through routine blood counts and often use its severity to guide diagnosis, distinguishing mild allergic causes from more serious hypereosinophilic syndromes. The word derives from 'eosin', the rose-pink dye named after Eos, Greek goddess of dawn, which stains these cells vividly under the microscope. Though strictly clinical in register, eosinophilia is a precise, useful term for anyone reading laboratory results or medical literature, where its presence is a well-recognised clue pointing toward allergy, infection, or immune dysregulation.
nounThe presence of an abnormally high number of eosinophils (a type of white blood cell) in the blood or other body tissues, typically indicating an allergic reaction, parasitic infection, drug reaction, or certain other diseases.
- An abnormally elevated count of eosinophils in the peripheral blood.
- An abnormal accumulation of eosinophils in tissues or organs, such as in pulmonary or gastrointestinal eosinophilia.
"The patient's persistent cough was traced to pulmonary eosinophilia caused by an underlying parasitic infection."
"Routine bloodwork revealed a striking eosinophilia that prompted further investigation for parasites."
"Intestinal biopsies confirmed marked tissue eosinophilia consistent with eosinophilic gastroenteritis."
Rarely pluralised; the word is normally treated as uncountable, though 'eosinophilias' appears occasionally when referring to distinct syndromes or types.
"The textbook devotes a chapter to the various eosinophilias of the lung."
Named after the dawn: eosinophils take their name from Eos, the Greek goddess of sunrise, because they stain a rosy pink with the dye eosin.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of eosinophilia
Eosinophilia is built from 'eosinophil' plus the suffix '-ia' denoting a condition. 'Eosinophil' combines 'eosin' — the pink dye named after Eos, the Greek goddess of dawn, coined in the late nineteenth century by German chemist Heinrich Caro — with '-phil', from Greek 'philein', to love. The term entered English medical usage in the early twentieth century as haematologists adopted staining techniques developed by Paul Ehrlich. It shares its roots with related terms such as 'eosinophil' and 'eosin'.
Related word forms
How eosinophilia is actually used
A technical medical term used almost exclusively in clinical and scientific contexts; it is uncountable and typically qualified by location (blood, tissue) or by degree (mild, moderate, marked).
Easily confused with eosinophilia
An eosinophil is the white blood cell itself, whereas eosinophilia is the condition of having an elevated count of those cells.