Eosinophils
White blood cells involved in allergic reactions and parasite defence.
Typical reference range
| Range | Unit |
|---|---|
| 0–0.5 | E9/l |
What Eosinophils measures
Eosinophils are a type of white blood cell involved in allergic responses and in the body's defense against parasites. They circulate in the bloodstream and normally make up only a small fraction of the total white cell population.
Eosinophils are reported as part of the complete blood count (CBC) differential, which breaks the white cells down into their individual types. The result is usually given both as an absolute count and as a percentage of all white blood cells. Because they represent such a small share to begin with, eosinophils are most informative when read alongside the rest of the differential and your overall clinical picture, and interpreted with a clinician rather than on their own.
What a high Eosinophils can mean
A high eosinophil count, known as eosinophilia, most commonly reflects an allergic process or a parasitic infection, and it is usually read in the context of your symptoms and the rest of the blood count.
Common triggers include allergic conditions such as asthma, hay fever, eczema, and reactions to certain medications, as well as parasitic infections, which are a frequent cause worldwide. Less commonly, a raised count can accompany certain autoimmune conditions or blood disorders, so the degree of elevation and the accompanying symptoms both matter.
- Consider it in the context of any allergy symptoms or recent exposures.
- Interpret it together with the full white cell differential, not in isolation.
- A clinician can weigh your history and decide whether any follow-up is warranted.
What a low Eosinophils can mean
A low eosinophil count is usually not a cause for concern. Because eosinophils normally make up such a small fraction of white cells, low values often carry little clinical weight on their own.
A reduced count can occur temporarily during an acute infection or with the use of steroid medications, both of which can suppress eosinophil numbers for a time. In practice, the clinical interest almost always lies in high eosinophil values rather than low ones, and a value at the low end is rarely something that needs to be chased down on its own.
- Consider it alongside the rest of the CBC rather than in isolation.
- A dip during acute illness or steroid treatment is typically an expected effect.
- Discuss what your result means for you with a clinician who knows your history.
Track your Eosinophils over time in Quanome — it reads your lab reports (PDF or photo) on your device, charts each marker against its range, and an AI coach explains what your trends mean alongside your Apple Health and DNA.