What it measures
Eosinophils are a type of white blood cell involved in allergic reactions, asthma and the body's response to parasites. The count is part of the white cell breakdown (the differential) in a full blood count.
Why people test it
- Reported with a full blood count that includes the white cell breakdown.
- Often raised in hay fever, asthma, eczema and some reactions to medicines.
- Checked when a parasite infection is suspected, for example after travel.
- Steroid medicines lower the count, which can show on a result.
Typical range
Ranges vary by lab, method and analyser, and counts can change with the seasons in people with hay fever. Your report shows the lab's own range.
Finger-prick or vein?
A vein sample is usually advised. Blood from a finger prick can clot or break up (haemolyse) in the tube, which upsets blood-count results.