Finding the right tests…
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Finding the right tests…
Haematology
AEC counts a single white blood cell type: eosinophils, the cells your body raises against parasites and certain allergic reactions. A normal count sits under 500 cells per microlitre of blood; by percentage alone, eosinophils normally make up just 1 to 4 percent of all white cells. This test is ordered by itself - not as part of a fresh full blood count - when a doctor is already following a known allergic condition, a suspected parasite infection, or a drug reaction, and wants to see whether the number is climbing or settling. Like the neutrophil count, it is calculated: the white cell total multiplied by the eosinophil percentage from the differential.
The result is reported as cells per microlitre, not as a percentage of total white cells - a count rather than a share. It comes from the same blood draw as a differential count, so no extra sample is usually needed if one was drawn recently. Because eosinophil numbers respond within days to steroids, antihistamines or antiparasitic treatment, repeat testing over a short window is how a doctor tells whether a reaction or infection is settling.
Eosinophils rise with allergic disease such as asthma or eczema, with some skin conditions, with parasitic infections, and with a small group of blood disorders. A single high reading on its own does not point to one specific cause - it narrows the search rather than closing it.
Once your doctor already suspects an allergic or parasitic cause, or is treating one of the rarer eosinophil-driven conditions, repeating the whole white cell differential adds little. Following just this one number over several visits shows whether treatment is working, without the turnaround time of a fresh full differential each time.
- Following a known allergic or eczema flare - Checking for parasite infection when symptoms suggest one - Monitoring hypereosinophilic syndrome or a related blood disorder - Tracking a suspected drug reaction
A high result needs your doctor's interpretation alongside your symptoms, travel history and current medicines - the count alone cannot say whether the cause is allergy, infection or something else. Bring your recent medication list when you discuss the result.
A normal absolute eosinophil count is generally under 500 cells per microlitre of blood. Ranges vary by lab, so check the reference range printed on your own report rather than relying on a single number.
Not necessarily. Allergic conditions like asthma, eczema and hay fever raise eosinophils just as commonly as parasite infections do. The test on its own cannot tell the two apart, so your doctor looks at your symptoms and history alongside it.
Yes. Asthma, eczema, hay fever and drug allergies are all common causes of a raised eosinophil count, often without any parasite involved at all.
It is calculated from the same differential count that's part of a complete blood count. It is usually reported separately as its own value, though, especially when a doctor is tracking it on repeat visits.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
AEC isolates just the eosinophil line. A DLC reports the percentage of every white cell type - neutrophils, lymphocytes, monocytes, eosinophils and basophils - together, giving a broader picture rather than following one type alone.
Yes. Corticosteroids in particular can push the count down quickly, which is one reason your doctor may ask what medicines you're taking before interpreting a low result.