The component allergy chip explained — what it measures, when it's used, and what it costs in Australia. Information only, not medical advice.
ImmunoCAP ISAC (short for Immuno-Solid phase Allergy Chip) is a specialised allergy blood test. From a single small sample, it measures IgE antibodies against 112 allergen components from 48 different allergen sources at once.
It's not a routine allergy test. It's used when standard tests haven't given a clear answer, when someone reacts to many allergens, in cases of unexplained severe reactions (idiopathic anaphylaxis), or when planning allergen immunotherapy.
It's not Medicare-rebated in Australia — patients usually pay the full private cost, typically around $300–600.
When you have an allergy, your immune system makes a specific antibody called IgE against the allergen. Standard allergy tests usually measure your IgE against a whole allergen — for example, all of "peanut" or all of "grass pollen."
ImmunoCAP ISAC takes a more detailed approach. Inside a peanut, there are several different proteins. Some (like Ara h 2) are strongly linked to severe whole-body reactions. Others (like Ara h 8) usually cause only mild mouth-tingling symptoms because they break down quickly in the stomach. Knowing which specific protein you react to can change what your reaction is likely to look like — and what allergens may also be risky.
This approach is called component-resolved diagnosis. ISAC measures 112 of these individual proteins (components) at once.
ImmunoCAP ISAC is typically ordered by an immunologist or allergy specialist (sometimes a GP in consultation with one), and is generally used when:
It is not a screening test for people with mild seasonal allergies, hay fever, or a single known food allergy that's already managed well. The official Australasian Society of Clinical Immunology and Allergy (ASCIA) position is that multiplex testing without a clear clinical question is of little clinical utility.
A single blood sample is taken from a vein, the same as any other blood test. No fasting required, no special preparation needed.
The sample is sent to a specialist laboratory because the test uses a microarray "chip" — a tiny slide with 112 allergen proteins printed on it. Your IgE antibodies bind to whichever proteins they recognise, and a scanner reads the result.
Results usually take about 1–2 weeks depending on the laboratory.
The report lists each of the 112 allergen components and shows your IgE level to each, usually as a number in ISU-E (ISAC Standardised Units). Levels are typically grouped into low, moderate, high, and very high.
Critically, the report also groups results by allergen "family" — so your doctor can see patterns. For example: if you react to a protein common across many plants (called a cross-reactive protein), that explains why standard tests showed lots of positives even though only one is the real trigger.
Interpretation needs a specialist. A high number on its own doesn't always mean a clinical allergy, and a low number doesn't always rule one out — the result must be matched to your actual symptoms and history. This is why ISAC results are usually reviewed by an immunologist, not interpreted at home.
ImmunoCAP ISAC is not on the Medicare Benefits Schedule. There is no Medicare rebate. You pay the full private cost.
The cost varies between laboratories but is typically around $300–600. Some private health insurance extras cover part of this; check with your insurer before booking.
By comparison: standard single-allergen IgE blood tests are often Medicare-rebated when ordered for a clinical indication, and skin prick testing by an allergist is also partly rebated. Your GP or immunologist can advise whether ISAC is the right next step or whether targeted single tests are enough.
It's an excellent tool in the right hands, but it has real limits: