Patient guide · Allergy and immunology
Allergy blood tests, specific IgE testing for food, environmental and drug allergens.
Blood-based allergy testing (specific IgE / ImmunoCAP) measures antibodies to specific allergens. A safe alternative to skin-prick testing — useful for patients on antihistamines, with eczema, or when skin testing is contraindicated.
Why patients choose us
- 01
The right hands
We route you to a consultant allergist — the person who chooses the panel and interprets the results decides the answer.
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Often answers within a week
Results usually return within 5–7 working days, with a structured plan to follow.
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Independent, and free
We are paid by no clinic, so the recommendation is impartial and costs you nothing.
Key facts
What allergy blood tests actually measure.
Specific IgE testing is a laboratory measurement — a number per allergen. The clinical meaning comes from your history.
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Definition
A blood test measuring specific IgE antibodies to individual allergens.
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ImmunoCAP is the gold-standard assay
The reference method used by allergy specialists worldwide.
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Panels for foods, aeroallergens, drugs, insect venom
A single sample can be tested against multiple targeted panels.
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Not affected by antihistamines
A useful alternative when skin-prick testing is not possible.
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Positive test ≠ allergy
Results are always interpreted alongside a detailed clinical history.
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Component-resolved diagnostics (CRD)
CRD improves diagnostic accuracy in food allergy — particularly peanut, tree nut and wheat.
The problem
A specific IgE test is only as good as the panel — and the reader.
Broad, untargeted screens generate false positives that push patients into needless avoidance. A consultant allergist chooses the panel against the history and interprets the numbers alongside it.
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Suspected food allergy?
We build a targeted panel — with component-resolved diagnostics where risk stratification matters.
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Rhinitis, eczema or asthma?
We test aeroallergens that map to your symptoms — and set out avoidance and immunotherapy options.
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Drug or venom reaction?
We work up specific IgE with a clear plan — including supervised challenge or immunotherapy where indicated.
Preparation and pathway
From history to plan — what happens, in order.
One clinician from history-taking to interpretation — usually within a week.
Phase 1 · Before your test
History, panel choice, blood draw
Phase 2 · Laboratory
ImmunoCAP analysis, 5–7 days
Phase 3 · Interpretation
Consultant review and plan
- 01
Before
Detailed allergy history
A structured history — symptoms, timing, triggers, medications and prior reactions — guides the panel.
- 02
Before
Choose targeted panel
Panels are chosen against symptoms, not tested at random. Broad, untargeted screens generate false positives.
- 03
Before
Blood draw — single sample
One venous sample. No fasting. Antihistamines can be continued.
- 04
Laboratory
ImmunoCAP laboratory analysis
Specific IgE quantified against each allergen using ImmunoCAP or an equivalent validated assay.
- 05
Laboratory
Results within 5–7 working days
Numerical specific IgE values are returned per allergen, with component-resolved data where relevant.
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After
Consultant allergist interpretation
Numbers are set against your history — sensitisation is not the same as clinical allergy.
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After
Structured plan
Avoidance, rescue medication, and — where appropriate — immunotherapy referral or supervised food challenge.
Typical end-to-end: 7–10 days from consultation to structured plan.
What it shows
What allergy blood testing can — and can’t — answer.
Specific IgE answers a specific question — is there sensitisation to this allergen — and to what degree. Clinical allergy is the judgement built on top.
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Specific IgE to individual allergens
Quantifies IgE against each targeted allergen — the core output of the test.
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Cross-reactivity patterns
Identifies related sensitisations (e.g. birch–apple, latex–fruit) that shape avoidance advice.
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Component-resolved diagnostics (peanut, tree nut, wheat)
Distinguishes high-risk components (e.g. Ara h 2) from cross-reactive proteins with lower risk.
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Total IgE level
Baseline IgE, useful in atopy assessment and for interpreting specific IgE values.
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Insect venom sensitisation
Bee and wasp specific IgE, key when systemic reactions have occurred.
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Drug allergy screening
Specific IgE for selected drugs (e.g. penicillin, chlorhexidine) — a starting point, not a rule-out.
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Aeroallergen sensitisation
Grass and tree pollens, house dust mite, cat, dog and mould — drives rhinitis and asthma plans.
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Red flag: high-risk food component + anaphylaxis history — supervised food challenge only
Never home-test suspected foods. Challenges are performed in a supervised setting with resuscitation on hand.
Next steps
Turning a result into a plan.
What can — and should — happen once the specific IgE values are in.
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Allergen avoidance plan
A written, practical avoidance plan built around your daily life — food labels, cross-contamination, environmental triggers.
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Adrenaline auto-injector prescription
Where anaphylaxis risk is identified, prescription and training in device technique.
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Antihistamines and nasal steroids
First-line symptomatic treatment for rhinitis, urticaria and mild reactions.
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Asthma optimisation
Where atopic asthma coexists, inhaler technique and controller therapy are reviewed.
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Immunotherapy referral (SLIT / SCIT)
Sublingual or subcutaneous immunotherapy for selected aeroallergen and venom cases.
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Supervised oral food challenge
The definitive test for suspected food allergy where blood and history are inconclusive.
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Drug provocation testing (specialist)
Graded challenge in a supervised specialist setting for suspected drug allergy.
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Follow-up with allergist
Structured review to reassess sensitisations, escalate or step down therapy.
Our vetted London network
A small panel of allergists, we picked them.
Consultant allergists across London — introductions made privately, once we understand your case.
Selection criteria
How we choose every allergist in our network.
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Consultant allergists (BSACI-registered)
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ImmunoCAP or equivalent validated specific IgE assays
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Component-resolved diagnostics available where clinically indicated
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Onward pathway to immunotherapy or supervised challenge if required
Red flags
When results must be handled by a specialist.
The patterns below change management. They are the reason interpretation belongs with a consultant allergist, not with a numerical printout.
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Anaphylaxis history
A prior anaphylaxis reaction is the single most important item in the history — it drives everything from panel choice to prescription.
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High-risk food component (e.g. Ara h 2 for peanut)
Component-resolved diagnostics flag proteins associated with severe reactions rather than benign cross-reactivity.
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Insect venom allergy with systemic reaction
Systemic reactions to bee or wasp stings warrant specialist review and, in most cases, venom immunotherapy discussion.
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Drug allergy with hypersensitivity syndrome
DRESS, SJS/TEN and AGEP are severe reactions — blood testing is only one part of a specialist work-up.
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Latex allergy in healthcare workers
Occupational latex sensitisation carries workplace and surgical implications and warrants specialist review.
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Occupational allergy
Bakers’ asthma, healthcare glove reactions and laboratory animal allergies each need targeted panels and occupational input.
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Idiopathic anaphylaxis
Where triggers are not identified, mastocytosis and food-dependent exercise-induced anaphylaxis are considered.
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Systemic mastocytosis differential
Baseline tryptase and mast-cell disease should be considered in recurrent unexplained anaphylaxis.
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Food-dependent exercise-induced anaphylaxis
Wheat (omega-5 gliadin) and other foods can trigger anaphylaxis only in combination with exercise — a specific pattern to recognise.
Reading your report
An allergy report can look intimidating. It isn’t.
Whatever the finding, the report keeps to the same four parts.
A quiet reminder
The report is written for your doctor, not for you — and that’s normal.
If you would like us to talk you through it before your follow-up, just ask.
- 01 Header
Indication and history summary
Your details, the reason for testing, and the clinical history that shapes interpretation.
- 02 Panel
Allergens tested and assay used
The panel selected, the assay (ImmunoCAP or equivalent), and any component-resolved diagnostics performed.
- 03 Findings
Specific IgE values per allergen
Quantitative specific IgE (kUA/L) for each allergen, with component values where measured, and total IgE.
- 04 Impression
The conclusion: read this first
What is sensitisation vs likely clinical allergy, the risk profile, and the concrete next step.
Recognised by major UK insurers
Cover depends on your policy and clinic; we confirm with your insurer before booking.
Frequently asked
Everything we get asked about allergy blood tests.
Quick answers on accuracy, antihistamines, component-resolved diagnostics, panel size and when a supervised food challenge is needed.
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What does an allergy blood test show?
It measures specific IgE antibodies against individual allergens. High values suggest sensitisation, but sensitisation is not the same as clinical allergy — the result must be interpreted alongside your history.
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Is it as accurate as skin-prick testing?
For most allergens, specific IgE and skin-prick testing are comparably accurate. Blood testing is preferred when antihistamines cannot be stopped, when eczema covers the test area, or when skin-prick testing is contraindicated.
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Do I need to stop antihistamines?
No. Blood tests are unaffected by antihistamines, which is one of the main reasons they are chosen over skin-prick testing.
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What is component-resolved diagnostics (CRD)?
CRD measures IgE against individual proteins within an allergen (e.g. Ara h 2 in peanut). It helps distinguish high-risk sensitisation from benign cross-reactivity, particularly for peanut, tree nut and wheat.
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Can I test for many allergens at once?
Yes — but broad, untargeted panels generate false positives and lead to unnecessary avoidance. Targeted panels chosen against the history are more useful.
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When would I need a supervised food challenge?
When blood testing and history are inconclusive, an oral food challenge under specialist supervision is the definitive test. It is never performed at home.
Sources
Clinical references.
- British Society for Allergy and Clinical Immunology (BSACI). Clinical guidelines.
- NICE. Anaphylaxis and allergy guidance.
- EAACI molecular allergology user’s guide.
- Royal College of Pathologists. Standards for allergy testing.
Last reviewed 2026-07-30 · Next review 2027-07-30 · Reviewed by Pulse Atlas Editorial Board, .
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In practice, in London
The London pathway for allergy blood tests
With allergy blood tests, the London question is usually about report turnaround and the radiologist reading it — not whether the scan is available. The wait for allergy blood tests on the NHS depends heavily on where you live and how urgently the referral is graded. Central and West London private clinics can normally book within a week, with imaging or a procedure slot to follow shortly after. It’s worth being honest about the reason for going private: usually it’s time, not a fundamentally different test.
In practice, a private allergy blood tests appointment in London means a named consultant, a proper hour in the room (or the equivalent on a video call), and a report you can actually read. Most of the imaging suites and endoscopy units we use sit within a mile of Harley Street or in Chelsea and Fulham, and turnaround on findings is measured in days, not weeks. For allergy blood tests specifically, the difference between a routine report and a sub-speciality read is where private care earns its keep.
We’re careful about what a private pathway for allergy blood tests can and can’t promise. It can compress a wait, put you in front of a subspecialist quickly, and get a proper report in your hands within a week. It can’t rewrite what the imaging or the bloods say. Setting that expectation up front tends to make the whole experience less stressful.