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Accurate allergy diagnosis depends on far more than a single blood test. At the London Allergy and Immunology Centre, our consultants deploy a structured, guideline-aligned diagnostic pathway tailored to each patient’s clinical picture — combining skin tests, molecular blood analysis, functional assays, and supervised challenges where needed. We offer over 600 validated allergy tests, interpreted in clinical context by experienced GMC-registered specialists.
Our diagnostic approach is aligned with the EAACI 2025 guidelines on the diagnosis and management of IgE-mediated food allergy, which confirm that component-resolved diagnostics (CRD) should be used to distinguish genuine sensitisation from cross-reactive responses, and that the Basophil Activation Test (BAT) is now — for the first time — listed as a recommended test in clinical practice for selected patients with equivocal results prior to oral food challenge.
Why Specialist Allergy Testing Matters
The Problem with Basic Testing
A positive IgE blood test for peanut does not confirm peanut allergy — 11.8% of UK school-aged children test positive, yet only 2.6% are genuinely allergic when formally challenged. Conversely, standard tests can miss clinically significant reactions. Misdiagnosis in either direction has serious consequences.
The Value of Precise Diagnosis
Specialist testing identifies which specific proteins are responsible for a reaction, distinguishes allergy from tolerance and from birch pollen cross-reactivity, establishes risk level and severity markers, determines immunotherapy candidacy, and avoids unnecessary dietary restrictions that impair quality of life.
Our Approach
We investigate symptoms carefully rather than relying on broad screening alone. Each diagnostic pathway is selected by a consultant based on clinical history, symptom pattern, and prior test results. We follow EAACI, BSACI, and NICE evidence-based guidelines throughout.
Important: All allergy tests must be interpreted by a specialist in the context of a full clinical history. A positive test result alone — without clinical correlation — is not a diagnosis. Our consultants provide this clinical interpretation at every step.
Our Consultant-Led Diagnostic Pathway
Every patient follows a structured, stepwise diagnostic pathway based on EAACI 2025 recommendations:
Detailed Clinical History
Thorough history of symptoms, timing, severity, triggers, co-existing conditions (atopic dermatitis, asthma, rhinitis), family history, and medications. This is the single most important diagnostic step and guides test selection.
First-Line Tests: SPT and/or Specific IgE
Per EAACI 2025, skin prick tests (SPT) and specific IgE blood tests to allergen extracts are first-line investigations — high sensitivity but moderate specificity. Results interpreted alongside clinical history to classify sensitisation as likely clinically relevant or likely cross-reactive/incidental.
Component-Resolved Diagnostics (CRD): ALEX³ / ISAC
Molecular profiling of specific allergen components (e.g. Ara h 2 for peanut, Bet v 1 for birch, Der p 1 for dust mite). High specificity. Identifies genuine primary sensitisation vs cross-reactive low-risk proteins. Guides immunotherapy selection and risk stratification. Now standard in our diagnostic pathway.
Basophil Activation Test (BAT) — New in EAACI 2025 Guidelines
For the first time included in EAACI food allergy diagnostic guidelines (2025). Recommended for patients with equivocal SPT and IgE results prior to oral food challenge. Particularly evidenced for peanut and sesame. Reduces the need for diagnostic food challenges and adds functional diagnostic certainty.
Oral Food Challenge / Drug Provocation Test
Gold standard for confirming or excluding allergy when clinical history and blood/skin tests are inconclusive, or for establishing a reaction threshold. Conducted in clinic with full resuscitation facilities. Also used for de-labelling unnecessary allergy diagnoses.
Skin Prick Testing (SPT)
Skin prick testing is one of the most widely used and well-validated first-line allergy diagnostic methods. A small drop of standardised allergen extract is placed on the forearm and a lancet creates a tiny puncture through the droplet. A positive response — a wheal-and-flare reaction — appears within 15–20 minutes if IgE-mediated sensitisation is present.
SPT is safe from birth when clinically appropriate and is a mainstay of paediatric allergy investigation. It is used for food allergens, inhalant allergens (pollens, dust mite, pet dander, moulds), insect venoms, drugs (penicillin, latex), and occupational allergens.
Important preparation: Antihistamines must be stopped for a minimum of 3–7 days before testing (depending on the antihistamine). Your consultant will advise. Do not stop asthma inhalers.
At a Glance
Results: 15–20 minutes
Suitable from: Birth (when clinically appropriate)
Preparation: Stop antihistamines 3–7 days before
Used for: Foods, pollens, pets, dust mite, mould, venom, drugs, latex
Sensitivity: High (first-line)
Specific IgE Blood Tests (RAST / ImmunoCAP)
Specific IgE blood tests measure the level of IgE antibodies produced by the immune system in response to individual allergens. We use the ImmunoCAP platform — the international reference standard — to test for specific IgE against over 600 allergen extracts and components.
Blood tests are particularly useful when skin testing is not possible or appropriate — for example in patients with severe eczema or dermatographism, those who cannot stop antihistamines, infants requiring a small blood volume, or patients with a high risk of systemic reaction to skin testing.
Interpretation note: A positive specific IgE result indicates sensitisation, not necessarily clinical allergy. The clinical significance of any positive result must be evaluated by a specialist in conjunction with the patient’s clinical history.
At a Glance
Results: 3–7 days
Platform: ImmunoCAP (international reference standard)
No preparation needed: Antihistamines need not be stopped
Suitable for: All ages, including babies
Covers: 600+ allergens
ALEX³ & ISAC Molecular Allergy Testing (Component-Resolved Diagnostics)
Component-resolved diagnostics (CRD) are now recommended as standard in the EAACI 2025 IgE-mediated food allergy diagnostic guidelines to distinguish primary sensitisation from cross-reactive responses and to guide immunotherapy candidate selection. CRD identifies the specific molecular proteins (allergen components) responsible for sensitisation — information that determines true clinical risk.
ALEX³ Allergy Xplorer
300+ Allergen Components — Single Blood Sample
The ALEX³ platform simultaneously tests over 300 allergen components — including species-specific proteins, cross-reactive molecules, and molecular risk markers — from a single blood sample. It is the broadest component panel available in clinical practice and has been updated in 2025 to include new allergen components.
What it tells you:
- Which specific proteins within a food or inhalant allergen are causing sensitisation
- Whether sensitisation represents true primary allergy (e.g. Ara h 2 in peanut) or cross-reactive low-risk sensitisation (e.g. Ara h 8 linked to birch pollen)
- Which patients are at highest risk of severe reactions vs likely to tolerate the food
- Which inhalant allergens are primary sensitisers vs cross-reactive — critical for choosing the correct immunotherapy
Available as: In-clinic blood draw (London) or UK-wide postal home kit
ISAC (ImmunoCAP ISAC)
112 Components — Biochip Multiplex Platform
The ISAC biochip simultaneously measures specific IgE to 112 allergen components using just a few microlitres of blood or serum. Particularly valuable for polysensitised patients with multiple allergies and complex symptom patterns, and for distinguishing cross-reactive carbohydrate determinants (CCDs) from genuine sensitisation.
Particularly useful for:
- Patients sensitised to many allergens simultaneously
- Clarifying which sensitisations are clinically relevant
- Identifying CCD cross-reactivity that inflates conventional IgE panels
- Pre-immunotherapy selection and monitoring
| Allergen | High-Risk Component (genuine allergy) | Low-Risk Component (cross-reactive) | Clinical Implication |
|---|---|---|---|
| Peanut | Ara h 2, Ara h 6 (2S albumins) | Ara h 8 (PR-10, birch cross-reactive) | Ara h 8 alone → oral allergy syndrome, not anaphylaxis |
| Birch pollen / hay fever | Bet v 1 (PR-10) | Profilin (Bet v 2) | Bet v 1 sensitisation guides SLIT/SCIT immunotherapy selection |
| House dust mite | Der p 1, Der p 2 (major mite allergens) | Cross-reactive tropomyosin | Der p 1/2 positivity supports HDM immunotherapy candidacy |
| Wasp / Bee venom | Api m 1 (bee), Ves v 5 (wasp) | Cross-reactive carbohydrate determinants (CCDs) | CRD essential to select correct venom immunotherapy |
Basophil Activation Test (BAT) — 2025 EAACI Recommended
New in 2025: The Basophil Activation Test (BAT) is now, for the first time, listed as a recommended test in the EAACI guidelines on the diagnosis of IgE-mediated food allergy. It is suggested for patients with a suspected food allergy and equivocal skin prick and specific IgE results, prior to oral food challenge — particularly for peanut and sesame allergy.
The BAT is a functional ex vivo assay that measures the activation of basophils (allergy effector cells) in response to allergen exposure. Unlike IgE tests, it assesses how the patient’s immune cells actually respond to the allergen — providing a closer functional correlate to clinical reactivity.
How It Works
Fresh blood is incubated with the allergen. Basophil activation markers (CD63, CD203c) are measured by flow cytometry. A dose-dependent upregulation indicates IgE-mediated sensitisation with functional relevance.
Diagnostic Performance
For peanut, BAT achieves 97% accuracy, 95% positive predictive value, and 98% negative predictive value. It can reduce the number of required oral food challenges by up to two-thirds, making it a valuable and safer alternative for selected patients.
When BAT is Used
Equivocal peanut or sesame allergy (mid-range IgE); patients unsuitable for food challenge; monitoring tolerance induction during OIT; drug and venom allergy assessment where conventional tests are inconclusive. Requires fresh blood processing by trained laboratory staff.
Limitations
Requires fresh blood processed within hours of collection. Approximately 5–10% of patients are “non-releasers” whose basophils do not respond. Requires specialist flow cytometry equipment and EAACI-standardised protocols. Not suitable as a routine first-line screening test.
Oral Food Challenge Tests (OFC)
The double-blind placebo-controlled food challenge (DBPCFC) remains the gold standard for confirming or excluding food allergy. An oral food challenge involves the supervised administration of increasing doses of the suspect food in a controlled clinical environment with immediate access to resuscitation facilities.
When an OFC is Used
- Confirming or excluding food allergy when history and blood/skin tests are inconclusive
- Establishing a reaction threshold for immunotherapy dosing
- Assessing whether a child has grown out of a food allergy
- De-labelling an unconfirmed allergy diagnosis
Safety Record
A large multicentre prevalence study found that 86% of open low-risk challenges resulted in no reaction at all, and 98% were completed without anaphylaxis. All challenges are performed by trained allergy specialists with immediate resuscitation available on site.
Types of Challenge
- Open OFC: both patient and clinician know the food — suitable for most clinical use
- Single-blind OFC: patient unaware, clinician aware
- DBPCFC: neither patient nor clinician aware — research and disputed diagnoses
Drug Allergy Testing & De-labelling
Up to 10% of the UK population reports a “penicillin allergy” label, yet studies show that over 90% of these patients are not genuinely allergic when formally assessed. An incorrect drug allergy label leads to use of broader-spectrum antibiotics, increased antimicrobial resistance, worse clinical outcomes, and higher healthcare costs. Our consultants offer a comprehensive drug allergy assessment and de-labelling service.
Penicillin & Beta-Lactam Allergy
Skin testing to major and minor penicillin determinants, followed by supervised graded challenge where appropriate. Formal de-labelling letter provided for your GP and medical records.
NSAID / Aspirin Hypersensitivity
Assessment of NSAID-exacerbated respiratory disease, NSAID-induced urticaria/angioedema, and single NSAID hypersensitivity. Supervised aspirin challenge with spirometry where indicated.
Anaesthetic & Perioperative Allergy
Specialist investigation of suspected reactions to anaesthetic agents, muscle relaxants, antibiotics, and latex during surgical procedures. Assessment prior to planned surgery in high-risk patients.
Vaccine Allergy Assessment
Assessment of suspected reactions to vaccines — including MMR, influenza, COVID-19 vaccines. Graded challenge protocol available in clinic for patients requiring vaccination who have reported prior reactions.
Patch Testing for Contact Dermatitis
Patch testing is the gold standard investigation for allergic contact dermatitis (ACD) — a delayed Type IV (T-cell mediated) hypersensitivity reaction to chemical substances in contact with the skin. It is distinct from IgE-mediated allergy and requires a completely different diagnostic approach.
Panels of common contact allergens (European Standard Series, cosmetics, metals, rubber, and occupation-specific series) are applied in small aluminium chambers to the upper back and left in place for 48 hours. Readings are taken at 48 hours and again at 72–96 hours. Results are interpreted by our dermatology consultants in the context of exposure history.
Common patch test allergens: nickel, fragrances, preservatives (methylisothiazolinone, formaldehyde releasers), hair dye (PPD), rubber accelerators, topical medicaments, and occupational chemicals. Our dermatology consultants provide full occupational and cosmetic allergy assessments.
Other Specialist Tests We Offer
Urticaria Histamine Release Test
Measures histamine released from basophils in response to patient serum — used in the investigation of autoimmune chronic spontaneous urticaria (CSU) and for guiding omalizumab therapy decisions.
Baseline Serum Tryptase
Elevated baseline tryptase indicates mast cell burden and is the principal screening test for mastocytosis. Essential for risk stratification in venom allergy and in patients with severe or recurrent unexplained anaphylaxis.
Intradermal Testing
Higher sensitivity than SPT for drug allergy (penicillin, anaesthetics) and venom allergy when SPT is negative but clinical suspicion remains high. Performed by trained consultants with emergency facilities available.
Spirometry & Lung Function
Specialist lung function testing to diagnose and characterise allergic and non-allergic asthma in adults and children. Includes reversibility testing, fractional exhaled nitric oxide (FeNO) for eosinophilic airway inflammation, and exercise challenge where indicated.
Gluten & Lactose Intolerance
Coeliac serology (IgA tTG antibody, IgA EMA), HLA-DQ2/DQ8 genotyping, hydrogen breath test for lactose intolerance. Referral for small bowel biopsy when clinically indicated. Distinction from IgE-mediated wheat allergy provided.
Immunology Screening
Immunoglobulin levels (IgG, IgA, IgM, IgE subclasses), complement levels, lymphocyte subsets, specific antibody responses to vaccines — for investigation of recurrent infections and suspected primary immunodeficiency.
At-Home Allergy Testing — UK-Wide Postal Testing
Our ALEX³ at-home postal testing service allows patients anywhere in England, Scotland, Wales, and Northern Ireland to access the same advanced molecular allergy diagnostics available at our London clinics — without needing to travel.
How it Works
- Purchase the ALEX³ test online
- Home blood sample collection kit sent to your address
- Return sample to laboratory by post
- Results available in secure online health record (Carebit) within days
- Consultant review and video consultation to discuss findings
Important Notes
- Finger-prick testing may not be suitable for babies or very young children — a trained professional sample may be needed
- Results are always reviewed and interpreted by a consultant, not by algorithm alone
- If further testing or treatment is required, a clinic appointment is arranged
- International samples accepted — discuss logistics before purchase
Tests We Do Not Offer — and Why
The UK private health sector contains many unvalidated allergy tests marketed directly to the public. These tests are not recommended by EAACI, BSACI, or NICE, produce unreliable results, and can lead to unnecessary dietary restrictions, nutritional deficiencies, anxiety, and delayed diagnosis of genuine allergy.
| Test Name | Marketed Claim | Evidence Status |
|---|---|---|
| IgG food intolerance panels | Identifies “food intolerances” | IgG to foods is a normal response to eating those foods; not diagnostic of allergy or intolerance. Condemned by EAACI, BSACI, NICE. |
| Hair mineral analysis | Detects “food sensitivities” | No validated diagnostic mechanism. No evidence of clinical utility. |
| Vega / electrodermal testing | Allergy detection via electrical current | No scientific basis. Results no better than chance in controlled studies. |
| Applied kinesiology | Muscle strength testing for allergy | Not scientifically validated. No evidence of reliability or clinical value. |
| Cytotoxic (ALCAT) testing | Cell reaction “food sensitivity” testing | Not recommended. Poor reproducibility and no correlation with clinical allergy. |
If you have received results from any of these tests and are following a restricted diet on their basis, we strongly recommend a specialist consultation to review your actual allergy status. Unnecessary avoidance of foods — particularly in children — can cause nutritional deficiencies and may delay the natural development of tolerance.
Important Notice
All allergy tests must be interpreted by a specialist in the context of a full clinical history. A positive test result alone is not a diagnosis of allergy. This page provides general educational information only. In a medical emergency, call 999.
References
- Santos AF, Riggioni C, et al. EAACI Guidelines on the Management of IgE-mediated Food Allergy. Allergy. 2025;80(1):1–28. doi:10.1111/all.16345
- Pascal M, Chauhan J, et al. Basophil Activation Test: Bridging Allergy and Oncology — EAACI Position Paper. Allergy. 2025;80:2097–2112. doi:10.1111/all.16607
- Arasi S, Niegowska MA, et al. Basophil activation test (BAT): Clinical and research relevance in allergy diagnostics. Italian Journal of Pediatric Allergy and Immunology. 2026;40(1):36–43.
- Bergmann MM, Santos AF. Basophil activation test in the food allergy clinic: its current use and future applications. Expert Rev Clin Immunol. 2024;20:1297–1304.
- Hemmings O, Du Toit G, Radulovic S, Lack G, Santos AF. Ara h 2 is the dominant peanut allergen despite similarities with Ara h 6. J Allergy Clin Immunol. 2020;146(3):621–631.
- European Medicines Agency. Guideline on Allergen Products. EMA/16166/2026. January 2026.
- National Institute for Health and Care Excellence (NICE). Anaphylaxis: Assessment and Referral after Emergency Treatment. CG134. 2011 (reviewed 2020).
- BSACI Standards of Care for Allergy Services. British Society for Allergy and Clinical Immunology, 2022.
Page reviewed: June 2026 | London Allergy and Immunology Centre | privateallergy.uk