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Anaphylaxis: Identifying Triggers

An awareness guide to anaphylaxis triggers and the role of nurse-led, component-resolved IgE blood testing

🚨 Anaphylaxis is a medical emergency — call 999 immediately

If you or someone you are with shows signs of anaphylaxis — difficulty breathing, swelling of the lips, tongue or throat, wheeze, persistent cough, dizziness, collapse, or a sudden drop in blood pressure — call 999, ask for an ambulance, and say "anaphylaxis".

If an adrenaline auto-injector (such as EpiPen, Jext or Emerade) has been prescribed, use it without delay following the instructions provided with the device, then call 999. Lie the person flat with their legs raised (or sit upright if breathing is difficult). A second dose may be needed if symptoms do not improve within 5 minutes and another auto-injector is available.

For urgent but non-emergency advice, call NHS 111. For up-to-date first-aid guidance refer to Resuscitation Council UK guidelines or Anaphylaxis UK.

What Is Anaphylaxis?

Anaphylaxis is a severe, rapidly developing systemic allergic reaction that affects multiple body systems at once. It is typically triggered by exposure to a substance the immune system has previously become sensitised to, resulting in the rapid release of mast-cell mediators such as histamine and tryptase. According to NICE and the Resuscitation Council UK, anaphylaxis is a clinical diagnosis based on the abrupt onset and pattern of symptoms — it is not made on the basis of any single blood marker.

UK hospital admissions for anaphylaxis have risen steadily over the past two decades. Although fatalities remain rare, anaphylaxis can be life-threatening, particularly when adrenaline is delayed. Awareness of triggers, early recognition, and timely adrenaline are the cornerstones of safer outcomes.

Blood-based allergy testing has a specific, supportive role in this picture: it can help identify which allergens an individual is sensitised to. This information is interpreted by a clinician — usually an allergy specialist — alongside the full clinical history of any past reactions. It is one piece of the puzzle, not a diagnosis in itself.

Common Anaphylaxis Triggers

The pattern of triggers varies with age. In children, food is the most common cause; in adults, drugs and insect stings become more prominent. The categories below are the most frequently reported in UK clinical practice.

1. Foods

The leading paediatric triggers in the UK include peanut, tree nuts, cow's milk, egg, shellfish, fish, sesame, and wheat. Adult-onset food triggers also include alpha-gal (delayed reactions to red meat following a tick bite). Component-resolved diagnostics such as the peanut components panel and the broader nuts & seeds profile can clarify whether sensitisation is to a high-risk storage protein or a cross-reactive component.

2. Insect venom

Stings from bees and wasps are a common adult trigger in the UK. Severe reactions warrant referral to an allergy specialist for assessment, who may consider venom immunotherapy. The insect venom allergy profile measures specific IgE to bee, wasp and related venoms. See also our insect sting allergy guide.

3. Medications

Antibiotics (particularly penicillins and cephalosporins), non-steroidal anti-inflammatories (NSAIDs), neuromuscular blocking agents used in anaesthesia, and certain contrast media are the most frequently implicated drug triggers. Drug allergy assessment is led by NHS allergy clinics; blood testing is one component of that pathway and may be requested by your specialist. Our drug allergy page covers this further.

4. Latex

Natural rubber latex remains a recognised trigger, particularly in healthcare workers and patients with frequent surgical exposure. Specific IgE testing via the latex components test can help characterise sensitisation. See latex allergy for more.

5. Exercise- and co-factor-induced

Wheat-dependent exercise-induced anaphylaxis (WDEIA), driven by sensitisation to omega-5-gliadin, is one example where reactions occur only when a food is combined with exercise, alcohol or NSAIDs. The wheat components test includes omega-5-gliadin and can support specialist investigation.

6. Idiopathic anaphylaxis

In a proportion of cases, no trigger is identified despite thorough investigation. Such cases require specialist allergy assessment. Related conditions to consider include mastocytosis and angioedema.

How Blood Testing Fits Into Anaphylaxis Care

Blood-based specific IgE testing has a well-defined supporting role. Importantly:

→ IgE testing identifies sensitisation — whether your immune system has produced antibodies to a particular allergen. It does not predict the severity of any future reaction.
→ Component-resolved diagnostics (CRD) such as ALEX² break allergens down into their individual proteins, helping to distinguish high-risk components from cross- reactive ones. For example, sensitisation to peanut storage protein Ara h 2 is more strongly associated with severe reactions than sensitisation to the cross-reactive birch-related Ara h 8.
→ Baseline serum tryptase measured during a symptom-free period can provide useful background context when interpreted by a specialist; acute tryptase taken in hospital during an event has a separate role in confirming mast cell activation.
→ Results do not replace a clinical assessment, an emergency action plan or a prescribed adrenaline auto-injector. Testing is a complement to specialist care, not a substitute for it.

If you have a history of anaphylaxis or suspected severe allergy, the safest pathway is GP → NHS allergy specialist. Private blood testing through our clinic can be a useful intermediate step to clarify sensitisation patterns to discuss at that appointment.

How Testing Works

Choose Your Test

Select from our range of allergy blood tests and book a convenient time at our South Kensington clinic. No GP referral needed.

Nurse Blood Draw

A qualified nurse takes a small blood sample at our clinic. The appointment is quick and straightforward.

Get Your Results

Results are sent directly to you, typically within a few working days. Share them with your GP or specialist to guide your next steps.

ALEX² Multi-Allergen Component Test

Where the trigger of a past reaction is uncertain, the ALEX² multiplex panel measures specific IgE against around 300 allergen extracts and individual components from a single blood sample — including high-priority components for anaphylaxis assessment such as Ara h 2 (peanut), Cor a 14 (hazelnut), omega-5- gliadin (wheat) and Pru p 3 (peach lipid transfer protein). Sample collection is carried out at our nurse-led South Kensington clinic; results are released to you to share with your GP or allergy specialist for interpretation.

View the ALEX² Test →

Includes detail on, for example:

· Ara h 2 (peanut)
· Cor a 14 (hazelnut)
· Omega-5-gliadin (wheat)
· Pru p 3 (stone fruit LTP)
· Bet v 1 (birch / PR-10)
· Tropomyosins (shellfish)

Other Tests That May Be Relevant

Why Nurse-Led Sample Collection Matters

When the question being investigated is potentially anaphylactic in nature, the reliability of the sample matters. Multiplex assays such as ALEX² depend on correct tube selection, accurate labelling, gentle handling and timely processing. All blood samples at AllergyClinic.co.uk are taken by registered nurses experienced in allergy-pathway phlebotomy. We are CQC-registered and operate strictly within a diagnostic-only scope.

In practical terms, that means: we do not diagnose anaphylaxis, prescribe medication, issue or alter emergency action plans, or interpret your results into a clinical decision. Those steps sit with your GP or allergy specialist. Our role is to deliver a high-quality sample, return a clearly formatted laboratory report, and release that report to you for onward sharing.

Why Choose a Diagnostic-Only Clinic?

Unlike clinics that provide both testing and treatment, our nurse-led service focuses solely on accurate diagnostic testing. Because we don't offer treatments or prescriptions, there is no commercial incentive to recommend unnecessary tests — just honest, impartial results you can trust.

Nurse-Led & Impartial

Our qualified nurses collect your sample — we don't prescribe, treat, or have any reason to upsell.

Results You Own

Your results are sent directly to you. Take them to your GP or a specialist to discuss what's best for your situation.

You Stay in Control

Understand your allergy profile, then decide with your healthcare professional what steps to take next.

Related Conditions

Frequently Asked Questions

What is anaphylaxis?

Anaphylaxis is a severe, potentially life-threatening allergic reaction that develops rapidly — typically within minutes of exposure to a trigger. It involves multiple body systems and most commonly affects breathing (wheeze, throat tightness), circulation (dizziness, collapse, drop in blood pressure), and the skin (widespread hives, swelling). Anaphylaxis is a medical emergency that requires immediate treatment with adrenaline and a 999 call.

Can a blood test diagnose anaphylaxis?

No. Anaphylaxis is a clinical diagnosis made by a doctor based on the pattern and severity of symptoms, not a laboratory test. Specific IgE blood testing identifies whether you are sensitised to particular allergens, which can support the investigation of past reactions and identification of triggers — but it does not predict whether, when or how severely an individual will react.

How can the ALEX² test help if I have had anaphylaxis?

ALEX² is a component-resolved multiplex test that measures specific IgE against around 300 allergen extracts and individual allergen components from a single blood sample. For people with a history of anaphylaxis where the trigger is uncertain, it can help clarify sensitisation patterns, including high-risk components such as Ara h 2 (peanut), Cor a 14 (hazelnut), omega-5-gliadin (wheat-dependent exercise-induced anaphylaxis) and Pru p 3 (peach lipid transfer protein). Results should always be interpreted by an allergy specialist alongside your clinical history.

Does a positive test mean I will have anaphylaxis?

No. Sensitisation (a positive specific IgE) does not equate to clinical allergy or predict the severity of a reaction. Many people with positive IgE results experience either mild symptoms or no symptoms at all. Only a clinician — usually an allergy specialist — can interpret results in the context of your full clinical picture.

I have been told to carry an adrenaline auto-injector. Should I still get tested?

Allergy testing can be a useful step where the trigger of a previous reaction is unclear, or where avoidance advice could be refined. Discuss with your GP or allergy specialist before booking. Testing complements — but does not replace — specialist management, an emergency action plan, and carrying your prescribed adrenaline auto-injector (such as EpiPen, Jext or Emerade) at all times.

Why does our nurse-led service matter for this kind of testing?

All blood samples at our CQC-registered clinic are taken by qualified nurses experienced in phlebotomy and allergy testing pathways. Sample quality, correct tube selection and accurate labelling matter for the reliability of multiplex assays such as ALEX². Our role is strictly diagnostic — we do not diagnose, treat or manage anaphylaxis; your results are released to you to share with your GP or allergy specialist.

Investigate Sensitisation — Not a Substitute for Specialist Care

If you have ever had a severe allergic reaction, please ensure you are under the care of your GP or an allergy specialist and that any prescribed adrenaline auto-injector is carried at all times. Our nurse-led blood testing service is one supportive step in that wider pathway.

View the ALEX² Multi-Allergen Test →