Specific IgE blood tests (Allergen-specific immunoglobulin E (sIgE) blood testing)

What is a specific IgE blood test?

A specific IgE blood test measures the amount of a particular allergy antibody (immunoglobulin E, or IgE) in your blood against a chosen allergen — for example peanut, cat, grass pollen or house dust mite. It is sometimes still called a RAST test, though modern versions use different technology.

It is useful when there is a clear story of an immediate allergic-type reaction, and it has a practical advantage over skin testing: it is not affected by antihistamines, so you do not need to stop them, and it can be used when skin testing is difficult. A single blood draw can test for several allergens.

The crucial point is interpretation. A positive result shows sensitisation — that your immune system has made antibodies — not that you are definitely allergic. Many people test positive to foods or other allergens they tolerate perfectly well. The level of IgE does not reliably predict how severe a reaction would be. The test only means something when read alongside your symptoms, which is why it should not be used to screen blindly for allergy.

Types, options & approaches

There may be different ways to do this. The right approach depends on the clinical question and your circumstances.

Specific IgE blood test versus skin prick test

Neither test diagnoses allergy on its own. Both detect sensitisation and must be read alongside your history; they are often complementary rather than competing.

Preparing for your test

• Have a clear account of your symptoms and suspected triggers, as this guides which allergens are worth testing.
• You do not need to stop antihistamines for this test, unlike skin testing.
• Continue your usual medicines unless told otherwise.
• Bring details of any previous allergy tests or reactions.
• If you are anxious about blood tests, let the staff know.
• For children, plan for a blood sample and bring distraction or comfort items.

What happens

A small blood sample is taken from a vein, usually in the arm, in the same way as any routine blood test. It is sent to a laboratory, which measures the level of IgE antibody to each requested allergen.

There is no waiting around for a skin reaction and no reaction risk from the test itself. Results come back over days to a couple of weeks. A clinician then interprets each result alongside your symptoms — a positive result that fits your history is far more meaningful than one that does not.

You should be told what each result means for you, what to avoid (and what not to avoid unnecessarily), and whether any further testing, such as a supervised challenge, would help clarify things.

Is this test right for me?

A good consultation should explore whether it's the right choice for you now — including reasons to wait or consider something else.

Before you decide

Use this as a shared-decision checklist. The aim is not just “can this be done?”, but whether it is right for you, now, with the risks and alternatives clearly understood.

The real risk with this test is not the blood draw but over-interpretation. A positive result only shows sensitisation, and the IgE level does not reliably predict how severe a reaction would be. False positives are common, partly from cross-reactivity. Always ask the clinician what a result means for you specifically, and never start strict avoidance of an important food on the basis of a blood test alone.

Published figures to discuss

Specific IgE testing detects sensitisation, which is far more common than true allergy, so positive results do not equal allergy and the level does not reliably predict reaction severity. False positives occur, partly from cross-reactivity between related proteins and cross-reactive carbohydrate determinants. Diagnostic accuracy varies widely by allergen, age and the cut-off used, which is why exact percentages are not given here and results must be read with the clinical history.

These are literature figures, not a personalised prediction. Your own risks and likely benefits depend on your circumstances, your health, and how your care is carried out and followed up.

What happens afterwards

There is no physical recovery. Afterwards, what matters is understanding what each result means alongside your symptoms, and not over-restricting your diet or activities on the basis of a positive test alone.

• Slight bruising or tenderness at the needle site for a day or two.
• Waiting days to a couple of weeks for results.
• Finding that some positive results do not match your symptoms.
• Needing the results explained rather than reading them yourself.
• Being asked for a further test if the answer is not clear-cut.

Aftercare

• Wait for a clinician to interpret the results with you before changing your diet or routine.
• Do not cut out important foods on the basis of a positive result alone.
• Follow any avoidance or emergency advice you are given.
• Keep using any prescribed allergy treatments as directed.
• Ask about a supervised challenge if you and the clinician are unsure.
• Make sure your GP has the results and any plan.
• Seek urgent help for any severe reaction while awaiting results.

• A clear account of your symptoms and suspected triggers
• Details of previous allergy tests or reactions
• List of your current medicines
• Questions about what a positive or negative result will change
• Comfort items for a child having blood taken
• Your GP's details so results can be shared
• A note not to start avoidance until results are explained

⚠ Get urgent help if…

• These warning signs relate to an allergic reaction, not the blood test itself.
• Difficulty breathing, wheeze, or a tight or swollen throat after a suspected trigger.
• Swelling of the lips, tongue or face.
• Feeling faint, dizzy or collapsing during a reaction.
• A widespread rash or hives with any breathing or swallowing difficulty.
• Any reaction worse or faster than before — use an adrenaline auto-injector if prescribed and call 999.

Who to contact: your clinician, clinic or test provider first (keep their number to hand). For urgent advice when you can't reach them, call NHS 111. In an emergency, call 999.

General guidance — it doesn't replace the specific advice your specialist gives you.

Results & realistic expectations

A positive result that fits your symptoms supports an allergy and helps guide avoidance and treatment. A negative result makes an immediate (IgE-mediated) allergy less likely, though it does not rule out every kind of reaction. The most useful results are those that match your history.

The test cannot prove allergy on its own, cannot reliably predict how severe a future reaction would be, and frequently shows sensitisation to things you tolerate. A confident diagnosis sometimes needs further tests or a supervised challenge.

IgE levels can change over time. In children, levels to some foods may fall as an allergy is outgrown, while new sensitisations can appear at any age. Repeat testing is sometimes used to follow these changes, but timing and interpretation should be guided by a clinician rather than tested repeatedly without reason.

Related tests, treatments or support

Specific IgE testing is often used alongside skin prick testing, and may be followed by component-resolved diagnostics for a more detailed picture or a supervised oral food challenge to confirm a diagnosis. It is interpreted as one part of the overall allergy assessment.

Follow-up & long-term care

Follow-up depends on the results. A clear result matching your history may complete the assessment, with a letter to your GP. Unclear or mismatched results may lead to component testing or a supervised challenge, then review to confirm the diagnosis and agree management.

• Repeat testing only when there is a clinical reason, such as checking whether a child is outgrowing an allergy.
• Reviewing results if symptoms or circumstances change.
• Keeping confirmed allergies recorded with your GP and pharmacy.
• Reassessing any emergency plan as the situation changes.

Repeat, follow-on and what comes next

• Unclear or mismatched results often need component testing or a supervised challenge to resolve.
• Levels can change over time, so testing may be repeated when there is a clinical reason.
• A positive result you tolerate may need confirming with a challenge before any avoidance.

Ask what happens if the result is unclear or needs repeating, and what is included if further tests or follow-up are needed.

What good aftercare looks like

• Clear interpretation of each result against your symptoms, not just a printout.
• Sensible avoidance advice, and reassurance where avoidance is not needed.
• An emergency plan and auto-injector where a significant allergy is confirmed.
• Results and plan shared with your GP.
• A clear route to further testing, such as a challenge, if needed.

What affects the cost

Costs vary a great deal between people and providers, and we don't publish prices. What matters is understanding what drives the cost and making sure your quote is complete. The main things that affect it:

• How many allergens are tested.
• Whether more detailed component tests are added.
• The laboratory used and turnaround time.
• Whether a clinician consultation to interpret the results is included.
• Whether further testing, such as a supervised challenge, follows.
• Whether the test is part of a wider allergy assessment.

• The cost per allergen or per panel.
• Whether a consultation to interpret the results is included.
• Who reports and explains the results.
• Whether a letter to your GP is provided.
• What further tests might be needed and roughly what they involve.
• What happens if the result does not match your symptoms.
• The cancellation policy.

On the NHS? Specific IgE blood testing is available on the NHS when clinically indicated and often requested by a GP or specialist; private testing is widely offered but should still be targeted and interpreted alongside your symptoms.

You're entitled to your total cost in writing — including reports, follow-up and what happens if the result is inconclusive — before you decide.

Consent traps and marketing red flags

These are not small details. They are often where patients lose choice, time to reflect, or realistic expectations.

Choosing a specialist safely

• Check the specialist is on the GMC Specialist Register for this area.
• Make sure they work at a CQC-registered service, and look for membership of the relevant Royal College or professional body.
• You're entitled to time to consider and to have your questions answered before you agree — the specialist who looks after you should explain it, not a salesperson.
• Be wary of pressure: time-limited offers or deposits taken before you've had time to think are red flags, not bargains.
• You're entitled to your total cost in writing — including any follow-up — before you decide.

How Vuemedics verifies every consultant →

Take this to your consultation. A good specialist will welcome every one of these.

• Which allergens are you testing, and why these based on my history?
• What will a positive or negative result actually change for me?
• Could a positive result simply mean sensitisation to something I tolerate?
• Would a more detailed component test or a supervised challenge help clarify things?
• What should I avoid, and what should I not avoid unnecessarily?
• How will the results be explained to me and shared with my GP?
• Are you on the GMC Specialist Register for this area, and which Royal College or professional body are you a member of?
• Will you be the specialist who carries out my test, and who looks after me afterwards?
• What are the risks for someone like me, and how often do your own patients have a problem or need it repeated or redone?
• What does a realistic result look like — and what can this test not achieve?
• What are my options, including waiting, doing nothing for now, or choosing a different approach?
• Can I have written information, results and aftercare instructions in a format I can use, including any accessibility or communication support I need?
• What is the total cost in writing, including any follow-ups, and how much time do I have to decide?

Find a verified specialist for specific ige blood tests

Every consultant is GMC-checked and independently reviewed. Search by postcode and distance, or switch to a map. Ordered by rating, relevance and recency — never by who pays.

How we made this page

Medically reviewed by a GMC-registered consultant. Written in plain English, checked against NHS, NICE, GMC and relevant Royal College / specialist-society guidance, and kept under review. No clinic paid to appear on this page, and we publish no pricing. This is general information to help you prepare — it is not a substitute for advice from your own clinician. How we review our guides →

Source hierarchy: UK regulator and NHS/NICE guidance first, then relevant Royal College or specialist-society guidance, then peer-reviewed evidence for procedure-specific figures where available.

Sources & standards: Allergy UK — Food allergy testing and diagnosing Anaphylaxis UK — Allergy testing NHS — Allergies: diagnosis ASCIA — Laboratory tests in the diagnosis of allergic diseases BSACI guidelines for the management of allergic and non-allergic rhinitis (PMC)

Reviews reflect patients' experience of care, not clinical outcomes. For procedure volumes and outcome data see PHIN.

Last medically reviewed 2026-09-21. Spotted something wrong or out of date? Report an error in this guide.