Intradermal allergy testing (Intradermal (intracutaneous) skin testing for allergy)
A test where tiny amounts of a suspected allergen are injected just under the skin to look for an allergic reaction, used mainly for drug and insect-venom allergy when skin prick testing is not enough.
✓ Medically reviewed by a GMC-registered consultant · last reviewed September 2026 · next review September 2027 · how we review
In short
- It injects a tiny amount of allergen just under the skin and is used mainly for drug and venom allergy, often when skin prick testing is negative.
- It is more sensitive but less specific than skin prick testing, so it finds more true allergies but also more results that do not mean real-world allergy.
- Because it carries a higher chance of a reaction, including the rare risk of a systemic reaction, it must be done in a specialist setting with emergency treatment available.
- A positive result shows sensitisation, not proof of allergy; it only makes sense interpreted alongside your history.
A plain-English summary. The detail — including risks and recovery — is below.
At a glance
A general guide. Your specialist will give you advice for your situation.
More sensitive than skin prick testing, so it can confirm allergy that prick testing misses.
It should never be used to 'screen' for allergy without a relevant clinical history.
Small injections just under the skin, then waiting about 15–20 minutes for the skin to be read and measured.
Clear interpretation of the result in light of your history, with realistic next steps.
Small injections just under the skin, then waiting about 15–20 minutes for the skin to be read and measured.
You are watched for a time in case of a wider reaction before going home.
The specialist explains immediate results, what they mean with your history, and what to avoid.
For some drug tests, the skin is rechecked for delayed reactions, and a plan is confirmed.
What is intradermal allergy testing?
Intradermal testing involves injecting a very small, diluted amount of a suspected allergen just beneath the surface of the skin, usually on the forearm, and watching for a raised, itchy bump (a wheal) over the next 15–20 minutes. It is more sensitive than skin prick testing, so it is mainly used for drug allergy (such as penicillin or anaesthetic drugs) and insect-venom allergy, often after skin prick tests are negative.
Because it places allergen below the skin surface, it carries a higher chance of a reaction than skin prick testing. For this reason it must be done by allergy specialists in a setting where reactions, including the rare risk of a whole-body (systemic) reaction, can be recognised and treated.
Intradermal testing can support a diagnosis, but it shows sensitisation rather than proving allergy. It is more sensitive but less specific than skin prick testing, meaning it picks up more true cases but also more results that do not reflect real-world allergy. The result must always be read alongside your clinical history, and it should never be used to 'screen' for allergy without one.
Types, options & approaches
There may be different ways to do this. The right approach depends on the clinical question and your circumstances.
Skin prick versus intradermal testing
| Feature | Skin prick test | Intradermal test |
|---|---|---|
| Method | Allergen pricked into surface | Allergen injected under skin |
| Sensitivity | Lower | Higher |
| Specificity | Higher | Lower |
| Reaction risk | Low | Higher |
| Main uses | Foods, pollens, animals | Drugs, venom (often after a negative prick test) |
The two tests are often used in sequence rather than as alternatives, with intradermal testing reserved for situations where it adds information.
Preparing for your test
- Stop antihistamines for the time the clinic advises (usually 3–5 days), as they can hide reactions; do not stop other regular medicines without advice.
- Tell the clinic about any heart or breathing conditions, pregnancy, or medicines such as beta-blockers, which can affect testing and the treatment of reactions.
- Bring a clear account of your original reaction — what drug or sting, how soon, how severe — and any hospital letters.
- Avoid testing if your skin is very inflamed (for example severe eczema) where it would be done, and tell the clinic.
- Allow time for the appointment, including an observation period after testing.
- Arrange to be able to get home, and ask whether you should avoid driving immediately afterwards.
- Do not stop any preventer asthma treatment; well-controlled asthma is important before testing.
What happens
Testing is done in a specialist clinic where staff can manage allergic reactions. After confirming your history and that it is safe to proceed, the clinician usually starts with skin prick testing, then moves to intradermal testing if needed.
For the intradermal part, a very small amount of diluted allergen is injected just under the skin, raising a tiny bleb. Often several dilutions or allergens are tested, alongside control injections. The skin is checked after about 15–20 minutes for a raised, itchy wheal, and the size is measured. Some drug tests are also read later for delayed reactions.
You are watched for a period afterwards in case of a wider reaction. The specialist interprets the results with your history and explains what they mean, what to avoid, and any next steps such as a supervised drug challenge.
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.
May not be suitable if…
- It should never be used to 'screen' for allergy without a relevant clinical history.
- It is not the right first test for most food allergy, where skin prick testing, specific IgE or a supervised challenge are more appropriate.
- It may be unsafe or unreliable in someone with severe, uncontrolled asthma, a very recent severe reaction, or extensive skin disease where it would be done.
- It is not a substitute for a supervised drug challenge when a definite answer about drug tolerance is needed.
Delay or rearrange if…
- You have a current infection, are acutely unwell, or have recently had a severe allergic reaction.
- You cannot safely stop antihistamines beforehand.
- Your asthma is poorly controlled.
- You are pregnant and the test could reasonably wait — discuss with the specialist.
- You are taking medicines such as beta-blockers that make reactions harder to treat, until this is reviewed.
Alternatives to discuss
- Skin prick testing alone where it gives enough information.
- Specific IgE blood tests, which carry no reaction risk to the patient.
- A supervised drug or food challenge as the definitive test where appropriate.
- Avoidance of the suspected drug with a documented alternative, where testing is not feasible.
- Venom-specific blood tests as part of venom allergy assessment.
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.
What matters most to me?
Think about symptoms, daily life, work, caring responsibilities, sport, fertility, travel, appearance and anxiety — the right choice depends on your priorities, not just the medical facts.
What are all my options?
Ask about waiting, monitoring, medicines, rehabilitation, a smaller or larger procedure, a different test, NHS referral, or a second opinion where that would help.
What would make me pause?
Active infection, pregnancy, unstable medical problems, smoking, medicines that increase bleeding, poor support at home, or feeling pressured are all reasons to slow down and get tailored advice.
What happens if I do nothing today?
For some problems, waiting is safe; for others, delay can make treatment harder. A good consultation should explain the trade-off in plain English.
Benefits
- More sensitive than skin prick testing, so it can confirm allergy that prick testing misses.
- Particularly useful for drug and insect-venom allergy where accurate diagnosis matters.
- Can help confirm which specific drug or venom is responsible.
- Helps guide treatment, such as choosing safe alternative medicines or venom immunotherapy.
- Done with controls and increasing strengths to improve safety and interpretation.
- Results are available the same day for immediate reactions.
Risks & complications
- Itching and a raised bump at the test sites, which settle over a few hours.
- Temporary redness or mild swelling where injections were given.
- Discomfort from several small injections.
- A larger local skin reaction that takes longer to settle.
- A positive result that does not reflect real-world allergy (false positive), as the test is less specific than skin prick testing.
- A negative result despite a genuine allergy, so the history still guides decisions.
- Needing further tests, such as a supervised drug challenge, to be sure.
- A whole-body (systemic) allergic reaction, which can rarely include anaphylaxis — this is why testing is done where adrenaline and resuscitation are available.
- Feeling faint during the procedure.
- A delayed skin reaction appearing hours or days later.
Intradermal testing of drugs in particular carries a real, though small, risk of a systemic reaction including anaphylaxis. It must therefore be done by allergy specialists with resuscitation facilities, never as a casual or home test. Equally important, a positive result only shows sensitisation: ask the specialist what it means for you and whether a supervised challenge is needed to be certain.
Published figures to discuss
Skin tests provide evidence of sensitisation and must be interpreted in clinical context, not used to screen. Accuracy varies by allergen: for penicillin, for example, skin testing tends to have high specificity but lower sensitivity, so a negative test does not on its own exclude allergy. Intradermal testing is more sensitive than prick testing but less specific, and carries a small but real risk of a systemic reaction, which is why it is done in specialist settings.
| Figure | Reported range | How to interpret it | Source / confidence |
|---|---|---|---|
| Penicillin skin testing accuracy | In a systematic review, sensitivity around 30% and specificity around 97% | High specificity but low sensitivity means a positive is meaningful, but a negative test alone does not fully rule out allergy; a supervised challenge may still be needed. | NICE CG183 — Drug allergy: diagnosis and management (2014)nice.org.ukPublished figure |
| Systemic reaction during skin testing | Uncommon; intradermal drug testing carries a higher risk than prick testing | Reported rates vary and reliable exact figures are limited; the key point is that reactions can occur, so resuscitation facilities are essential. | NICE CG183 — Drug allergy: diagnosis and management (2014)nice.org.ukSource-linked context |
| False-positive intradermal result from irritant concentration | Recognised risk if non-validated concentrations are used | Drug-testing protocols should use accepted non-irritant concentrations and be interpreted by allergy specialists. | NICE CG183 — Drug allergy: diagnosis and management (2014)nice.org.ukSource-linked context |
| Negative intradermal test not replacing a challenge | Depends on drug and reaction type | A supervised provocation test may still be needed when proving tolerance is clinically important. | Guide sourcesClinical context |
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 beyond the test sites settling. Afterwards, what matters is understanding the result alongside your history, knowing what to avoid, and following up on any next steps such as a drug challenge or venom treatment.
- Itchy bumps and redness at the test sites that fade within a few hours.
- Mild soreness from the injections.
- A flare of usual allergy symptoms in the days after stopping antihistamines.
- Leaving with a clear result for immediate reactions, but sometimes needing a delayed read.
- Being asked to return for a challenge if the test alone is not conclusive.
Aftercare
- Avoid scratching the test sites; a cool compress or restarting antihistamines as advised can ease itching.
- Restart antihistamines once testing is complete, as directed.
- Follow the avoidance advice given, especially for confirmed drug or venom allergy.
- Carry any emergency medicines prescribed, such as an adrenaline auto-injector, and know how to use them.
- Attend any delayed reading appointment for drug tests.
- Make sure confirmed drug allergies are recorded clearly with your GP, pharmacy and on any allergy alert.
- Seek urgent help if a reaction develops after you leave.
- Antihistamines stopped for the advised number of days
- A clear account of your original reaction and any letters
- List of all medicines, including beta-blockers
- Confirmation of how long the appointment will take
- A way to get home and advice on driving
- Questions about what a positive or negative result will change
- Any existing emergency medicines to bring
Scars and how they heal
Intradermal testing leaves tiny needle marks and small raised bumps where the allergen is injected. These usually settle within a few hours and do not leave lasting marks. Occasionally a larger local reaction takes a little longer to fade.
⚠ Get urgent help if…
- Difficulty breathing, wheeze, or a tight or swollen throat after testing.
- Swelling of the lips, tongue or face.
- Feeling faint, dizzy or collapsing.
- A widespread rash or hives spreading beyond the test sites.
- A fast heartbeat with light-headedness.
- Any reaction developing after you have gone home — 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 intradermal test supports allergy to the tested drug or venom when it fits your history, helping the specialist advise on what to avoid and what is safe. A negative test makes allergy less likely but, because no skin test is perfect, the history and sometimes a supervised challenge are still needed.
The test cannot prove allergy on its own, cannot predict exactly how severe a future reaction would be, and a positive result to something you tolerate (sensitisation without allergy) is possible. This is why specialist interpretation matters.
Drug and venom test results reflect your immune state at the time of testing. Sensitisation can fade over years, and some drug allergies labelled in the past turn out not to be present on careful testing. Results may need repeating or confirming with a challenge if circumstances change or a clear answer is needed for future treatment.
Related tests, treatments or support
Intradermal testing is often combined with skin prick testing and specific IgE blood tests as part of a drug or venom allergy work-up, and may be followed by a supervised drug challenge. For venom allergy, it helps guide whether venom immunotherapy is appropriate.
Follow-up & long-term care
Follow-up depends on the findings. You may have a delayed reading for drug tests, a discussion of results with a plan for safe alternative medicines, or referral for a supervised challenge or venom immunotherapy. Confirmed allergies should be clearly recorded with your GP and pharmacy.
- Keeping confirmed drug or venom allergies clearly recorded everywhere relevant.
- Reviewing the need for repeat testing or a challenge if a clear answer is needed later.
- Maintaining and renewing any adrenaline auto-injector for confirmed venom allergy.
- Reassessing as part of any venom immunotherapy programme.
Repeat, follow-on and what comes next
- A negative or unclear result often needs a supervised challenge to give a definite answer for drugs.
- Delayed readings may be needed for some drug reactions.
- Sensitisation can fade over years, so old positive results may need rechecking.
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 the result in light of your history, with realistic next steps.
- A documented list of drugs to avoid and safe alternatives where relevant.
- An emergency plan and auto-injector for confirmed venom allergy.
- Confirmed allergies recorded with your GP, pharmacy and on alerts.
- Arrangements for any delayed reading, challenge or immunotherapy.
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:
- The seniority of the specialist and the time the appointment takes.
- How many drugs or allergens are tested, and at how many dilutions.
- Whether skin prick testing and blood tests are done alongside it.
- Whether a delayed reading appointment is needed for drug reactions.
- Whether a follow-up supervised challenge or immunotherapy assessment is required.
- The specialist setting and staffing needed to manage reactions safely.
- The fee for the appointment and how many allergens are included.
- Whether skin prick testing and blood tests are included or extra.
- Whether a delayed reading or follow-up visit is included.
- What a supervised challenge would involve and cost if needed.
- Confirmation that testing is done in a setting with resuscitation facilities.
- What happens, and what it costs, if the result is inconclusive.
- The cancellation policy.
On the NHS? Intradermal allergy testing is available on the NHS within specialist allergy and immunology clinics when clinically indicated; private testing is also offered but follows the same specialist standards.
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.
Consent traps
- Treating a positive result as proof of allergy without the history.
- Not explaining that a negative test may not fully exclude allergy.
- Performing testing without resuscitation facilities or adequate observation.
- Not warning about delayed reactions or the need for a follow-up challenge.
- Failing to clearly document confirmed allergies for future care.
Marketing red flags
- Offering intradermal 'allergy panels' for foods or general screening.
- Doing the test outside a properly equipped specialist setting.
- Promising a definitive diagnosis from the test alone.
- Not mentioning the risk of a systemic reaction.
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.
Questions to ask your medical professional
Take this to your consultation. A good specialist will welcome every one of these.
- Why is intradermal testing needed rather than a skin prick test or blood test alone?
- What will a positive or negative result actually change for my treatment?
- Could the result be a 'false positive' for something I actually tolerate?
- Will I need a supervised drug challenge to be sure?
- What emergency facilities and observation time do you have for this test?
- How should my confirmed allergy be recorded so future doctors know?
- 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?
Frequently asked questions
How is this different from a skin prick test?
Is it painful?
Why does it have to be done in a hospital or specialist clinic?
Does a positive test mean I am definitely allergic?
Do I need to stop my antihistamines?
Can I have it if I take a beta-blocker?
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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: BSACI guidelines for the management of drug allergy (Wiley) BSACI guideline — penicillin allergy diagnosis (beta-lactam) Anaphylaxis UK — Allergy testing Allergy UK — Food allergy testing and diagnosing Skin testing as a biomarker in drug allergy (Annals of Allergy, Asthma & Immunology) NICE CG183 — Drug allergy: diagnosis and management (2014)
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.
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