Last reviewed: July 2026
What You Need to Know
- A positive test does not mean you’re allergic. It means you’re sensitized. In one study of peanut-sensitized children, only about 22% turned out to be genuinely allergic when properly challenged. This is the single most misunderstood fact in food allergy.
- The oral food challenge is the gold standard — and it’s the only test that gives you a definitive answer.
- Test results do not predict how severe a reaction will be. A high number is not a “worse allergy.”
- Intradermal testing should not be used for food allergy. Skip to the section below — this page used to recommend it, and that was wrong.
- Never test without a reason. Broad allergy panels in people with no reaction history generate false positives and lead to years of pointless food avoidance.
The Most Important Distinction: Sensitized ≠ Allergic
Skin prick tests and blood tests both measure the same underlying thing: whether your immune system has made IgE antibodies against peanut.
But having those antibodies doesn’t mean you’ll react when you eat it.
- Sensitized = your body has made IgE against peanut. Common. Often harmless.
- Allergic = you actually have a clinical reaction when you eat it.
The gap between these two is enormous. In a study of children who tested peanut-sensitized, only 22.4% were actually peanut-allergic when given a supervised food challenge. Peanut-specific IgE levels overlap substantially between people who genuinely react and people who don’t.
This is why testing without a reason is harmful. A child with no history of reacting to peanut, who gets a positive test on a broad panel, may be placed on a lifetime of unnecessary avoidance, epinephrine, and anxiety — for an allergy they never had. And with early introduction now the guidance for preventing peanut allergy, unnecessary avoidance may actively cause the problem it was meant to prevent.
Test because there’s a history. Not because a panel was available.
The Tests
1. Skin Prick Test (SPT)
A drop of peanut solution on the skin, pricked through with a small lancet. If a raised, itchy bump (a wheal) develops within about 15–20 minutes, that’s a positive.
- Fast — results in under half an hour
- Sensitive — good at ruling allergy out. A negative test is genuinely reassuring.
- Poor at ruling it in — lots of false positives
- Size matters, somewhat. A wheal of 8 mm or more carries roughly a 95% positive predictive value for true peanut allergy. Smaller wheals are far less conclusive.
Practical: you must stop antihistamines several days beforehand — they suppress the reaction and produce a false negative. Ask the clinic exactly how long.
2. Specific IgE Blood Test
Measures peanut-specific IgE in blood.
- Useful when skin testing isn’t possible — severe eczema, dermatographism, or when you can’t stop antihistamines
- A peanut sIgE of 14 kU/L or above carries around a 95% positive predictive value
- Lower levels are much less conclusive
A terminology note: the old RAST test is obsolete. Modern labs use ImmunoCAP or similar. If someone offers you a “RAST,” their information is out of date.
3. Component Testing (Ara h 2) — the real advance
This is the most significant development in peanut diagnosis, and the previous version of this page predates it entirely.
Instead of testing against whole peanut, component testing measures IgE against individual peanut proteins — and they mean very different things:
| Component | What it suggests |
|---|---|
| Ara h 2 (and Ara h 1, 3, 6) | Storage proteins. Heat-stable. Associated with genuine, potentially severe peanut allergy. Ara h 2 is the most useful single marker. |
| Ara h 8 | Similar to a birch pollen protein. Usually means cross-reactivity, not true peanut allergy — typically mild, mouth-only symptoms, if any. |
Why this matters: it can separate the child with true peanut allergy from the child with hay fever whose immune system merely recognizes a birch-like protein in peanut. Those two children have been treated identically for decades. They shouldn’t be.
The honest caveat: the AAAAI practice parameter suggests Ara h 2 as the best single test if only one is used — but it advises against routinely adding component testing on top of a skin prick or IgE test to boost accuracy. It has the greatest specificity but lower sensitivity than SPT and sIgE. It’s a targeted tool, not an automatic add-on. Your allergist decides whether it adds anything in your case.
4. Oral Food Challenge (OFC) — the gold standard
Completely absent from the old version of this page, and it’s the only test that actually settles the question.
Under medical supervision, you eat gradually increasing amounts of peanut while being monitored. If you react, you’re allergic. If you don’t, you’re not.
- It is the definitive answer. Everything else is probability.
- It must be done in a properly equipped medical setting with epinephrine and staff on hand. Never at home.
- It carries a real risk of triggering a reaction — that’s the point, and it’s why supervision is non-negotiable
- It’s time-consuming and resource-heavy, which is why allergists use the tests above to decide who genuinely needs one
If you or your child has been avoiding peanut for years on the basis of a blood test alone — ask your allergist whether a challenge is appropriate. A significant number of people are carrying a diagnosis they don’t have.
⚠️ The Correction: Intradermal Testing
The previous version of this page described intradermal testing — injecting peanut solution into the skin — as a normal step when the skin prick test is negative.
That is not current practice, and it is not safe.
NIAID expert-panel guidelines recommend against intradermal testing for food allergy, because it carries a greater risk of systemic allergic reactions than skin prick testing. It also produces a large number of positives in people with no symptoms at all.
Intradermal testing has a legitimate role — for venom and some drug allergies. It does not have one in food allergy testing. If a clinician proposes it for peanut, ask why.
Atopy patch testing is likewise not a validated tool for IgE-mediated food allergy. (Patch testing is for contact dermatitis — a different mechanism entirely.)
🚫 Tests to Avoid Entirely
These are marketed heavily — often directly to worried parents — and they are not recommended by allergy bodies:
- IgG or IgG4 food panels (“food sensitivity testing”) — IgG indicates exposure, not allergy. These generate long lists of “problem foods” and cause needless restriction. Not validated. Not recommended.
- Hair analysis
- Applied kinesiology (muscle testing)
- Electrodermal / vega testing
- Cytotoxic testing / ALCAT
- Lymphocyte proliferation assays
- Total serum IgE (as an allergy test — it doesn’t tell you what you’re allergic to)
And a warning about large panels: broad allergy screens are not recommended, because they multiply false positives, cause unnecessary food restriction, and generate a cascade of further testing. The number of people who have eliminated foods they were never allergic to, on the basis of a panel nobody should have ordered, is enormous.
What the Numbers Don’t Tell You
Test results do not predict severity.
This is counterintuitive and worth sitting with. A study that challenged peanut-sensitized children found no relationship between IgE levels — to whole peanut or to any individual component — and either the severity of the reaction or the amount of peanut needed to trigger one.
A “high” number does not mean a worse allergy. A “low” number does not mean a safe one.
What tests estimate is the probability that you’re allergic. Not how bad it will be if you are. Which is why everyone with confirmed peanut allergy carries epinephrine regardless of what their numbers say. See allergic reactions: what to do in an emergency and peanut allergy bracelets.
Allergies Can Be Outgrown — Get Retested
Roughly 20% of children outgrow peanut allergy. Testing is not a life sentence handed down once.
If your child has been avoiding peanut for years, periodic reassessment — potentially including a supervised food challenge — is appropriate. Ask your allergist. The difference between “allergic” and “was allergic” is a very different childhood.
Who Should Be Tested
Yes:
- A genuine reaction after eating peanut
- Severe eczema or egg allergy in an infant — these children should be assessed before peanut introduction (everyone else should just introduce it early — see what “peanut-free” means)
- Unexplained anaphylaxis
No:
- “Just to check” with no reaction history
- As part of a broad panel with no clinical question behind it
An allergist should order and interpret this — not a general panel, not a direct-to-consumer kit. Your primary care doctor can refer you; see getting the most from your doctor and do you know your medical rights.
If your child has asthma alongside food allergy, that’s not a side issue — uncontrolled asthma is a major risk factor for fatal anaphylaxis. See asthma: help your child breathe easier, and talk to your pediatrician.
The Bottom Line
Tests give you a probability. A history gives you context. Only a supervised food challenge gives you an answer.
And a positive test, on its own, in someone who has never reacted, is not a diagnosis — it’s a question.
Related Reading
- Allergic Reactions: Symptoms and Emergencies
- Peanut Allergy Symptoms
- Peanut Allergy Treatment
- Peanut Allergy Bracelets
- What Does “Peanut-Free” Mean?
- Understanding Food Labels
- The ABCs of Picking a Pediatrician
Sources: AAAAI/ACAAI 2020 Practice Parameter on peanut allergy diagnosis · NIAID expert panel guidelines on food allergy diagnosis · peer-reviewed literature on component-resolved diagnostics (Ara h 2) and oral food challenge outcomes · published guidance on non-recommended allergy tests.
This article is for information only. Allergy testing should be ordered and interpreted by an allergist.
