Allergy Testing
Skin prick and blood tests used alongside clinical history to identify allergic triggers.
Last revised
Key takeaways
- Main tests: skin prick testing and specific IgE blood tests
- A positive test alone: indicates sensitization, not clinical allergy
- Most useful single change: Give a detailed history of what happened and how quickly.
- Commonest mistake: Commercial allergy tests sold direct to the public.
- See a doctor if any of the signs under "When to get help" below apply to you.
Why it matters
A positive test means sensitization, not allergy, which is why tests alone cannot diagnose and why unfocused testing causes harm.
The numbers, in one place
| Measure | Figure |
|---|---|
| Main tests | skin prick testing and specific IgE blood tests |
| A positive test alone | indicates sensitization, not clinical allergy |
| Gold standard | supervised oral food challenge |
| Not recommended | IgG testing, hair analysis, applied kinesiology, electrodermal testing |
What helps
- Give a detailed history of what happened and how quickly
- Ask for referral to a board-certified allergist rather than buying tests
- Understand that testing is guided by history, not the other way around
- Ask whether a supervised challenge is appropriate
What to avoid
- Commercial allergy tests sold direct to the public
- Excluding foods on the basis of a positive test alone
- Home reintroduction of a suspected allergen
In depth
Allergy tests look for IgE antibodies, the immune proteins that drive immediate allergic reactions. Skin prick tests place a tiny amount of allergen into the top layer of skin; if you have IgE to it, a raised itchy bump appears within about 15 to 20 minutes. Blood tests measure IgE to specific allergens in a laboratory. Both are accurate at detecting sensitization, but sensitization is not the same as clinical allergy. That distinction runs through every result.
Many people have IgE to a substance and suffer no symptoms when exposed. This is why a test result only makes sense when matched to a clear history of reactions. Testing a broad panel of foods in someone without a matching history commonly turns up positives that are not meaningful, leading to unnecessary avoidance, anxiety, and sometimes nutritional problems in children. Good testing is targeted, not exploratory. It answers a specific question raised by your history.
Some tests marketed directly to the public, including IgG food panels, hair analysis, applied kinesiology and electrodermal testing, have no scientific basis for diagnosing allergy. IgG antibodies to foods are a normal response to eating them. Allergy organizations advise against these tests because they lead to unnecessary restriction while missing genuine allergies, and because they can delay proper care. Some people spend considerable money on them and end up avoiding foods they could safely eat, while the real cause of their symptoms goes unexamined.
Causes and risk factors
- A history of reactions, which is the main reason to test
- Recent antihistamine use, which can block skin test results
- Extensive eczema or skin disease, which can make skin testing impractical
- Cross-reactivity between similar proteins, such as pollen and some fruits
- Testing too soon after a reaction, which may give false negatives for venom
How it is checked
An allergist starts with a careful history and then decides which tests, if any, are useful. For immediate reactions to foods, pollen, dust mites, pets, venom or some medicines, skin prick tests and specific IgE blood tests are standard. Intradermal tests, which inject allergen slightly deeper, are used mainly for venom and drug allergy. Component tests look at IgE to individual proteins within a food to refine risk.
For delayed skin reactions such as allergic contact dermatitis from nickel, fragrance or preservatives, patch testing is used instead: patches stay on the back for about two days and the skin is checked over several days. When results are uncertain, an oral food or drug challenge under medical supervision provides the clearest answer.
Related topics
- Food Intolerance: What the Evidence Actually Says (Digestive Health)
- What the Guidance Really Says About Allergens on Food Labels (Food Safety)
- The Evidence on Immune Function, Without the Hype (Immunity)
- The Evidence on Occupational Asthma, Without the Hype (Workplace Health)
Where to go next
- Allergy Testing: The Questions People Actually Ask
- The Short Guide to Allergy Testing
- Allergies: The Complete Guide
- Drug Allergy: Sorting the Evidence From the Noise
- What the Guidance Really Says About Asthma and Allergy
When to get help
Never attempt to reintroduce a food you have reacted to severely without medical supervision. Call 911 for swelling of the lips, tongue or throat, difficulty breathing or collapse. See your doctor for referral to an allergist if you have had any reaction involving breathing or circulation.
Where this comes from
- American Academy of Allergy, Asthma & Immunology — Allergy Testing
- National Institute of Allergy and Infectious Diseases — Food Allergy
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.