What Allergy Testing Is, and Why It Matters
Allergy Testing: what it is, why it matters, and what published guidance actually asks of you.
A positive test means sensitisation, not allergy, which is why tests alone cannot diagnose and why unfocused testing causes harm.
Key takeaways
- Main tests: skin prick testing and specific IgE blood tests
- A positive test alone: indicates sensitisation, 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 speak to a doctor" below apply to you.
The short answer
Skin prick and blood tests used alongside clinical history to identify allergic triggers.
Where it fits
This is part of Allergies. The rest of this page works through the figures and then the practical side.
The numbers, in one place
| Measure | Figure |
|---|---|
| Main tests | skin prick testing and specific IgE blood tests |
| A positive test alone | indicates sensitisation, not clinical allergy |
| Gold standard | supervised oral food challenge |
| Not recommended | IgG testing, hair analysis, kinesiology, VEGA testing |
What that means in practice
In everyday terms:
- Give a detailed history of what happened and how quickly
- Ask for referral to an allergy service rather than buying tests
- Understand that testing is guided by history, not the other way round
- Ask whether a supervised challenge is appropriate
What gets people into trouble
The mistakes that come up again and again:
- Commercial allergy tests sold direct to the public
- Excluding foods on the basis of a positive test alone
- Home reintroduction of a suspected allergen
Where to go next
- Allergy Testing: The Questions People Actually Ask
- The Short Guide to Allergy Testing
- Allergy Testing — the reference entry
- Drug Allergy: Sorting the Evidence From the Noise
- What the Guidance Really Says About Asthma and Allergy
When to speak to a doctor
Never attempt to reintroduce a food you have reacted to severely without medical supervision. Call 999 for swelling of the lips, tongue or throat, difficulty breathing or collapse. See a GP for referral if you have had any reaction involving breathing or circulation.
Where this comes from
- NICE — Food allergy in under 19s
- British Society for Allergy and Clinical Immunology — testing
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, summarised or generalised 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 a GP, 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 999.
Spotted something wrong? Report an error on this page. We correct on the page and say what changed.
