Allergy Testing: Separating Myth From Guidance
Allergy Testing: what people commonly get wrong, set against what published UK guidance says.
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.
What the guidance actually says
Here is what guidance actually publishes. The rest of the page is measured against it.
| 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 |
Where people go wrong
Common beliefs that the figures do not bear out.
- Commercial allergy tests sold direct to the public
- Excluding foods on the basis of a positive test alone
- Home reintroduction of a suspected allergen
What to do instead
- 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
The part that is genuinely uncertain
Guidance changes, and it changes because evidence does. The figures above reflect current UK guidance from the bodies named at the foot of this page; where those bodies revise their position, theirs is the account to follow rather than this one.
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.
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