Testing
Food allergy, intolerance and sensitivity
These three words get used interchangeably, including by people selling tests. They describe different things, they need different investigations, and getting the distinction wrong is the most common reason people spend money and end up no wiser.
The distinction that matters
A food allergy is an immune reaction mediated by IgE antibodies. It is usually fast, often within minutes, and can be serious: swelling, hives, wheeze, in the worst case anaphylaxis. It is diagnosable with established tests.
A food intolerance is not an immune reaction at all. It is usually an enzyme or absorption problem, lactose intolerance being the familiar example. Symptoms are digestive, slower to appear, and unpleasant rather than dangerous.
Food sensitivity is the loosest of the three and the least well defined. It usually describes delayed, non-IgE reactions that people notice but that no single test reliably identifies. That vagueness is precisely why it attracts so much poor testing.
What I test, and why
Testing follows the history rather than replacing it. What you react to, how quickly, how reproducibly, and what else is going on in your gut and immune system will usually narrow the field before any blood is taken.
Where genuine IgE allergy is suspected, specific IgE blood testing and skin prick testing are well established and I use them. Where the picture points to intolerance, the useful investigations are different: enzyme function, absorption, and the state of the gut itself, because intolerance is often secondary to something else rather than a fixed fact about you.
Structured elimination and reintroduction remains the most informative approach for delayed reactions, and often the only one that gives a clear answer. It is slower and less satisfying than a test result, and it is more reliable.
Tests I will tell you not to bother with
IgG food antibody panels, sold widely as food sensitivity tests, are not a reliable guide to what is causing your symptoms. IgG antibodies to food are a normal finding and largely reflect what you eat. Most professional allergy bodies advise against using them diagnostically.
The same caution applies to hair analysis, applied kinesiology and bioresonance testing for food reactions. If you have already paid for one of these, bring the results and we can talk about them, but I will not build a treatment plan on them.
I would rather lose the sale of a test than sell you one that cannot answer your question.
Common questions
Can I just do an at-home test kit?
You can, and many people arrive having done one. The difficulty is that most home kits measure IgG rather than IgE, which tells you what you have been eating rather than what you are reacting to. People then eliminate a long list of foods unnecessarily. If you want a home test to be useful, it needs to be measuring the right thing for the reaction you are actually having.
How long does elimination and reintroduction take?
Usually several weeks for the elimination phase and then a structured reintroduction one food at a time. It requires patience and reasonably careful record keeping. I will give you a written protocol rather than a vague instruction to avoid things.
I react to almost everything. What does that mean?
Reacting to a very wide range of foods often points away from the foods themselves and towards something underlying: gut barrier problems, histamine handling, mast cell activity or bacterial overgrowth. In that situation, testing each food individually tends to be the wrong strategy.
Do I need a referral?
No. If your history suggests true IgE allergy with any risk of severe reaction, I will make sure you are under appropriate NHS allergy care as well, rather than instead.
Related
Discuss your case with Dr Greenland
A short discovery call is the usual starting point. It costs nothing, and it is the fastest way to find out whether this approach fits your situation.