Lips that tingle after a handful of cashews. Hives after a milky coffee. A child who refuses eggs and gets a rash when he eats them anyway. Moments like these lead many people to ask about a food allergy IgE blood test, and it helps to know what such a test can and cannot say before ordering one.
This guide explains what IgE is, how the allergy panels in the BPR catalogue differ, and how results are read. All of them are processed by London Medical Laboratory (LML).
First, if a reaction is severe
A blood test is never the right tool in an emergency. The NHS advises calling 999 if the lips, mouth, throat or tongue suddenly swell, if breathing becomes very fast or difficult, or if someone feels faint or confused after contact with a food, and using an adrenaline auto-injector straight away if one has been prescribed (NHS, Anaphylaxis). For new or worrying symptoms that are not an emergency, the NHS suggests seeing a GP, who can refer to a specialist where needed (NHS, Food allergy).
What IgE is and what the test measures
IgE, immunoglobulin E, is a type of antibody. In an allergy, the immune system treats a harmless protein, from a food, pollen or animal, as if it were a threat and makes IgE against it. The LML describes allergy as the immune system getting confused between what is harmful, like bacteria and viruses, and harmless molecules in pollen, foods and other everyday particles.
An allergy blood test measures specific IgE: the amount of IgE that recognises one particular food or other allergen. Some panels also report total IgE, the overall level in the blood.
Sensitisation is not the same as allergy
This is the key point. The European Academy of Allergy and Clinical Immunology (EAACI) guideline on IgE-mediated food allergy explains that a positive specific IgE shows sensitisation, meaning the immune system has made IgE to that food. Many people are sensitised and still eat the food without trouble. That is why the guideline places a careful clinical history at the centre and reads test results against it (Santos et al., 2023). NICE guidance on food allergy in children and young people likewise starts with an allergy-focused clinical history before any test (NICE CG116).
In practice, a blood result is most useful when it answers a question raised by real symptoms, for example "is this reaction to peanut likely to be IgE related?", rather than as a broad search with no symptoms in mind.
The panels in the BPR catalogue
Allergy Complete
The LML describes this as the UK's most comprehensive allergy profile, testing 295 allergens with microarray technology from a single blood sample. Besides whole allergens, it looks at individual allergen molecules, which helps show cross-reactivity between related allergens. The EAACI guideline notes that testing allergen components can add information for some foods (Santos et al., 2023). According to the LML, a finger-prick home sample works as well as a venous one for this profile.
Extended Allergy Panel
This panel reports total IgE plus specific IgE to grass, weed, tree, dust mite and mould mixes and 40 single allergens. The food list includes milk, casein, egg white and yolk, peanut, almond, hazelnut, walnut, sesame, soya, rye flour, oat and maize, fish such as cod, salmon and tuna, and shellfish such as crab and shrimp, among others. It suits people whose symptoms could come from both food and environmental triggers.
Nut Panel
Total IgE plus specific IgE to 13 nuts and seeds: almond, Brazil nut, cashew, chestnut, coconut, hazelnut, macadamia, peanut, pecan, pine nut, pistachio, sesame and walnut. Useful when the question is focused on nuts.
Dairy IgE Allergy Panel
Specific IgE to cow's milk (raw and boiled), casein, goat's and sheep's milk, Cheddar, Swiss and Parmesan cheese and cheese mould, plus total IgE.
Single allergens
When the question is about one food, a single test such as Peanut IgE may be enough. The catalogue lists many single foods, each measuring specific IgE to that food alone.
A note on IgG "intolerance" tests
The catalogue also contains IgG panels, such as a dairy IgG panel. IgG is a different antibody and is not an allergy test. An EAACI task force concluded that food-specific IgG4 reflects normal exposure to foods rather than allergy or intolerance, and advised against using it for food-related complaints (Stapel et al., 2008). A later review reached a similar view on IgG testing for adverse reactions to foods (Kelso, 2018). For suspected food allergy, the tests to discuss are IgE based.
