15 Common IgE Foods Test

Specific IgE to cow's milk is directed against caseins, beta-lactoglobulin, and alpha-lactalbumin. Sensitisation reflects prior allergen exposure and T-helper-2 class switching rather than disease per se; the detected IgE is the circulating counterpart of allergen-bound IgE on mast cells and basophils. Casein-dominant IgE tends to track persistent, heat-stable reactivity, whereas IgE confined to heat-labile whey proteins may accompany tolerance of baked milk.

A positive cow's milk sIgE supports, but does not establish, an IgE-mediated milk allergy in a child or adult with a consistent immediate reaction. In the absence of a compatible history it most often represents clinically silent sensitisation. Component testing and, where indicated, a supervised oral food challenge remain the arbiters of true clinical reactivity.

Egg white carries the major allergens ovomucoid (Gal d 1), ovalbumin, ovotransferrin, and lysozyme. Ovomucoid is heat- and digestion-resistant and correlates with reactivity to cooked egg, while IgE confined to the heat-labile fractions often accompanies tolerance of baked egg. Egg white IgE in infancy is also an epidemiological marker of atopic trajectory.

Egg white sIgE is the usual first-line serological marker in suspected egg allergy. The titre offers a probabilistic, not deterministic, read on clinical reactivity, and the heat-stable component ovomucoid informs whether baked-egg introduction may be considered under specialist supervision rather than from the panel result alone.

Wheat specific IgE recognises water-soluble albumins and globulins and the alcohol-soluble gliadins, among them omega-5 gliadin (Tri a 19), the dominant allergen in wheat-dependent exercise-induced anaphylaxis. IgE sensitisation to wheat is immunologically and mechanistically distinct from the T-cell-mediated, HLA-restricted response of coeliac disease and from non-coeliac wheat sensitivity.

Wheat sIgE supports evaluation of immediate IgE-mediated wheat allergy and exercise-induced reactions, but it does not diagnose coeliac disease, which requires tissue transglutaminase and endomysial serology on a gluten-containing diet. Cross-reactivity with grass pollen profilins frequently produces positive wheat IgE without clinical food reactivity.

Soy allergens include the storage proteins Gly m 5 (beta-conglycinin) and Gly m 6 (glycinin) and the Bet v 1 homologue Gly m 4. Gly m 4 sensitisation commonly arises secondary to birch-pollen allergy and tends to cause mild, oral symptoms, whereas storage-protein IgE is more often associated with systemic reactivity.

A positive soy sIgE in a birch-sensitised patient frequently reflects pollen cross-reactivity rather than primary soy allergy. Distinguishing the two shapes risk counselling, and the whole-extract panel result cannot make that distinction on its own — component resolution is required.

Whole peanut extract contains the storage proteins Ara h 1, 2, 3, and 6, the lipid transfer protein Ara h 9, and the Bet v 1 homologue Ara h 8. Ara h 2 is the allergen most predictive of systemic reactivity, while isolated Ara h 8 sensitisation is usually a benign consequence of birch-pollen allergy.

Whole-extract peanut IgE is sensitive but poorly specific for clinical allergy because it captures benign cross-reactive sensitisation. A positive whole-extract result on a 15-food screen should prompt component-resolved testing (notably Ara h 2) before any dietary restriction, and a reaction history remains central to the assessment.

The dominant fish allergen is the muscle calcium-binding protein parvalbumin (Gad c 1 in cod), which is heat- and digestion-stable and highly cross-reactive across bony fish species. Cooking rarely abolishes reactivity, and parvalbumin content varies between species, which underlies the variable cross-species tolerance some patients report.

Cod sIgE serves as a marker of bony-fish sensitisation; a positive result frequently predicts reactivity to multiple fish because of parvalbumin homology. It does not predict shellfish reactivity, which is a biologically unrelated tropomyosin-driven sensitisation, so the two must be assessed separately.

Shrimp reactivity is driven chiefly by tropomyosin (Pen a 1 / Pen m 1), a heat-stable muscle protein conserved across crustaceans and molluscs and homologous to invertebrate tropomyosins in house dust mite and cockroach. This homology produces frequent cross-reactivity and positive IgE in mite-sensitised patients who tolerate shellfish.

Shrimp sIgE marks crustacean sensitisation but, because of tropomyosin cross-reactivity with inhalant allergens, a positive result in a mite-allergic patient may not reflect clinical shellfish allergy. Interpretation requires the ingestion history; the panel value alone cannot separate true food allergy from cross-sensitisation.

Almond allergens include storage proteins (amandin/Pru du 6), lipid transfer protein (Pru du 3), and profilin. Whole-extract almond IgE is less well characterised than other tree nuts and shows appreciable cross-reactivity with other Rosaceae and tree-nut proteins, so isolated positivity is of uncertain clinical weight.

Almond sIgE contributes to a tree-nut sensitisation picture but, given frequent cross-reactivity and limited component standardisation, a positive whole-extract result carries modest specificity. It should be weighed against the clinical history and, where a confident diagnosis is needed, a supervised challenge rather than acted on in isolation.

The class score is a derived, semiquantitative translation of the measured specific IgE concentration into ordinal bands. It compresses a continuous immunoassay signal into categories for reporting convenience; the underlying concentration, not the band, carries the quantitative information, and small concentration changes can cross a class boundary without clinical meaning.

Rising class or concentration raises the statistical probability of clinical reactivity for a given allergen but does not grade reaction severity and does not predict anaphylaxis. The class score is a screening-level output: it frames which allergens merit focused history, component testing, or challenge, and should never be read as a severity index.