Pseudo-allergy screening (food colourings and additives)

Pseudo-allergies are reactions that resemble an allergy but do not involve IgE antibodies. They are triggered, among other things, by colourings and additives in food. The pseudo-allergy screening examines 15 substances in three groups (pools): pool 1 with quinoline yellow, sunset yellow, azorubine, amaranth and cochineal red A; pool 2 with erythrosine, patent blue, indigo carmine and brilliant black; pool 3 with potassium metabisulphite, sodium benzoate, sodium nitrite, sodium salicylate, tartrazine and glutamate. The test uses living immune cells from EDTA blood, which is therefore sent to the laboratory by express delivery.

What the pseudo-allergy screening measures

The laboratory uses the CAST method (cellular antigen stimulation test). White blood cells, including the basophil granulocytes, are brought into contact with the groups of substances. If the cells react, they release sulphidoleukotrienes – inflammatory messengers formed from the arachidonic acid of the cell membrane. Their amount is then measured and compared with untreated cells. The test thus captures a cellular reaction, regardless of whether IgE is involved. Which pool was conspicuous is stated in the report; for individual substances within a pool, the laboratory offers a separate test.

Pseudo-allergy screening conspicuous – what happens in the body?

A conspicuous reaction shows that immune cells respond to substances in the pool by releasing messengers. In the body, additives can act in several ways: some activate mast cells and basophils directly, so that histamine is released. Salicylates and some azo dyes interfere with arachidonic acid metabolism and shift it towards leukotrienes, which narrow the airways and make blood vessels leakier. Sulphites can give rise to sulphur dioxide, which irritates the airways. It is typical that symptoms depend on the amount and only occur above a certain dose: hives, skin redness, swelling, a runny or blocked nose, headache or abdominal discomfort after ready-made foods and drinks.

Pseudo-allergy screening unremarkable – what does it mean?

If the release of messengers remains low for all three pools, the immune cells in the test did not react measurably to these substances. Additives not included in the screening, such as other preservatives or natural salicylates in fruit and spices, are not assessed by this. Because pseudo-allergic reactions depend strongly on dose, accompanying circumstances such as infections or painkillers and on the state of the skin and mucosal barrier, a reaction can still occur in everyday life. The informative value of cellular tests for pseudo-allergies is considered debated in the specialist literature. Similar symptoms can also arise from histamine in foods or from an IgE-mediated allergy, which are described on their own pages.

The interpretation is given in your report.