Soy allergy
Mouth itching after a soy protein shake, mostly in spring? Soy is in a long list of foods, and in people with birch pollen sensitisation it can behave differently from what you would expect. Our test checks for IgE antibodies to four single soy proteins, as part of 300 allergens and allergen components.
- Group
- Food
- Season
- Year-round as a food; birch-related reactions are often reported more during birch season, March to May in central Europe
- Also known as
- soya, soybean, soya bean, Glycine max, Gly m 4, tofu, edamame
Where you meet it
- Tofu, tempeh, edamame, miso and soy sauce
- Soy milk, soy yoghurt and other plant-based dairy swaps
- Meat substitutes and protein powders (soy protein isolate)
- Bread, baked goods and chocolate (soy flour, soy lecithin)
- Processed meats, sauces, soups and ready meals
Two kinds of soy sensitisation
Soy contains storage proteins, such as Gly m 5 and Gly m 6, that survive heat and digestion. Sensitisation to these is what specialists pay most attention to.
Soy also contains Gly m 4, a protein that looks like the main birch pollen protein. People sensitised to birch can recognise Gly m 4 too. Most of those reactions are mild and limited to the mouth, but there are case reports of stronger reactions to lightly processed soy, such as soy drinks or protein powders. If you react to soy, a doctor should look at which proteins your result points to.
What people commonly report
Reactions people describe after soy include itching or tingling in the mouth, hives, swollen lips, stomach pain and, less often, wheezing.
Soy allergy is more common in young children than in adults. Adult reactions are often linked to birch pollen sensitisation.
Swelling of the lips or throat, or trouble breathing, is an emergency. Call 112 (EU) or your local emergency number.
Soy lecithin and soy oil
Refined soy oil and soy lecithin contain only traces of protein. Whether those traces matter depends on the person. If you have reacted to soy before, ask a doctor or allergist rather than relying on labels alone.
How our test checks soy
The lab measures IgE to four single soy proteins (molecular components). There is no whole soy extract on the panel. Your lab report gives each a measured value and class, from Negative to Very high. A result shows sensitisation, not a clinical allergy. Do not cut soy out, or change your diet, based on the result alone.
- Gly m 5 and Gly m 6: heat-stable storage proteins
- Gly m 8: a 2S albumin, another storage protein
- Gly m 4: a PR-10 protein similar to birch's Bet v 1
- Checked alongside birch pollen, peanut, pea, lentil and chickpea in the same sample
- Does not measure: IgG or food intolerance
Known cross-reactions
- Birch pollen
- Gly m 4 in soy resembles birch pollen protein Bet v 1. Birch-sensitised people can react to soy, mostly with mouth itching, sometimes more strongly to soy drinks or powders.
- Peanut
- Both are legumes. Shared antibodies are common in lab results; reacting to both is less common.
Sources
- EAACI Molecular Allergology User's Guide 2.0. Pediatric Allergy and Immunology, 2023.
- Severe oral allergy syndrome and anaphylactic reactions caused by a Bet v 1-related PR-10 protein in soybean, SAM22. Journal of Allergy and Clinical Immunology, 2002.
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300 allergens. One test.
A finger-prick sample at home, sent by post. A detailed lab report typically 5 days after the lab receives your sample, and our plain-English guide to reading it. €300, €1 per allergen.
Questions
Can birch pollen make me react to soy?
It can. A soy protein called Gly m 4 looks like the main birch protein, so birch-sensitised people sometimes react to soy, usually with mouth itching. Talk to a doctor if you have had stronger reactions.
Is soy milk a safe swap if my result shows cow's milk?
Not automatically. Some people are sensitised to both. Ask a doctor before you swap one milk for another.
Does a soy result mean I should stop eating soy?
Not on its own. A result shows IgE sensitisation. Discuss it with a doctor, especially if you eat soy regularly without symptoms.