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Soy Allergy

Also known as: Soya allergy, Soybean allergy

Soy allergy is common in infants and young children, particularly those with cow's milk allergy. Most reactions are mild, but severe reactions can occur. Soy is one of the top food allergens and is found in an enormous range of processed foods.

Category

Food Allergies

Severity

Mild to Moderate

Prevalence

0.3–0.4% of children; less common in adults.

Symptoms

Airways & Breathing

  • Runny nose
  • Nasal congestion

Skin

  • Hives
  • Eczema
  • Itching

Digestive

  • Nausea
  • Vomiting
  • Diarrhoea

Systemic / Other

  • Anaphylaxis (rare)
  • FPIES (food protein-induced enterocolitis) in infants

How It's Diagnosed

  • Skin prick test and specific IgE to soy
  • Oral food challenge under supervision
  • Component testing: Gly m 4 (relevant for birch-pollen sensitised patients, raw soy triggers oral allergy syndrome)

Avoidance Strategies

  • Soy is ubiquitous: tofu, tempeh, miso, soy milk, soy sauce, edamame, soy protein
  • Check labels for soya, soy lecithin (E322), textured vegetable protein (TVP), hydrolysed soy
  • Many meat substitutes, protein shakes, and processed foods contain soy
  • Soy oil and highly refined soy lecithin are usually well tolerated — confirm with your allergist

Cross-Reactivity

  • Peanut — both are legumes; mild structural similarity but most tolerate one without reacting to the other
  • Birch pollen (Bet v 1) — Gly m 4 in raw soy may cause oral allergy syndrome in birch-sensitised individuals

Soy and infant formula

Soy-based infant formulas were once recommended as an alternative for cow's milk allergic infants. However, because 10–15% of cow's milk allergic infants are also soy allergic, current guidelines prefer extensively hydrolysed or amino-acid-based formulas for most infants with CMA.

Discuss the appropriate formula with your paediatric allergist.

Related Allergens

Peanut Allergy

Food Allergies

Cow's Milk Allergy

Food Allergies

Back to Allergy Library

Medical disclaimer

This page is for educational purposes only. Allergy diagnosis and management must be carried out by a qualified allergist. Do not attempt to test yourself with suspected allergens. Always carry prescribed emergency medications and follow your written action plan.

Reviewed 2026-06-01 · Looms Medical Team