For most people, soy allergy is uncomfortable but not serious. Rarely, an allergic reaction to soy can be frightening and even life-threatening. Signs and symptoms of a food allergy usually develop within a few minutes to hours after eating a food containing soy.

Soy allergy symptoms can include:

  • Tingling in the mouth
  • Hives, itching or itchy, scaly skin (eczema)
  • Swelling of the lips, face, tongue and throat, or other parts of the body
  • Wheezing, runny nose or trouble breathing
  • Abdominal pain, diarrhea, nausea or vomiting
  • Redness of the skin (flushing)

A severe allergic reaction to soy — called anaphylaxis — is rare. It's more likely to occur in people who have asthma or are also allergic to other foods such as peanuts. Anaphylaxis causes more extreme signs and symptoms including:

  • Constriction of airways, including a swollen throat or a lump in your throat, that makes it difficult to breathe
  • Shock, with a severe drop in blood pressure
  • Rapid pulse
  • Dizziness, lightheadedness or loss of consciousness

Soy allergy in infants often begins with the introduction of a soy-based formula. Soy allergy may develop when a child is switched to a soy-based formula after an allergic reaction to a milk-based formula.

When to see a doctor

See your primary care doctor or a doctor who specializes in treating allergies (allergist) if you experience food allergy symptoms shortly after eating. If possible, see your doctor when the allergic reaction is occurring.

Seek emergency treatment if you develop any signs or symptoms of anaphylaxis, such as:

  • Constriction of airways that makes it difficult to breathe
  • Shock, with a severe drop in blood pressure
  • Rapid, weak pulse
  • Dizziness or lightheadedness
  • Drooling with an inability to swallow
  • Difficulty breathing
  • Full-body redness and warmth (flushing)
May. 20, 2011