Soy allergy symptoms can include: 1  Tingling in the mouth. 2  Hives; itching; or itchy, scaly skin (eczema) 3  Swelling of lips, face, tongue and throat, or other body parts. 4  Wheezing, runny nose or breathing difficulty. 5  Abdominal pain, diarrhea, nausea or vomiting.  Skin redness (flushing)