[Oral Allergy Syndrome Following Soy Milk Ingestion in Patients with Birch Pollen Allergy]

Persons allergic to birch pollen often report oral and pharyngeal hypersensitivity to fruit and vegetables, due to immunological cross-reactivity between pollen and foods. This phenomenon is referred to as the oral allergy syndrome (GAS). Such cross-reactive antigen reactions mainly involve Bet v 1, which is the major birch-pollen allergen, and partially involve birch-pollen profilin Bet v 2. Soybean contains Bet v 1-related antigen (Gly m 4), and soy milk often causes the OAS with severe symptoms such as precordial and abdominal burning sensation because soy milk undergoes little denaturation, and this water-soluble liquid is consumed by most people rather quickly. We evaluated the frequency of the oAS after ingestion of soymilk and examined IgE antibodies to various allergens.

A total of 167 patients [122 women, 45 men; age range, 4-72 years (mean age, 32 years)], who had experienced GAS episodes and had IgE birch--pollen antibodies, were interviewed. Using the CAP system, we examined IgE antibodies to birch pollen and other allergens. Of 167 patients, 161 were examined for IgE antibodies to Bet v 1, Bet v 2, Gly m 4, and soybean. We evaluated the frequency of the GAS after soy milk ingestion based on reports by GAS patients with birch pollen allergy, and evaluated the positive rates of some of the IgE antibodies.

Among the 167 patients with birch-pollen allergy and GAS on ingestion of any of the foods, there were 16 cases (10%) with OAS following soy milk ingestion. In addition, the foods that caused OAS most often were apples (123 cases, 74%), peaches (67%), and cherries (55%), followed by pears (37%) and kiwi (37%). A higher CAP class for birch pollen, Bet v 1, Gly m 4, and soybean was associated with a higher prevalence of OAS to soy milk. Of 15 patients who had GAS on ingestion of soy milk and had birch-pollen allergy, 47% (7cases) were CAP class 1 for soybean and only 7% (case) was CAP class c2, whereas 93% (14cases) were CAP class 1 for Gly m 4, and 87% (3cases) were CAP class ≥ 2 for Gly m 4.

Among the birch-pollen allergic OAS patients, 10% had the OAS on ingestion of soy milk, and among these with birch-pollen allergy and the OAS on ingestion of soy milk, the positive rate for soy milk CAP was low, whereas that for Gly m 4 CAP was high.