Evaluation of subcutaneous immunotherapy with birch pollen extract for pollen-food allergy syndrome

Some patients with pollen-food allergy syndrome (PFAS) develop systemic symptoms along with oral allergy syndrome upon ingesting processed foods as well as raw fruits and vegetables. This study aimed to investigate the efficacy of subcutaneous immunotherapy with birch pollen extract for patients with PFAS associated with soybean allergy. Subcutaneous immunotherapy with birch pollen extract was introduced in 6 patients with PFAS caused by alder/birch pollen and soybean allergy. An oral food challenge for ingestible amount of soy milk was performed before and 1 year after initiating subcutaneous immunotherapy with birch pollen extract. Before the treatment, the median intake of soy milk was 1.5 mL (interquartile range [IQR], 1–2 mL). One year after the treatment initiation, the median intake of soy milk increased significantly to 150 mL (IQR, 20–200 mL). Systemic reactions occurred in 4 of 6 patients in the rapid escalation phase of the treatment. The results thus suggest that subcutaneous immunotherapy with birch pollen extract could be beneficial for patients with PFAS associated with soybean allergy despite concerns regarding systemic reactions.