Sunflower Seed–Induced Anaphylaxis With Immunoglobulin E Reactivity to <scp>2S</scp> Albumins and Novel 60  <scp>kDa</scp> Antigen Identified by Immunoblot Analysis

Sunflower seed allergy is uncommon, and reports of severe systemic reactions, such as anaphylaxis, are limited, particularly in Japan where sunflower seeds are not routinely consumed. A 38-year-old woman developed throat discomfort, dyspnea, and generalized urticaria within minutes of ingesting cookies containing sunflower seeds and was diagnosed with anaphylaxis. Her medical history included bronchial asthma and pollinosis caused by Japanese cedar and cypress. Skin prick testing (SPT) showed a strong positive (4+) reaction to sunflower seeds, while the results were negative for mugwort, cashew nut, and macadamia nut. Basophil activation testing (BAT) demonstrated marked upregulation of CD203c expression on basophils in response to sunflower seed extract, with an activation rate of 50.6% at 10 μg/mL, whereas the positive and negative controls showed activation of 34.5% and 1.8%, respectively. Serum analysis in immunoblotting revealed immunoglobulin E (IgE) binding to both the precursor and mature forms of 2S albumin, as well as to a novel 60 kDa antigen in sunflower seed and pollen extracts. Long-term exposure to sunflower seeds during childhood and adolescence while keeping birds may suggest sensitization via inhalation or skin contact rather than through oral ingestion or cross-reactivity with related pollens. 2S albumins are seed storage proteins found in high concentrations in several nuts and seeds and are major allergens capable of causing severe systemic reactions due to their resistance to heat processing and digestive enzymes. For the diagnosis and severity assessment of sunflower seed allergy, immunoblotting to detect IgE reactivity to 2S albumin is essential in addition to SPT and BAT. Detection of IgE antibodies against antigens of identical molecular weight in both sunflower seeds and pollen indicates the presence of shared antigens, suggesting that caution is necessary not only for sunflower seed ingestion but also for exposure to pollen.