D1.74 - Sunflower Seed–Induced Anaphylaxis: Allergenic Characterization and Evidence of Cross-Reactivity with Niger Seeds

Sunflower seeds (Helianthus annuus) are an uncommon but increasingly recognized cause of systemic allergic reactions. Although inhalation-related sensitization has been reported, anaphylaxis following oral ingestion remains rare and poorly characterized. Given the botanical diversity of edible seeds and the structural conservation of storage proteins, cross-reactivity among seed sources may be clinically relevant.

A 35-year-old woman experienced anaphylaxis immediately after consuming bread containing sunflower seeds, despite previous tolerance. She reported mild respiratory symptoms when exposed to individuals consuming sunflower seeds and a past history of asthma and rhinoconjunctivitis during cohabitation with birds fed mixed seeds, including sunflower.Protein extracts were prepared from sunflower seeds, canary seed, Niger seeds (hydrosoluble and liposoluble fractions), and perilla seeds. Allergenic profiling was performed using SDS-PAGE and IgE-Western blot with the patient’s serum. Cross-reactivity was assessed using an IgE-Western blot inhibition assay.

Western blot analysis revealed a prominent ~13 kDa band in sunflower seed extract and in the hydrosoluble fraction of Niger seeds, showing strong IgE binding by the patient’s serum. This molecular weight is consistent with a 2S albumin (Hel a 15), a well-known plant storage protein frequently involved in food-induced anaphylaxis.Inhibition experiments demonstrated a marked reduction of the 13 kDa IgE-reactive band after serum preincubation with Niger seed extract, confirming cross-reactivity between both sources and indicating shared IgE epitopes within homologous storage proteins.

This case highlights sunflower seeds as a potential cause of food-induced anaphylaxis mediated by a 2S albumin. The observed cross-reactivity with Niger seeds underscores the presence of conserved epitopes among plant storage proteins and reinforces the need for molecular characterization of emerging allergenic sources. Clinicians should consider cross-exposures to botanically related seeds in the diagnostic workup of suspected seed allergies.