Background: We report a case of IgE-mediated hypersensitivity to lemon seed. We demonstrate for the first time a pattern of cross-sensitisation between seeds of citrus hybrid species from similar ancestral species origins. Case report: Described is a case of a 26-year-old female with recurrent anaphylaxis on exposure to lemon seed with sensitisation shown on prick to prick testing. Prick to prick testing was also performed to a variety of citrus fruit seeds and edible foods from additional notable families of the Sapindale order. Conclusion: In cases of unexplained or recurrent anaphylaxis in adult patients, citrus seed allergy should be considered.