Flaxseed allergy: insights from a case series.

Background. Flaxseed allergy is a rare and potentially underdiagnosed condition. In recent years, sensitization to flaxseed has increased due to its growing presence in the human diet. This study presents three distinct cases of flaxseed allergy and discusses the strengths and limitations of current diagnostic tools in identifying this emerging allergy. Methods. Each case underwent a detailed clinical history followed by an allergological evaluation using in vivo testing (skin prick-to-prick) and in vitro methods (serum specific IgE testing with singleplex and multiplex immunoassays) for flaxseed and other suspected seeds or tree nuts. Results. Case 1: A male patient, previously diagnosed with pumpkin seed allergy, experienced multiple episodes of urticaria and angioedema following ingestion of bread containing unspecified dark seeds. Testing revealed sensitization to flaxseed, pumpkin, sunflower, sesame seeds and storage proteins from soy, walnut, and hazelnut. Case 2: A male patient developed cutaneous symptoms after ingesting an energy bar. Testing showed positivity only to flaxseed, while results for other seeds and tree nuts were negative. Case 3: A female patient with repeated episodes of labial angioedema and anaphylaxis, initially misdiagnosed with sesame allergy, was found to be allergic to flaxseed. Conclusions. Flaxseed allergy remains a rare but emerging condition that is difficult to diagnose, partly due to its frequent omission from ingredient labels and the absence of specific allergenic molecules in commercial diagnostic tests. Future regulatory consideration should evaluate the inclusion of flaxseed among priority food allergens.