001410 - A Rare Case: Anaphylaxis Induced by Melon Seed

Anaphylaxis is a severe, rapidly developing, and potentially life-threatening systemic allergic reaction whose incidence has increased across all age groups, including infants. Melon, watermelon, zucchini, pumpkin, and cucumber belong to the Cucurbitaceae family. Although melon allergy is the most frequently reported food allergy within this family, allergy to melon seed is extremely rare and has been reported only in a limited number of cases. Pumpkin allergy is also uncommon but may involve reactions to the peel, pulp, or seed. Shared seed storage proteins, particularly 2S albumins and 11S globulins, are considered the major allergens in these seeds and may account for potential cross-reactivity between poppy seed, pumpkin seed, and melon seed.

Here, we report a patient with known poppy seed and pumpkin seed allergy who developed anaphylaxis following exposure to melon seed.

A 15-year-old male presented to the emergency department with generalized pruritus, urticaria, and itching of the tongue and throat after accidental contact of his tongue with a melon seed while eating melon. Physical examination revealed generalized urticaria, uvular edema, and dyspnea. The patient was diagnosed with anaphylaxis and treated with a single intramuscular dose of 0.3 mg epinephrine, resulting in rapid resolution of symptoms. He was observed for 12 hours and subsequently discharged.

The patient tolerated melon flesh, watermelon, cucumber, and sunflower seeds without symptoms. His medical history revealed an episode of anaphylaxis at six years of age, occurring approximately five minutes after ingestion of ingestion of a baked product containing poppy seeds, characterized by generalized rash, lip swelling, and respiratory distress, which resolved after epinephrine administration. An epinephrine autoinjector was prescribed at discharge. At ten years of age, he developed oral itching following pumpkin seed consumption and subsequently avoided it. He tolerated wheat, rye, tree nuts, sesame, kiwi, banana, and legumes without reactions. He had never consumed watermelon seeds.

Serum tryptase measured during the acute episode was 33.6 µg/L, with a baseline tryptase level of 5 µg/L. Prick-to-prick testing was negative for melon flesh and sunflower seed, while positive reactions were observed for melon seed (16 x 10/40 mm), raw pumpkin seed (19 x 17/45 mm), roasted pumpkin seed (26x13/45mm), and watermelon seed (7x5/40 mm)

Although allergy to pumpkin seed and melon seed is rare, clinicians should be aware of potential cross-reactivity among seeds sharing common storage proteins, particularly in patients with poppy seed allergy. Recognition of such associations is essential for accurate diagnosis, appropriate dietary counseling, and prevention of life-threatening reactions.