Yellow mealworm (Tenebrio molitor): A rare cause of chronic urticaria

This report presents a unique case of chronic urticaria (CU) caused by a food allergy to mealworm. A 10-year-old boy experienced daily itchy urticarial rashes for three months, accompanied by swelling, especially in the morning. Despite high-dose second-generation antihistamines, montelukast, a hypoallergenic diet, and intermittent steroids, symptoms persisted. Routine investigations, including hemogram, thyroid function tests, and autoantibodies, were normal. Total IgE level was elevated (715 kU/L), but skin prick tests showed no sensitivities. Component-resolved diagnosis revealed a reaction to yellow mealworm (Tenebrio molitor, 0.53 kUA/L). Investigation uncovered daily bread consumption prepared from flour stored in non-heat-resistant sacks, where mealworms proliferated. Symptom resolution followed dietary elimination of contaminated flour, enabling treatment tapering. Tenebrio molitor thrives in high-temperature storage and is increasingly used as a protein source. Cross-reactivity with shrimp allergens is documented. This case highlights the role of environmental factors in CU and the utility of component-resolved diagnostics. Identifying yellow mealworm as a rare CU cause emphasizes the importance of comprehensive evaluation in persistent cases.