BACKGROUND: Lupine allergy is caused by ingestion of the flour of a plant called Lupinus albus, a member of the Leguminosae family. Lupine allergy has been described in adult patients previously known to have peanut allergy (cross-reactivity). OBJECTIVE: To describe the first case of an anaphylactic reaction caused by ingestion of lupine flour in a pediatric patient without a known peanut allergy. METHODS: Symptom assessment, nutritional history, and skin and blood tests. RESULTS: An otherwise healthy 8-year-old boy had nose and eye discharge followed by facial edema and difficulty breathing 30 minutes after eating an industrially prepared waffle containing eggs, sugar, and lupine flour. He had no history of food allergy and was eating a normal diet, including peanuts and other legumes. Results of skin prick tests using commercial extracts were positive to peanuts and negative to eggs, soy, and nuts; results of a prick-to-prick test using lupine flour were strongly positive (+ + + +). His total IgE level was 1,237 UI/mL. Specific IgE antibodies were positive to lupine seeds (20.8 kU/L) and peanuts (> 100 kU/L). CONCLUSIONS: To our knowledge, we describe the first case of an anaphylactic reaction after ingestion of lupine flour in a child without known allergy. In the case of peanut allergy or any anaphylactic reaction without evident cause, especially after industrially prepared food ingestion, lupine should be considered in the list of allergens tested. Lupine is increasingly used in industrially prepared food but is not regularly declared in the composition, leading to difficulties in allergen avoidance.