Mustard-Induced Anaphylaxis in a 23-Month-Old Male: An Underrecognized Pediatric Food Allergen in the United States.

Mustard allergy is an uncommon but clinically significant cause of immunoglobulin E (IgE)-mediated food allergy that remains underrecognized in the United States despite its established allergenic potential in European pediatric populations. Mustard is frequently present as a hidden ingredient in condiments, sauces, and processed foods and is not currently required to be disclosed as a major allergen under the United States Food Allergen Labeling and Consumer Protection Act (FALCPA). We report a case of mustard-induced anaphylaxis in a 23-month-old male baby with a history of IgE-mediated egg allergy who developed diffuse urticaria, lip swelling, circumoral discoloration, and cough within minutes of isolated mustard exposure. Symptoms rapidly resolved following intramuscular epinephrine administration. Skin prick testing demonstrated marked mustard sensitization with a 15 mm wheal and 25 mm flare response. Prior pediatric studies have demonstrated that mustard allergy may present early in childhood and can provoke severe IgE-mediated reactions, including anaphylaxis. This case underscores mustard as an underrecognized trigger of pediatric food-induced anaphylaxis in the United States, highlights an important gap in current mandatory allergen labeling policy, and emphasizes the importance of maintaining clinical suspicion for uncommon food allergens in young children presenting with food-triggered systemic reactions.