The child described in the vignette has classic symptoms of anaphylaxis: respiratory difficulties, urticaria, and generalized discomfort. Many patients who experience anaphylaxis describe an impending sense of doom. Studies have demonstrated that patients who do not have an urticarial rash are at much higher risk of death than those who have one.
The most likely cause of this child's anaphylaxis is a food allergy. Because she has been receiving amoxicillin for several days, it is unlikely that the reaction is due to that medication. The history of disliking eggs and usually not eating them provides a clue to the potential food allergy; many children who have a food allergy will refuse to eat the offending food long before the food is identified as an allergen.
The primary cause of anaphylaxis in children is foods; bee stings and drugs are much less likely causative agents. The primary food allergens in infants and toddlers are eggs, milk, wheat, and soy. Among older children, shellfish, fish, nuts, and peanuts are also common triggers.
The mainstay of therapy for anaphylaxis is administration of subcutaneous epinephrine. Studies have demonstrated that patients in whom administration of the initial epinephrine is delayed have a higher mortality rate than those who are promptly given epinephrine. Patients usually have symptoms within 10 minutes of ingestion, but may not develop all the symptoms of anaphylaxis for up to 2 hours after the ingestion. Accordingly, epinephrine should be given at the first sign of symptoms, and the child should be transferred promptly to a medical facility.
Food poisoning does not cause respiratory difficulties or urticaria. Serum sickness can cause urticaria and general discomfort, but it is not abrupt in onset and does not have respiratory symptoms. Viral urticaria is not seen acutely in a previously well child.
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