Nevertheless, consider measuring drug-specific IgE levels in serum for the assessment of sensitization to relevant allergens ascertained from the history of the anaphylactic episode.45 Although IgE-mediated anaphylaxis occurs after re-exposure to an allergen, cross-reactivity to a component of the drug may occur after the first exposure in isolated cases, for example, galactose allergy and cetuximab. The gene discussed is IGHE; the disease is anaphylaxis.