IGHE and Allergy: The characteristics of urticarial reactions reported by 410 subjects during β-lactam therapeutic courses were correlated to the results of a systematic allergy workup, which included skin tests, serum specific IgE (sIgE) assays and challenges.47 Urticaria with an onset within 1 hour (OR: 17, 95% CI: 9–31, P < 0.001) after the first dose (OR: 11, 95% CI: 6–20, P < 0.001), and with a maximal duration of 1 day (OR: 48, 95% CI: 14–157, P < 0.001) was significantly associated with allergy.