COrticosteroids in acUte uRticAria in emerGency dEpartment

Inclusion Criteria: * Age \> 18 years * Isolated acute urticaria (acute hives): spontaneous urticaria, inducible urticaria * Acute urticaria with angioedema without laryngeal edema * Obtain patient's consent * Social security affiliation Exclusion Criteria: * Pregnancy or breastfeeding * Acute hives with anaphylaxis * Bradykinin angioedema * Angioedema without urticaria (hives) * Laryngeal edema with urticaria (hives) * Corticosteroid administration in the previous 5 days visiting the emergency department * Antihistamines greater than 1 tablet per day in the previous 5 days visiting the ED * Other treatment for urticaria : omalizumab, montelukast, ciclosporin A * Chronic urticaria before acute urticaria diagnosis * Atopic dermatitis * Eczema * Bullous pemphigoid * Acute exanthematous pustulosis * Diabetes mellitus * Gastrointestinal ulcer * Refusal to participate * Known allergy to the study drugs or formulation ingredients * Known Renal failure defined by creatinine clearance \< 10 mL/min or cardiac failure defined by ejection fraction \< 40%. * Corticoid use in 5 days prior to randomisation * Contra-indication to corticotherapy: * Any live vaccine * Psychotic states still uncontrolled by treatment limiting the participant's compliance with the research