A case of a girl who presented at age 12 years with idiopathic cold urticaria is described. Her reactions to the cold became progressively more severe over a period of approximately 2 years, despite therapy with H1 antagonists and a type 1 receptor for cysteinyl leukotrienes receptor antagonist. She began to experience systemic symptoms on immersion in ocean water. She was atopic and had moderate persistent asthma. A trial of anti-IgE resulted in complete resolution of her urticaria and its associated manifestations. These findings should prompt a reexamination of the potential pathogenetic role played by IgE and its high-affinity receptor on mast cells in idiopathic cold urticaria.