Background: Current guidelines on chronic spontaneous urticaria (CSU) suggest a treatment based on a 3-step approach that aims at total symptom control, starting with H1-antihistamines. However, a significant number of patients present an antihistamine-resistant urticaria that must be treated with an alternative third-line therapy such as omalizumab. Methods: Patients with a history of CSU who did not respond to treatment with high doses of modern antihistamines were treated with 150 or 300 mg of omalizumab every 4 weeks. The response to treatment was recorded as complete (CR), partial (PR) or no response. A dose adjustment was proposed according to response. Results: We treated 47 CSU patients with omalizumab (40 females), of whom 39.5% had evidence of autoimmunity. The average number of treatments was 11.4 (range 2-87). All patients had been refractory to high-dose modern antihistamines. A CR was seen in 84.6% of patients who started with 300 mg and in 60% of those who started with 150 mg. Only 1 patient had no response to both the 150- and 300-mg doses. In 6 of the PR patients with 150 mg, a higher dose of 300 mg was proposed and 4 had a CR. Four patients discontinued the treatment. No severe adverse events were reported in the patients who finished the study. Discussion: Although good results were seen in both groups, CR rates were higher in those under a high-dose initial treatment. Our data strongly suggest that the therapy should be individualized.