[Acute urticaria associated to omalizumab treatment in a child with asthma].

Omalizumab is a monoclonal anti-IgE antibody indicated as an adjuvant therapy in moderate persistent allergic asthma in the United States or severe asthma in Europe. In 2009 the European Medicine Agency approved its indication in patients older than six years. In clinical practice, it is considered a safe drug, however local reactions at the injection site, anaphylaxis, or delayed diagnosis of Churg-Strauss syndrome are warned. We report the case of an 8 year-old female patient diagnosed with moderate persistent allergic asthma, who met the criteria for treatment with omalizumab. During the initial injection the patient had erythema and wheal at the site of injection, and presented generalized and fluctuating urticarial within 24 hrs, with partial response to antihistamines. During her second injection, a half of the initial dose was given, and she presented a wheal and flare locally, accompanied by headache, dizziness, sweating, pallor, without loss of consciousness. She has continued receiving this medication, without adverse reactions. It is important to evaluate other substances included in the omalizumab vial, since some of them, as histidine, may be the causative factor of adverse effects.