Patient description: The patient is a 15-year-old boy with asthma diagnosed a year ago. He presents with shortness of breath, chest tightening and cough. According to his mother, he didn't respond to the usual corticosteroid inhaler. He was admitted to the emergency department with diagnosis of severe asthma exacerbation. He is a candidate for general corticosteroid therapy. Spirometry revealed a forced expiratory volume in the first second (FEV1) of 60% of the predicted. His past medical history is non-significant. His family history is significant for asthma in his mother and his uncle. He used to be treated with combination of inhaled corticosteroids and Zafirlukast.

Clinical trial eligibility criteria: eligible ages (years): 6.0-17.0,  Asthma Combined body weight (as measured at the screening visit) and total serum IgE level (as measured within 3 months of the screening visit) suitable for omalizumab (Xolair®) dosing A diagnosis of asthma by a clinician made more than 1 year prior to recruitment; participants who received an asthma diagnosis by a clinician less than 1 year prior to recruitment must report that their respiratory symptoms were present for more than 1 year prior to recruitment Having a requirement for at least 100 mcg fluticasone 100 mcg twice a day or equivalent at the Assumption of Care Visit AND who meet at least one of the following i. ≥1 asthma-related exacerbations, separated by at least two weeks, requiring treatment with a systemic corticosteroid course in the previous 12 months ii. ≥1 asthma-related overnight hospitalizations in the past 12 months A positive prick skin-test to at least one perennial allergen (i.e. dust mite, cockroach, mold, cat, dog, rat, mouse) documented at the screening visit or at a ICAC study visit within 12 months of the screening visit Primary place of residence is in one of the pre-selected recruitment census tracts Able to perform spirometry Parent or legal guardian is willing to sign the written informed consent (age appropriate) prior to initiation of any study procedure Willing to sign the assent form, if age appropriate A history of chickenpox or receipt of the chickenpox vaccine Insurance which covers costs of medications; and  Participants who meet any of the following are not eligible for enrollment but may be reassessed Assigned to a treatment of less than 100 mcg fluticasone twice a day or equivalent at the Assumption of Care Visit Pregnant or lactating. Females of child-bearing potential (post-menarche) must be abstinent or use a medically acceptable birth control method throughout the study (e.g. oral, subcutaneous, mechanical, or surgical contraception) Clinically significant laboratory abnormalities (not associated with the study indication) at the screening visit Platelet count less than 100 x 10^9/L at the screening visit Currently participating in another asthma-related pharmaceutical study or intervention study or who have participated in another asthma-related pharmaceutical study or intervention study in the month prior to Recruitment Living with a foster parent: exception -not applicable if participant is able to provide consent Does not have access to a phone (needed for scheduling appointments) Plan(s) to move from the area during the study period Has previously been treated with omalizumab (Xolair®) within 1 year of recruitment