The Effect of Omalizumab on Responses to Cat Allergen Challenge

Inclusion Criteria: * Ability to understand and provide informed consent * Male or Female (non-pregnant), age 18-50 * Females must be: Surgically sterile (hysterectomy, bilateral oophorectomy, bilateral tubal ligation), OR postmenopausal (at least 1 year since last menses), OR using a medically acceptable form of birth control throughout the duration of the study. * Clinical history of seasonal or perennial allergic rhinitis for at least two years, with or without mild persistent asthma * Positive puncture skin test greater than or equal to 5 mm diluent control * Positive Immunocap to Fel d 1 \> 0.35 kallikrein unit/L * Positive intranasal cat allergen challenge as defined by \> 5 sneezes or a tripling of measured nasal lavage mediators * In vitro assay of basophil responsiveness to cat allergen with greater than 20% histamine release * The use of antihistamines, cromolyn, leukotriene modifiers and other non-steroid (astelin and topical decongestants), nasal medications will be allowed, but they will be withheld for 5 days prior to each nasal allergen provocation session. Inhaled corticosteroids for mild asthma will be permissible. * No known contraindications to therapy with omalizumab Exclusion Criteria: * Asthma with forced expiratory volume at one second (FEV1) \< 80%, moderate to severe asthma classification per National Asthma Education and Prevention Program Expert Panel (NAEP) Standards (1997 National Asthma Education and Prevention Program Expert Panel Report II guidelines) * Serum IgE levels less than 30 IU/mL or greater than 700 IU/mL at the time of enrollment will be excluded * Unexplained elevation of erythrocyte sedimentation rate (ESR), hematocrit \< 32%, white blood cell (WBC) count 2400/microliter lower limit of normal, platelet \< 75000/microliter, creatinine \> 141.4 micromolar/L, or aspartate aminotransferase (AST) \> 100 IU/L * Body weight less than 30 kg or greater than 150 kg will be excluded. * Plans to become pregnant or breastfeed will be excluded from the study * A perforated nasal septum, structural nasal defect, large nasal polyps causing obstruction, evidence of acute or chronic sinusitis * A life expectancy less than 6 months * A terminal illness as determined by the investigator * A history of malignancy, anaphylaxis or bleeding disorder are also exclusion illnesses. * Mental illness or history of drug or alcohol abuse that, in the opinion of the investigator, would interfere with the participant's ability to comply with study requirements. * Inability or unwillingness of a participant to give written informed consent or comply with study protocol * Use of any investigational drugs within 8 weeks of participation * Contraindications to omalizumab include patients with a previous hypersensitivity to omalizumab * Recent recipient of any licensed or investigational live attenuated vaccine(s) within two months of study initiation such as flu mist. * Prior use of omalizumab * Frequent sinusitis (\>2/ documented episodes per year) or active sinusitis within 2 weeks of enrollment * Use of immunotherapy within the last 5 years