If you are allergic to ragweed, and not taking certain medications, you will be asked to have blood drawn. We will perform experiments on your blood cells.

Adult ragweed allergic subjects will have blood drawn. Basophils will be enriched and stimulated with allergen and controls. Supernatants from these stimulations will be assayed for cytokines and histamine.

Inclusion Criteria:

• Ages 19 to 50
• At least 2 year history of ragweed allergic rhinitis
• Positive skin prick tests to ragweed >5 mm wheal diameter
• IgE <700 iU/m

Exclusion Criteria:

• Use of prohibited medications (e.g. antihistamine in past 7 days and topical or oral corticosteroids in past 1 month, beta-agonist or theophylline for 2 days.
• History of immunotherapy in the past 2 years
• Exposure to Omalizumab in the past 2 years
• Clinically significant non-allergic or perennial rhinitis to avoid mediator release due to environmental allergens
• Asthma other than mild intermittent
• Women of childbearing potential who are not on an accepted form of birth control, as well as women who are breastfeeding
• Known sensitivity to study drug Xolair
• Patients with severe medical condition(s) that in the view of the investigator prohibits participation in the study
• Patients with a previous history of cancer
• Use of any other investigational agent in the last 30 days