Omalizumab injection is used to decrease the number of asthma attacks (sudden episodes of wheezing, shortness of breath, and trouble breathing) in adults and children 6 years of age and older with allergic asthma (asthma caused by inhaling substances such as dander, pollen, and dust mites) whose symptoms are not controlled with inhaled steroids. It is also used to treat nasal polyps (swelling of the lining of the nose) in adults whose symptoms are not controlled with inhaled steroids. Omalizumab is also used to treat chronic hives without a known cause that cannot successfully be treated with antihistamine medications such as diphenhydramine (Benadryl), cetirizine (Zyrtec), hydroxyzine (Vistaril), and loratadine (Claritin) in adults and children 12 years of age and older. Omalizumab is not used to treat other forms of hives or allergic conditions. Omalizumab injection is in a class of medications called monoclonal antibodies. It works by blocking the action of a certain natural substance in the body that causes the symptoms of allergic asthma, nasal polyps, and hives.