There were no reports of weight gain or weight loss in clinical trials with Xolair.

Weight gain is more likely to be caused by corticosteroids, hydroxyzine, or antihistamines that may also be used to treat allergic asthma or hives.

Xolair (omalizumab) is an antibody that may be used to treat allergic asthma that is

• Moderate-to-severe
• Persistent
• Not adequately controlled by inhaled corticosteroids
• In adults and children aged 6 and over who have had a positive skin test to an allergen or who react to an allergen that is present in their environment year-round.

Xolair is also approved to treat:

• Urticaria (hives) in adults and children aged 12 and older who have already tried antihistamines without success
• Nasal polyps in adults aged 18 years and older.

Xolair is administered by injection under the skin (subcutaneously) once every two to four weeks. The dosage of Xolair is based on body weight.

If your weight does change while taking Xolair, talk with your doctor who can recommend diet and exercise tips to encourage a healthy weight.