Uses: This medication is used to treat moderate to severe asthma in adults and children over 12 years of age. It works by blocking your immune system's natural response to allergic triggers that can lead to an acute asthma attack. This action on your immune system (specifically immunoglobulin E-IgE), helps keep your air passages open and, over time, it keeps your asthma in better control. This medication does not work immediately and should not be used for the quick relief of an acute asthma attack.