No, Xolair is not a steroid, but it does prevent inflammation. Xolair works by preventing IgE from binding to IgE receptors on mast cells and basophils, preventing the release of chemicals such as histamine, and reducing the number of IgE receptors on basophils. Histamine can cause inflammation and symptoms such as difficulty breathing (wheezing), a runny nose, watery eyes, tissue swelling, itchy skin, and hives. Xolair belongs to the class of medicines known as monoclonal antibodies. It may also be called a selective immunosuppressant.