While urticarial can occur alongside asthma when it is associated with atopy, especially food allergy, it most frequently occurs as an “idiopathic form” where no known external allergies are found; nevertheless anti-IgE therapy can still be highly effective in such patients event in the absence of autoantibodies against IgE or FcεR1 (see Chapter by Sarbjit Saini in this series of reviews). The gene discussed is IGHE; the disease is allergic disease.