What is ivig, and why might my doctor have told me I need to take it?

Gamma globulin. Ivig is intravenous gammaglobulin. This is a replacement therapy used commonly for immune deficiencies. It is given typically in an infusion center like a blood transfusion. Ivig also has immunomodulating activities so can also be used for kawasaki's disease as well as itp (immune throbocytopenic purpura).
IVIG. Ivig is pooled and purified igg antibody used in the treatment of primary immunodeficiency as well as off label use in rheumatologic, neurologic, oncologic diseases.