IVIG stands for Intravenous Immunoglobulin — a treatment made from pooled antibodies collected from thousands of blood donors and delivered through an IV. In PANS and PANDAS, the reasoning behind it is that flooding the system with healthy, normal antibodies may help modulate the harmful immune response that is causing brain inflammation. It does not treat an active infection — it addresses the immune dysfunction driving ongoing symptoms. IVIG is generally considered for children who have not improved adequately with antibiotics and initial anti-inflammatory treatment, or who present with a moderately severe to severe episode from the start. Responses vary — some children improve significantly after one course, others show partial improvement, and some require more than one course. It is not a first-line treatment for mild presentations.