Book excerpt: This book discusses the various mechanisms by which food can trigger autoimmunity, thus turning a patient's own immune system against him. Readers will learn about the vital role of oral tolerance in immunity, the history of food allergy testing, difference between food allergy and food immune reactivity, the gut-brain-immune system axis, and discover how the blood-brain barrier and its integrity is connected to neuroautoimmunity and neurodegeneration. It ends with concrete workable suggestions on how to repair or restore broken immunity, or maintain a healthy immune system. This book is for medical or health care practitioners whose patients have puzzling symptoms and test results that are difficult to explain; it will help practitioners give patients the answers, diagnosis, care and treatment that they deserve, and can help to prevent, halt, or even reverse the course of autoimmune disease in patients, saving them from what could be an unhappy lifetime of suffering