Why are problems such as viruses, allergies and post-viral syndrome increasingly prevalent today? Is it true that a simple allergy might develop into a serious degenerative disease? What part does the immune system play in these processes - and how can it be affected by lifestyle? Jan de Vries places a strong emphasis on the importance of diet, and the effects of food additives and drugs. Did you know that schizophrenia can be treated through diet? Or that the lives of hyperactive children - and their parents - can be returned to normal by eliminating even a single item from their food intake? It has even been proven that diet and allergies can have an influence on crime. Together with other well-known nutritionists from around the world, the author has studied this phenomenon in detail and includes some illuminating case histories in this book.