Immune tolerance refers to the failure of an immune system to respond to a certain immune-response causing agent known as an antigen. This happens when the immune system has previously been sensitized with that antigen, and it already recognizes it as its own. The immune system fights against any foreign bodies that attack it, in an attempt to remove it from the body.

Scientific research shows that exposing your child to these antigens will give him protection against most life-threatening diseases, especially those that occur during the early stages of life as you will learn in this section.