ABSTRACT
Investigations into the effects of environmental agents concentrate on definite events that can be measured without dispute, such as death or cancer. The immune system provides the body's defensive interface with the environment. The immune system is second only to the brain in complexity. In allergy, the immune system has, as it were, got hold of the wrong idea. In its continuous search for threats to the system, it has picked up a piece of pollen, house dust, house dust mite faeces, or other substance, and has decided that it must be fought. The human immune system has developed over the course of some 2 million years, on the top of a mammalian immune system that goes back some 40 million years. The autonomic nervous system, which controls the internal organs, including heart and blood vessels, also innervates the spleen and bone marrow, tissues that are home to the immune system.
