In the last century, diseases caused by overreaction of the immune system have increased steadily, particularly from around the 1970’s onwards. This has been especially the case for industrialised societies.

Allergies now affect as much as 50% of the industrialised human population.

Auto-immune diseases such as Type 1 Diabetes and Multiple Sclerosis (where the immune system reacts against the body’s own tissues) and other diseases involving inappropriate immune responses (e.g Crohn’s Disease) are prevalent in at least 10% of industrialised populations.

Although many different factors play a role, it is becoming clear that exposure to microbes has a vital part to play.