Since 1970, the number of allergy sufferers around the world has risen dramatically. the current estimate of people with some kind of allergy is an astounding 30-40%. the direct cause of increase are unclear, but most researchers attribute the growing figure to a combination of environmental and social changes resulting from the effects to rapid post-war industrialization, modernization and globalization. increased industrial pollution, crowded cities, small poorly ventilated apartments with air conditioning and new synthetic building materials, dietary changes more cosmetics and modern medicine are all blamed as the main contributors. paradoxically, over-cleanliness has also been identified as a cause. some researchers claim the widespread use of home cleaning agents and their resulting germ-free environments have weakened children's immune systems and created vulnerable adults. perhaps most striking, however, is the growing number of food allergies. modern global trade has allowed foods formerly unknown to people to become easily accessible. this has resulted in more allergic reactions due to the increase in opportunities for people to eat new foods their bodies nave never encountered before.