Despite major advances in health care, over recent decades we’ve been battling an ever-growing epidemic of once rare allergic and autoimmune diseases.

Today, more than 17 million people in the U.S. alone struggle to maintain one of their body’s most basic functions — breathing. Another 50 million are now thought to be coming under regular attack by their own immune systems.

A similar pattern has emerged in modern cities and communities across the planet. Even as we’ve improved hygiene, developed antibiotics and implemented vaccination programs, the number of walking wounded has skyrocketed. It’s a desperate and puzzling situation that has sufferers and scientists alike scrambling for answers.

In recent years a number of leading medical researchers have come to a startling theory about the cause of this epidemic of “modern” diseases. Called the Hygiene Hypothesis, it suggests the war against germs and worms being waged in the hygiene-obsessed western world may be triggering serious illness in hundreds of millions of people.

It may be that unless we lay down our arms and stop attempting to live in a sterile biological exclusion zone, we may prove to be worse enemies to ourselves than almost all the microscopic life-forms we are being taught to fear.