you need worms...,

Live Science | For instance, many fewer people are infected with worms than before.

"If you look back at the human race in the 20th century, every child and adult had worms in their gastrointestinal tracts," Weinstock said. "They were part of the ecosystem of the gut. As it turns out, worms are very potent at controlling immune reactions, in order to live happily ever after in the gut. Our theory is that when we started deworming the population, that is one factor that led to the rise in immunological diseases."

As part of this "hygiene hypothesis," Weinstock also notes that dirt roads, horses and cattle used to be far more prevalent in life than they are now.

"Our theory is that when we moved to this super-hygiene environment, which only occurred in the last 50 to 100 years, this led to immune disregulation," he said. "We're not saying that sanitation is not a good thing — we don't want people to jog up to river banks and get indiscriminately contaminated. But we might want to better understand what factors in hygiene are healthy and what are probably detrimental, to establish a new balance and hopefully have the best of both worlds."