Scientists have a new theory about why more people suffer from allergies than ever before. It’s not that we’re too clean or too dirty but that when we get dirty we get dirty with the wrong kind of dirt.

For years, some researchers have believed that allergies were on the rise because modern homes are too clean. Since our immune systems were not sufficiently interacting with dirt and microbes, this theory held, our bodies were overreacting to allergens like pollen and peanuts.

The more recent theory proposes that avoiding allergies is not just a matter of being exposed to microorganisms and dirt. You have to live amongst the proper dirt — the paleo dirt in which our ancestors rolled.

“The rise in allergies and inflammatory diseases seems at least partly due to gradually losing contact with the range of microbes our immune systems evolved with, way back in the Stone Age,” says Graham Rook, co-author of a scientific report on this subject from the International Scientific Forum on Home Hygiene (IFH). “Only now are we seeing the consequences of this, doubtless also driven by genetic predisposition and a range of factors in our modern lifestyle — from different diets and pollution to stress and inactivity. It seems that some people now have inadequately regulated immune systems that are less able to cope with these other factors.”

But don’t have a dirty house in order to lower your risk of allergies. That won’t work and might make you sick. The bugs in today’s dirt are not the “old friends” that were the beneficial microbes Stone Age people lived with.

“How we can begin to reverse the trend in allergies and CID (chronic inflammatory diseases) isn’t yet clear,” says Rook. “There are lots of ideas being explored but relaxing hygiene won’t reunite us with our Old Friends — just expose us to new enemies like E. coli O104.”

“One important thing we can do,” adds report co-author Sally Bloomfield, “is to stop talking about ‘being too clean’ and get people thinking about how we can safely reconnect with the right kind of dirt.”