Most parents want the same things for their children—to grow up a happy and overall healthy person. But in order to do that, you have to make sure earlier on that you’re doing everything you can to keep their wellness in top-notch shape. Right?

Surprisingly, no. Actually, constantly monitoring germs could be doing the opposite, and be detrimental to your kids’ health.

According to a new study published in the journal Nature Reviews Cancer, children who grew up in a germ-free household may be more likely to develop acute lymphoblastic leukemia (ALL).

ALL is the most common type of childhood cancer, and most often develops in children zero to four years old, though older children and even adults can also get it as well.

A blood cancer, ALL builds up in the blood in a short period of time, spreading to other parts of the body, most commonly the lymph nodes, liver and nervous system. Chemotherapy is most often used to treat it.

There is a caveat to the study: Children must have the genetic mutation before birth that predisposes them to the risk of developing acute lymphoblastic leukemia.

Besides having that mutation, the study only applies to children who’ve been exposed to infections later on in their childhood—after they lived in a super-clean home before that, during a time where they never got infections.

So basically, you raise a child to never, ever get sick — e.g., you wash your hands after every pat of the dog before touching your child, or freak out if they drop a piece of food on the floor, etc. — but then later on in their childhood – say, when they enter school – they can no longer be as protected and they get sick. Plus, they were born with the genetic mutation that predisposes them to getting ALL. Then that child is most at risk for actually developing ALL.

The author of the study, Mel Greaves, professor at the Institute of Cancer Research, started to study the matter after becoming interested in why or how seemingly healthy children get this type of leukemia and whether or not it’s preventable.

He dived into over 30 years of research on everything from genetics to cell biology, immunology, epidemiology and more and this is what he found.

“This body of research is a culmination of decades of work, and at last provides a credible explanation for how the major type of childhood leukaemia develops,” says Greaves. “The research strongly suggests that [this cancer] has a clear biological cause, and is triggered by a variety of infections in predisposed children whose immune systems have not been properly primed.”

The idea here is that newborns and small children should be exposed to infections because it’ll build their immune systems so that they can fight off germs later, and if you avoid this and never expose them to germs, later infections might trigger leukemia (in those who have the genetic mutation).

However, other experts aren’t quite sure about this result, and say that more research needs to be done to make this kind of conclusion— and that it’s still important to be safe with young kids and their hygiene.

Check out this video below to learn more about the unexpected danger that comes from giving your kids a “germ-free” childhood.

What do you think of this study? Do you believe in exposing babies to germs earlier or raising them in a completely germ-free household?