Teaching your children proper hygiene is important, there is no denying that, but they should not be protected from all contact with germs. In fact, according to a new study, published in the journal Nature Reviews Cancer, germ-free childhoods could play a part in the onset of the most common form of childhood leukemia, acute lymphoblastic leukemia (ALL).

Acute lymphoblastic leukemia is a rare type of cancer that affects white blood cells. It can affect both adults and children, although the NHS notes that in 85 percent of cases that affect children, it occurs in those younger than age 15, and most commonly between the ages of two and five.

If a child was born with the initial genetic mutation which puts them at risk for developing this type of cancer, as well as having reduced exposure to germs and infections in the early stages of life, then the hypothesis of this new research suggests that when they do eventually become exposed to common infections, their immune system will react in an abnormal way. Thus potentially causing chronic inflammation that could lead to acute lymphoblastic leukemia.

The study notes that a child should be exposed to bacteria within the first year so that their immune systems can develop properly. “For an immune system to work properly, it needs to be confronted by an infection in the first year of life,” Professor Mel Greaves, who has been studying the disease for over 30 years, told The Guardian. “Without that confrontation with an infection, the system is left unprimed and will not work properly.”

“The disease needs two hits to get going,” Greaves said of the biological events that must take place in order for ALL to develop. In addition to the first genetic mutation which happens in the womb, he says, “The second [mutation] comes from the chronic inflammation set off by an unprimed immune system.”

So, why is the link between the exposure to germs being explored?

The Guardian notes that over the last few decades in Europe and the UK, cases involving the disease have been increasing by around 1 percent a year. Greaves states: “The disease tracks with affluence.” This means that developed countries are more at risk than developing, with The Mirror noting a potential reason: “As countries industrialized and became wealthier the population tends to have smaller families, become cut off from extended families and live in more sterile environments" — social contact with other children is one of the ways that young children come into contact with germs.

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