Children who attend daycare or playgroups cut their risk of the most common type of childhood leukaemia by around 30%, a study estimates.
Researchers reviewed 14 studies involving nearly 20,000 children, of which 6,000 developed acute lymphoblastic leukaemia.
It is thought early infections may help the body fight off the disease.
The University of California, Berkeley study will be presented to a leukaemia conference in London. Leukaemia is the most common cancer found in children in the industrialised world, affecting about one in 2,000 youngsters.
ALL accounts for more than 80% of leukaemia cases among children, and most often occurs in those aged between two and five. Scientists believe that for most types of childhood leukaemia to develop, there must first be a genetic mutation in the womb, followed by a second trigger - such as an infection - during childhood.
However, it is also thought that contracting some childhood infections - which are often readily spread in environments such as playgroups where children are in close contact with each other - may prime the immune system against leukaemia.
Conversely, if the immune system is not challenged in early life, this is thought to raise the risk of an inappropriate response to subsequent infections, making the development of leukaemia more likely.
Source - BBC