Background Allergic diseases is a risk factor for leukemia but can also become a protective factor. Immune response activation induce preleukemia cells or allergic diseases increases the capacity of the immune system to detect and destroy aberrant cells.

Objective To determine the relationship of allergic diseases and atopy with the occurence of leukemia in children.

Methods A case–control study conducted in pediatric allergy immunology and hemato–oncology division November 2013 to February 2014. Children aged 3–17 years old with leukemia in the study group, and children without leukemia as the control group. The diagnosis of leukemia was established by bone marrow punction. Skin prick tests to assess atopy and International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire to assess allergic diseases. We used the x² test, and Fischer exact, logistic regression for statistical analysis.

Results Examination of 70 subjects at 35 of leukemia and 35 children without leukemia. One child found allergic disease and atopy in 13 children in the case group, while in the control group we found 9 allergic disease and atopy in 31 children. There was a relationship between allergic diseases with leukemia (P= 0.006). There was a significant relationship between atopy with leukemia (P= 0.0001). Atopy in children is a protective factor against leukemia (OR <1).

Conclusion There was significant relationship between allergic diseases and atopy with leukemia and atopy acts as a protective factor against leukemia.