French scientists are warning parents not to use chemical shampoos to rid their children of head lice. The results, they say, could be an increased risk of developing leukemia.

The French research group INSERM conducted the study, looking at 280 children who had recently been diagnosed with leukemia. Their mothers were interviewed on a number of subjects, including any use of insecticidal shampoos, as well as the use of pesticides and fungicides in the home and garden.

Based on responses to the interview questions, scientists said they can conclude that using insecticidal shampoos could almost double the risk of developing leukemia. They also found the risk of developing the disease was almost twice as likely in children whose mothers said they had used insecticides in the home while pregnant and after birth.

The research did not specify any of the lice shampoo brands used by the children, but cited ingredients such as malathion, pyrethroid and lindane which are often in such products.

Leukemia is a malignant disease of the bone marrow and blood. It is characterized by the uncontrolled accumulation of blood cells. The Leukemia and Lymphoma Society estimates there were nearly 35,000 new cases of leukemia in the United States in 2005. Most cases occur in older adults, with more than half of all cases occurring after age 67.