WASHINGTON (AFP)--Dozens of popular children's bath products marketed in the U.S. contain two cancer-causing chemicals, a consumer safety watchdog group said in a report published Friday.

The Campaign for Safe Cosmetics commissioned an independent laboratory to test 48 top-selling children's products for 1,4-dioxane and 28 of them for formaldehyde.

Twenty-three of the 28 products tested for the study were shown to contain formaldehyde, and 17 of the 28 contained both formaldehyde and 1,4-dioxane.

Among those were the highly popular Johnson's Baby Shampoo by Johnson & Johnson (JNJ), L'Oreal Kids Extra Gentle 2-in-1 shampoo from L'Oreal SA (12032.FR) and Pampers Kandoo foaming hand soap by Procter & Gamble Co. (PG), which contained enough formaldehyde to trigger a skin reaction in sensitive people, the Campaign for Safe Cosmetics said in its report.

Thirty-two of the 48 products tested, or 67%, contained 1,4-dioxane.

Used for embalming corpses and, in the U.S., as glue in chipboard, formaldehyde is a by-product of a preservative added to the products to prevent bacteria growth and extend their shelf-life.

The 1,4-dioxane chemical is used as a foaming agents in some products.

According to the U.S. National Cancer Institute, studies of workers exposed to formaldehyde have linked the chemical to cancers of the nasal sinuses, nasopharynx, brain and possibly leukemia.

The U.S. Consumer Product Safety Commission has said that even trace amounts of 1,4-dioxane give "cause for concern," while the Environmental Protection Agency and Department of Health and Human Services have both identified dioxane as causing cancer in animals and as a "probable human carcinogen."

"If chemicals are causing cancer in animals, we really shouldn't be putting them on babies' heads," Stacy Malkan of the Campaign for Safe Cosmetics said.

"While the levels found in the products are low, little bits of carcinogens add up in all these products," she said, adding that the findings of the study gave cause for concern because "children are more vulnerable to the toxic effects of chemicals."