Despite safety advances in product packaging, tens of thousands of U.S. preschoolers visit the emergency room each year for accidental poisonings from medications, supplements and household products, researchers reported Monday.

Investigators with the U.S. Consumer Product Safety Commission in Bethesda, Maryland, found that in 2004, more than 86,000 children younger than 5 years old were treated in an ER for an accidental poisoning. In more than half of those cases, the child ingested a product that, by law, must have child-resistant packaging.

The findings suggest that the design of such packaging could be improved, the CPSC researchers report in the journal Pediatrics. The investigators also advise parents to keep all potentially toxic substances out of the reach of children, whether the packaging is child-resistant or not.

A range of potentially toxic household substances are required to have child-resistant packaging — including prescription oral drugs, some common over-the-counter medications (like aspirin and other painkillers) and certain household products, such as lighter fluid, paint solvents and antifreeze.

However, many other potentially dangerous household staples do not fall under this regulation. These include detergents and other cleaning products, personal care products, and many non-prescription medications and supplements.

In the current study, the federal researchers found that 55 percent of child poisonings involved a regulated product — most often an oral medication. In cases where an unregulated product was the culprit, cleaning products were most commonly involved.

"Despite advances in recent years and the decrease in unintentional fatal poisonings, unintentional child poisonings remain an important public health concern," write CPSC investigators Robert L. Franklin and Dr. Gregory B. Rodgers.

But while child-resistant packaging is obviously not foolproof, the researchers note, studies show that such packaging has cut fatal and non-fatal poisoning rates by about 40 percent over the years.

That suggests that adding safer packaging to currently unregulated products could help further reduce child poisonings, according to Franklin and Rodgers.

Still, they add, child-resistant packaging alone is clearly not enough. For one, "child-resistant" is not the same as "child-proof," and some children will be able to open the products.

"Parents and caregivers," the researchers write, "should always be encouraged to keep toxic substances out of the reach of children, even when they are already in child-resistant packaging."