Calls to poison control centers increased 17% from 2013 through 2014, according to an analysis of national poison data published Monday in the journal Pediatrics.
More than 22,000 children, mostly under age 3, were exposed to laundry packets in that period. About 30% of them were "already in or en route" to health care facilities when the call for help came in.
The data identified life-threatening problems that occurred only when children were exposed to packets of laundry detergent, including cases of children who stopped breathing, went into comas or suffered cardiac arrest. Two children died. The packets can also cause vomiting, throat burns and eye injuries.
The researchers said the findings demonstrate that laundry packets are more toxic than other detergents like laundry powder or dishwasher packets.
"Differences in chemical composition and concentration between laundry detergent packets and other types of detergents may account for the higher toxicity observed," they wrote.
The packets, introduced in the United States in 2012 as a less messy alternative to detergent powder, may attract children with their colorful designs and strong fragrances.
Some contain only granules, but others contain liquid, which when ingested doubled a child's odds of being admitted to a medical facility, the data show.
P&G, which makes detergents including Gain and Tide, has set up ad campaigns to emphasize safety in households that use the packets and says it has made its packaging more difficult for children to open.
"Accidents happen regardless of a laundry pac's color or design, so we are focused on reducing access to the packet and its contents," Shailesh Jejurikar, president of P&G Fabric Care, North America, said last year.
The researchers' recommendation: Parents of children under age 6 should use traditional laundry detergent to wash clothes.
They also noted an additional 14% increase in calls to poison centers concerning exposures to detergent packets for dishwashers.
The vast majority of children get into detergent packets at home, when soap containers aren't stored out of sight, locked in a high cabinet or monitored closely while open.