The number of US children who suffered a seizure after swallowing someone else’s medication or illegal substance nearly doubled between 2009 and 2023, new research finds.

These types of seizures in people younger than 20 spiked from 1,418 in 2009 to 2,749 in 2023, according to an analysis of national poison data by University of Virginia researchers.

The poisonings most often involved over-the-counter antihistamines, prescription antidepressants, and painkillers and illegal synthetic cannabinoids.

Incidents rose annually by an average of 5%. Among people 6 to 19, cases doubled over the 15 years. There was a 45% increase in cases of children younger than 6.

“Seizure is one of the most severe symptoms a poisoned patient can experience, and children are particularly vulnerable,” said Dr. Conner McDonald from the University of Virginia School of Medicine.

“Depending on variables such as where a seizure happens, how long it continues and the pre-existing health of the child, seizures can lead to long-term damage or even death,” McDonald added.

His team attributed the “extremely worrying” rise in cases to easy access to diphenhydramine, commonly known as Benadryl, an over-the-counter antihistamine used to relieve allergy symptoms, the painkiller tramadol, the antidepressant bupropion (Wellbutrin) and synthetic designer drugs known as K2 or spice.

“Legal and illegal drugs can be bought online and shipped around the world,” McDonald explained. “Therefore, these drugs are becoming more available in homes and within the reach of children.”

The researchers — who presented their findings Wednesday at the European Emergency Medicine Congress in Copenhagen, Denmark — are calling for manufacturers to package the medications in child-resistant pill bottles and blister packs, where the user has to push the tablet through the foil, and for parents to safely store the medicine away from children.