A teenager was arrested after a three-year-old was given laxatives by a group of boys in a park, police said today.
The boy was playing at the Pound Recreation Ground in Hoddesdon, Hertfordshire, when he was approached by three boys last Thursday, a police spokeswoman said.
They gave him laxatives which the toddler ate, believing them to be chocolate.
When his mother approached them, they were verbally abusive then left the scene, the spokeswoman said.
Police today said although the child was not seriously harmed, he was "quite ill" the next day.
Investigating officer DC Ian Minnis said: "Thankfully the child was not seriously harmed as a result of eating the laxatives, although he was quite ill the next day.
"We are treating this incident very seriously; to give a young child any form of medication not prescribed to them by a doctor could have had disastrous consequences."
He called for anyone in the area at the time to get in touch.
A spokeswoman said a 14-year-old boy was arrested in connection with the incident and has been bailed to return to Hoddesdon Police station on July 17.
She said one of the others boys was described as a white, aged 12-14 with ginger-blonde hair and of plump build. He was reported to be wearing a yellow top and had a strong Irish accent.
The third was white, between 10-11 years old, with short fair brown hair and of small build. He also had a strong Irish accent and was wearing a stripy t-shirt.