A paramedic was punched in the face in a "sickening attack" when two teenage robbers demanded she hand over drugs and tried to grab her medical bag.
The woman, who is in her 30s, was providing care to someone late on New Year's Eve when she was approached by two boys on Coventry Close in Stevenage.
The pair - thought to be around 14 or 15 years old - demanded she hand over any drugs she had with her and tried to grab her medical bag.
When that failed, one of the boys punched her in the face.
"This was a sickening attack on an emergency service worker who was simply doing her job," said Det Con Kirsty Rusbridge, of Hertfordshire Police.
"Thankfully she wasn't seriously injured, but this was understandably a very frightening ordeal for her.
"Emergency service workers should be able to go about their jobs without fearing for their safety and this kind of shocking behaviour will simply not be tolerated."
The boys were wearing dark clothing, including a black puffer jack, and one of them wore glasses.
Police are appealing for anyone who was in the Coventry Road area of Stevenage around 11.45pm on New Year's Eve who have seen the two boys, or could have useful dash-cam footage.