A candy striper was a young female volunteer who was enrolled in a youth training program at a hospital in the late 20th century. These volunteers assisted the nursing staff with patient needs. The nickname for these volunteers came from their red and white striped pinafores and hats, which resembled striped peppermint candy. They were required to display their photo id on their uniforms.
In 1986, while members of the HMS Bounty's crew were attempting to rescue Pavel Chekov from Mercy Hospital's 20th century medicine, a few candy stripers were walking in the hallways. (Star Trek IV: The Voyage Home)