Fountain Of Youth Meaning

(idiomatic) Anything reputed to have the power to restore health and vitality or to restore a youthful appearance.

Example:   Just watching the advertisement, you'd think the face cream was a fountain of youth.
1900, Charles W. Chesnutt, The House Behind the Cedars, Chapter I,
  Who has not known some even-tempered old man or woman who seemed to have drunk of the fountain of youth?