The philtrum is a vertical indentation in the middle area of the upper lip, extending in humans from the nasal septum to the tubercle of the upper lip.
The philtrum survives only as a vestigial medial depression between the nose and upper lip.
It has no apparent function.
The philtrum is formed where the nasomedial and maxillary processes meet during embryonic development.
If these processes fail to fuse fully, a cleft lip may result.
A flattened or smooth philtrum may be a finding in the fetal alcohol syndrome or Prader–Willi syndrome.
A broader than average philtrum is one of a cluster of physical attributes associated with autism spectrum disorders in boys.