It’s true for half the species. Women have those stripes. Each cell of a woman’s body only needs one active copy of the X chromosome, so when they’re very young each cell will turn off a copy at random. Each cell that cell divides into will have the same copy turned off, so patterns develop. Those patterns of cells absorb and reflect UV light differently based on which copy is turned off. If you can see in UV light, women are stripey.

Edit to add: after further reading it appears that men have Blaschko’s lines too, although more faintly. If so, the X-inactivation explanation is wrong, or at least incomplete.