*All* humans have stripes. In fact, everyone’s stripes follow the exact same general patterns. These stripes, called Blaschko lines, are invisible most of the time, but certain skin (and other) conditions bring them out.
More than a century ago, in 1901, German dermatologist Alfred Blaschko noticed that many of his patients’ rashes and moles seemed to follow similar formations, almost as though they were tracing invisible lines. Blaschko made a chart of the lines and named them, well, obviously, Blaschko Lines.
Blaschko Lines follow the same pattern on all people. They run down the arms and legs and curve around the sides like tiger stripes. On the chest and upper back, they rise in a swirl before dipping down to meet in a deep “V” along the spine and the middle of the chest. They also run along the face above and below the eyes and over the ears, looking a little like painted-on glasses.
The amazing thing is, Blaschko Lines don’t correspond with any other system in the human body — they don’t follow the lines of nerves, arteries, veins, muscles, nor do they correspond with the endocrine system.
So what are these invisible lines on our bodies?
Most scientists think that it’s a remnant of the way the epidermal cells move during our embryo development. As the fetus grows, skin cells multiply rapidly forming groups along these lines. It could be that these different waves of development respond to stresses differently. When the skin is stressed by inherited or acquired skin problems, they move along these lines.
Sure, they are invisible for most of us, but for example, humans with chimerism can show them dramatically (google it at your own risk).
The lines can be observed in some animals, like cats and dogs, especially if they’re chimeras, too. They have different colored eyes and fur, so their owners usually name them Bowie, go figure.
Don’t envy zebra or a tiger no more, you striped animal, you.
Stats for nerds: