Blaschko's Lines and Invisible Stripes on Human Skin

Blaschko's Lines Are Human Stripes Visible Under UV Light

Woman under black light
UV light reveals Blaschko's lines on skin.

Jane Khomi / Getty Images

Unless you have one of a number of skin diseases, you may not realize you have stripes, much like those on a tiger! Ordinarily, the stripes are invisible, though you can see them if you shine an ultraviolet or black light over your body.

Key Takeaways: Blaschko's Lines

  • Blaschko's lines or the lines of Blaschko are a series of stripes found on human and other animal skin.
  • The lines follow the path of embryonic skin cell migration.
  • Normally, the lines are not visible under ordinary light. However, they may be viewed under black or ultraviolet light. Several skin conditions follow the lines of Blaschko, making the path visible.

What Are Blaschko's Lines?

The Lines of Blaschko or Blaschko's lines make V-shaped stripes down your back, u-shapes on your chest and stomach, simple stripes on your arms and legs, and waves on your head. The stripes were first described by German Alfred Blaschko in 1901. Blaschko was a dermatologist who observed pigmented patterns in people with certain skin diseases. The patterns are also visible in people with chimerism. A chimera begins as two cells that have different DNA from each other. As these cells grow and divide, they contain slightly different instructions on how to produce proteins, including pigments.

The lines don't follow blood vessels, nerves, or lymphatic vessels, believed instead to reflect the migration of embryonic skin cells. Under ordinary conditions, skin cells are programmed to produce the same amount of pigment as each other, so the stripes aren't noticeable. The slight differences are more obvious under the higher energy of ultraviolet light. Other animals besides humans display Blaschko lines, including cats and dogs.

How to See Your Human Stripes

Whether or not you can view your own human stripes depends on your natural skin pigmentation and the type of UV light you use. Not all black lights are sufficiently energetic to make the lines visible. If you want to try to view your own stripes. you'll need a dark room and a mirror. Shine the black light over exposed skin and look for the pattern.

Inflammatory verrucous linear epidermal devus
Verrucous linear plaques follow Blaschko's lines. Littlekidsdoc / Creative Commons Attribution-Share Alike 4.0

Conditions Where Human Stripes Are Visible

Several skin disorders may follow Blaschko's lines, making them visible. These conditions may be inherited or acquired. Sometimes the stripes are visible throughout life. Under other conditions, they appear and then fade. While it's possible for the whole body to be affected, many times the lines only appear on a single limb or region. Here are some examples of skin conditions associated with Blaschko's lines. In some cases, the conditions trace Blaschko's lines as pigmentation, lack of it, or other discoloration. In other cases, the lines may be marked by inflammation, papules, abnormal hair, or scaly skin.

Congenital Skin Disorders

  • linear sebaceous naevus (lifelong)
  • unilateral naevoid telangiectasia (lifelong)

Acquired Skin Disorders

  • lichen striatus (one to two years)
  • linear psoriasis (one to two years)
  • linear scleroderma

Genetic Skin Disorders

  • Conradi-Hunermann syndrome
  • Menke’s syndrome

How Are Blaschko's Lines Treated?

If Blaschko's lines were simply stripes, treatment might be as simple as applying make-up or a drug to fade the pigment. Sometimes Blaschko's lines only affect skin pigmentation. However, the marks associated with skin conditions may present as dermatitis, with papules and vesicles. In some cases, corticosteroids may improve skin health. Treatments that reduce physical and emotional stress and address the underlying cause of the condition may also help.

Sources

  • Blaschko, Alfred (1901). Die Nervenverteilung in der Haut in ihre Beziehung zu den Erkrankungen der Haut [The distribution of nerves in the skin in their relation to diseases of the skin] (in German). Vienna, Austria & Leipzig, Germany: Wilhelm Braumüller.
  • Bolognia, J.L.; Orlow, S.J.; Glick, S.A. (1994). "Lines of Blaschko." Journal of the American Academy of Dermatology. 31 (2): 157–190. doi:10.1016/S0190-9622(94)70143-1
  • James, William; Berger, Timothy; Elston, Dirk (2005). Andrews Diseases of the Skin: Clinical Dermatology (10th ed.). Saunders. p. 765. ISBN 978-0-7216-2921-6.
  • Roach, Ewell S. (2004). Neurocutaneous Disorders. Cambridge University Press. ISBN 978-0-521-78153-4.
  • Ruggieri, Martino (2008). Neurocutaneous Disorders: Phakomatoses & Hamartoneoplastic Syndromes. Springer. p. 569. ISBN 978-3-211-21396-4.