Posted in GENERAL_SCIENCE

What are the white half-moons on your fingernails?

Fingernails and Toenails made their way into mainstream fashion. They get polished with variety of colors, they get clipped, they get shaped into a subtle free curve. So what are those white half-moons on your fingernails? Aren’t you curious to know?

Basic Anatomy


Anatomy of nail @mayoclinic

Fingernails and toenails are made up of several layers of hardened cells. The nail plate (hard part) is less than 1mm thick and transparent, allowing the pink nail bed beneath, with its plentiful of blood supply, to show through.
Only the half moon-shaped area, known as lunula, at the bottom of each nail is white and opaque. This is where the nail root or matrix is located and it is here that new cells are produced continuously. These new cells push forwards, dying as they go, and the stored keratin inside causes them to harden and finally become transparent and thus forms nail plate.

Fingernails grow at a rate of about 1 mm a week, toenails more slowly. The little white half-moons vary in size, being larger on some people and smaller on others. Sometimes the lunulae can’t be seen at all because the matrix is hidden beneath the cuticle and the skin on the fingers.

What could an abnormal nail indicate?


  • A bluish discoloration of the lunula is a sign of a shortage of oxygen due to poor circulation, possibly caused by heart or vascular disease. This is called cyanosis.
  • People with chronic renal failure may produce more melanin which cause your nail bed to turn brown
  • In case of severe renal disease the white lunula may extend upto half the way up and other half turn brown. This is called half-and-half nail
  • Tetracycline medications are used to treat acne and skin infections.Long term use may turn lunulae yellow.
  • It is a myth that small white flecks seen sometimes indicate calcium deficiency.The small, white flecks that are sometimes seen on nails are merely the result of minor injuries and nothing to worry about.
  • Excessive fluoride ingestion may turn lunulae black.

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