Why Do Nails Grow?
Nails grow because living cells in the nail matrix (beneath the cuticle) continuously divide and produce keratin, a hard protein. As new cells form, they push older cells outward, which harden and die to form the visible nail plate. Fingernails grow about 3.5mm per month; toenails about 1.6mm. Growth is affected by age, health, nutrition, and season (faster in summer).
Key Takeaways
- The nail matrix, located beneath the cuticle, contains stem cells that constantly divide.
- Biting or trimming nails doesn't make them grow faster - this is a myth.
- White spots on nails are usually minor trauma to the matrix, not calcium deficiency.
Explanation
The nail matrix, located beneath the cuticle, contains stem cells that constantly divide. These cells produce keratin, the same protein in hair and skin. As new cells form, they flatten and harden while being pushed forward by newer cells behind them. The visible nail is made of dead, keratinized cells.
Fingernails grow faster than toenails because fingers have better blood circulation (being closer to the heart) and experience more frequent minor trauma that stimulates growth. The middle finger typically grows fastest. Nails on your dominant hand grow slightly faster due to increased blood flow from use.
Various factors affect nail growth rate: age (growth slows after 25), pregnancy (faster growth), malnutrition (slower), illness (can cause ridges or stop growth temporarily), and hormones. Nails grow faster in warm weather due to increased blood circulation, and grow at different rates in different fingers.
Nail composition reveals a lot about overall health. Nails are made of 80% hard alpha-keratin and contain trace amounts of calcium, iron, zinc, and sulfur. Deficiencies often show visible signs: iron deficiency can produce spoon-shaped nails (koilonychia), zinc deficiency causes white spots or lines, and B12 deficiency may turn nails dark or create longitudinal ridges. Endocrinologists and dermatologists sometimes examine nails as part of diagnostic assessments because changes can appear months before other symptoms.
The nail plate itself is dead tissue, but the nail bed underneath is richly supplied with blood vessels and nerves, which is why injuries under the nail are extremely painful. A subungual hematoma (blood under the nail from trauma) creates pressure that can cause throbbing pain for days. The growth rate difference between fingers and toes relates to blood supply: fingertip capillaries receive blood from the radial and ulnar arteries with a shorter travel distance from the heart, while toenails depend on blood traveling all the way to the feet through the posterior tibial and dorsalis pedis arteries.
Things to Know
- Biting or trimming nails doesn't make them grow faster - this is a myth.
- White spots on nails are usually minor trauma to the matrix, not calcium deficiency.
- Severe illness can cause a horizontal groove (Beau's line) as growth temporarily stops.
- Complete nail regrowth (if fully removed) takes about 6 months for fingernails, 12-18 months for toenails.