Growth starts beneath the cuticle
A fingernail is made by the nail matrix, a strip of living tissue tucked under the skin at the base of the nail. Matrix cells multiply, fill with tough keratin, and are pushed forward; the visible nail is made of these hardened cells. A change in growth therefore has to begin in the living tissue, not in the nail plate itself.
Why daily use might matter
Frequent movement and contact can alter circulation in the fingers. Blood brings oxygen and nutrients to the matrix, so differences in the conditions around the fingertips may help explain why nails on a dominant hand can grow a little faster. The effect is gradual: each nail advances only a small distance over time, making a side-to-side comparison more revealing than watching one nail day by day.
Use is not a precise growth switch, though. Nail growth also varies from finger to finger and with factors such as age, health, and the season. The practical result is a subtle asymmetry, not a dependable way to predict exactly how quickly any one nail will grow.
