One of our favorite daily pleasures is reading the post of the day from Today I Found Out. It’s a hodge-podge of esoteric information that never fails to entertain. Case in point – they recently addressed the question “Why don’t fingernails grow at the same rate.”
You should really check out the full answer, but here’s a quick recap. In case you never thought about it, the nails on your fingers and toes do grow at different rates. For fingers that rate is about 3.5 millimeters per month and for toenails it’s about 1.6 mm per month. No one knows for sure why this is true but there is a good theory that explains why nails grow at different rates. It involves the idea of “micro-trauma.”
Nail growth is determined to a large extent by blood supply. So, all other factors being equal, the nails that get the greatest supply of nutrients from the blood will grow the fastest? Interestingly, increased blood flow can be triggered by injury. (The body’s natural reaction is to send more blood and nutrients to damaged areas. Because your hands are constantly interacting with the environment your finger nails experience a greater degree of tapping and bumping than your toenails do (since they’re tucked away in your socks and shoes.) It’s thought that this constant barrage of “micro-trauma” is enough to trigger the body’s defense mechanism. So, more stress on the nail results in more blood flow which leads to more growth. Clever, huh?