A nail is a hard, slightly curved plate of protein that grows from the tips of your fingers and toes. It’s made almost entirely of keratin, the same tough structural protein found in hair, hooves, and horns. Nails serve as protective shields for the sensitive skin at the ends of your digits, and they act as rigid backboards that sharpen your sense of touch by giving your fingertips something to press against.
What Nails Are Made Of
The nail plate, the part you can see, is composed of about 80% hard keratin and 20% soft keratin. Hard keratin is the denser, more rigid type found in animal horns and hooves. Soft keratin is the same kind that makes up the outer layer of your skin. This blend gives nails their unique combination of strength and slight flexibility.
Keratin is rich in sulfur, which creates strong chemical bonds between protein fibers and gives nails their rigidity. Compared to skin, nails contain almost no fat (less than 1%, versus about 10% in skin) and far less water (7 to 12%, versus 20 to 40% in skin). That low moisture and fat content is what makes nails so much harder and more durable than the skin around them. Under a microscope, a nail plate is built from roughly 196 rows of tightly packed, flattened cells stacked on top of one another, forming a dense, layered shield about 0.4 to 0.5 millimeters thick.
Parts of the Nail
What you see when you look at your fingernail is only part of the story. The full nail unit includes several structures, some hidden beneath the skin.
- Nail plate: The hard, visible surface you trim and paint. It has subtle ridges running from base to tip. The white tip that extends past your fingertip is the free edge.
- Nail matrix: The tissue that actually produces the nail plate. It sits mostly hidden under the skin at the base of the nail. The small, pale half-moon visible at the base of your thumbnail (and sometimes other nails) is called the lunula, and it’s the only part of the matrix you can see.
- Nail bed: The skin directly beneath the nail plate. It’s rich in blood vessels, which is why healthy nails look pink.
- Cuticle: The thin strip of skin that seals the gap between the nail plate and the surrounding skin, keeping out bacteria and moisture.
How Nails Grow
Nails grow from the matrix outward, pushing new cells forward as older cells harden and flatten into the nail plate. Fingernails grow at an average rate of about 3.5 millimeters per month, or roughly a tenth of a millimeter per day. Toenails are significantly slower, averaging about 1.6 millimeters per month. At that pace, it takes a fingernail around three to six months to fully regrow from base to tip, while a toenail can take a year or longer.
Growth rate slows with age. One doctor who tracked his own thumbnail growth over decades found it grew at 0.123 mm per day at age 23 but had dropped to 0.095 mm per day by age 67. Younger people, and people whose dominant hand gets more blood flow, tend to have slightly faster-growing nails.
Why You Have Nails
Nails aren’t just cosmetic. They protect the tips of your fingers and toes from injury, acting as a hard cover over some of the most nerve-dense skin on your body. They also play a surprisingly important role in touch. The rigid nail plate creates a counter-pressure surface: when you press your fingertip against something, the nail pushes back against the soft tissue underneath, amplifying the signal your nerves send to your brain. Without nails, your fingertips would be less sensitive and far more vulnerable to cuts and crushing injuries. On a practical level, nails also help you grip small objects, scratch, and peel.
What Your Nails Can Tell You About Your Health
Changes in nail color, shape, or texture sometimes reflect what’s happening inside your body. Healthy nails are smooth, uniformly colored, and free of spots or discoloration. A few common changes worth paying attention to:
Pitting. Small dents or depressions in the nail surface are common in people with psoriasis or eczema. They can also appear with alopecia areata, an autoimmune condition that causes hair loss.
Clubbing. When nails curve downward and the fingertips look swollen or bulging, it can signal low blood oxygen levels, lung disease, heart problems, or liver cirrhosis. This change develops gradually and is worth having evaluated.
Terry’s nails. Nails that appear mostly white with a narrow band of pink or brown at the tip sometimes develop with aging, but they can also indicate liver disease, congestive heart failure, or diabetes.
Vertical ridges running from base to tip are normal and tend to become more pronounced with age. Horizontal ridges or grooves, on the other hand, can signal a period of illness, severe stress, or nutritional deficiency that temporarily disrupted nail growth.
Basic Nail Care
Keeping nails healthy doesn’t require much. Cut them straight across with sharp scissors or clippers, then round the tips slightly for strength. Trimming toenails regularly reduces the risk of trauma and ingrown nails. Avoid biting your nails or pushing back and cutting the cuticle, as the cuticle forms a seal that protects against infection. If you develop an ingrown toenail that’s painful or looks infected, resist the urge to dig it out yourself.
Because nails are naturally low in moisture, frequent exposure to water, harsh soaps, and chemical cleaners can dry them out and make them brittle. Wearing gloves during cleaning and applying moisturizer to your hands and nails can help maintain flexibility and prevent cracking.