Understanding the Nail

Your nails are made from the same protein that makes up your hair: keratin. Nails grow from a process called keratinization: cells multiplying in the base of each nail and then layering on top of each other and hardening.

How strong, thick, and fast your nails grow is hereditary. Unusual nail growth, such as toenails growing upward, could be hereditary as well.

Nail structure

Each toenail and fingernail has six structures:

  1. The nail matrix is the root of the nail. It grows out of a small pocket under your skin. The matrix is always making new cells that force the old ones to bunch up and get pushed through the skin. By the time you can see the nail, the cells there are dead.
  2. The nail plate is the visible part of the nail.
  3. The nail bed is under the nail plate.
  4. The lunula is part of the nail matrix. It’s the small, white crescent shape that you can sometimes see under your skin at the base of the nail plate.
  5. The nail folds are the skin grooves that hold the nail plate in place.
  6. The cuticle is the thin tissue over the base of the nail plate where it grows out of your finger.

Although nails will typically curl under if they grow long, a toenail that grows upward isn’t uncommon. This is called a vertical nail.

Toenails may curl upward for a number of reasons:

A toenail that grows upward could also have more complex medical explanations, such as:


Onychogryphosis is a thickening of the nails due to injury or infection. It mostly affects the toes — specifically the big toes. This condition is also known as ram’s horn nail and claw nail because it causes the nails to curve and resemble the shape of a ram’s horn or claw.

Nail-patella syndrome

Nail patella syndrome (NPS) is a genetic disorder that occurs in 1 in 50,000 people. Almost all people with NPS have nail abnormalities, and the fingernails are more likely to be affected than the toenails. People with NPS often have skeletal abnormalities involving the knees, elbows, and hips, and are prone to develop kidney disease.


This condition is characterized by thin and fragile nails that look concave or “scooped out,” similar to a spoon. Koilonychia typically affects fingernails. It can be hereditary or a sign of iron deficiency anemia, malnutrition, celiac disease, heart disease, hypothyroidism, or the liver condition hemochromatosis, in which your body absorbs too much iron from the food you eat.

If you feel that you might have onychogryphosis, NPS, or koilonychia, schedule an appointment with your doctor. The Healthline FindCare tool can provide options in your area if you don’t already have a doctor.

Whether or not you’re under a doctor’s supervision, it’s important to maintain your toenails. Upward-growing toenails tend to rip more often, exposing the area to infection, so careful hygiene is vital.

The most important thing you can do is trim your toenails using a strong, sharp nail clipper.

Cut each toenail to the point where it begins to curve upward. Cut the nail straight across without cutting the edges inward. It’s also important to leave the nail a little long to prevent it from growing inward. The goal is to have an even nail.

Try to avoid cutting nails when they are wet. Dry nails are less prone to cracking.

Here are some other tips for maintaining good foot and toenail hygiene:

  • Inspect your toenails at a minimum of once per week.
  • Use a nail cleaner to carefully remove any dirt under your nails.
  • Wash your feet in warm water and dry them thoroughly.
  • Moisturize your feet with a foot cream after washing them. Rub the cream over your nails and cuticles as well.
  • Ensure that your nails are smooth by filing them with an emery board. Among other benefits, this prevents them from catching on socks.
  • Wear thick socks to cushion against the friction between your toenails and your shoe. Natural fiber socks absorb sweat better than synthetic ones, allowing your feet to breathe.
  • Buy shoes that fit properly and have plenty of room for air movement.
  • Avoid harsh chemicals such as strong soaps and detergents.
  • In public places like gyms and swimming pools, don’t share towels, always dry yourself thoroughly, and never go barefoot. Always wear flip-flops, slides, or other appropriate footwear.

It’s possible to have toenails (and even fingernails) that grow upward. To prevent this issue from arising or getting worse, keep your feet clean and dry, and trim your nails frequently.

If your nails grow upward, you have depressed nail beds, or you notice any other issues, make an appointment to see your doctor.