1. Your nails are made of

Keratin is a type of protein that forms the cells that make up and other parts of your body.

Keratin plays an important role in nail health. It protects nails from damage by making them strong and resilient.

2. Yes, that’s the same stuff that makes up your hair

Keratin of your hair and skin, too. It also forms cells that are a key part of many glands and that line internal organs.

3. Your visible nails are dead

Nails start growing under your skin. As new cells grow, they push old ones through your skin. The part you can see consists of . That’s why it doesn’t hurt to cut your nails.

4. But they need blood flow to grow out and create the “nail”

Tiny blood vessels, called capillaries, sit under the nail bed. Blood flowing through the capillaries helps nails grow and gives them their .

5. Nails do have feeling — sort of

The nails you can see are dead and have no feeling. However, a layer of skin under the nails, called the dermis, has . These send a signal to your brain when pressure is applied to your nails.

6. Fingernails grow about each month

And toenails grow about per month. Those are the averages for healthy adults. Whether you’re getting proper nutrition and how well you take care of your nails can affect the growth rate.

7. Your nails stop growing when you die, though

Although the myth about nails growing after death , there’s a reason it exists. After someone dies, their skin dehydrates and shrinks, making it look like their nails grew.

8. Men’s nails

Their than women’s, too. The one exception is , when a woman’s nails and hair might grow faster than a man’s.

9. So do the fingernails on your dominant hand

If you’re right-handed, you might’ve noticed the nails on that hand than on your left and vice versa. This could be because that hand is more active (see item 11).

10. Seasons influence growth

Nails grow than in winter. Not much research has been done about why this happens, but one study involving rats found that cold weather .

11. How much you use your hands affects growth, too

Using your hands a lot makes your nails more prone to minor trauma from things like tapping them on a table or using a keyboard. This promotes blood circulation in your hands, .

12. Your nail color can change according to your health

About of all dermatological conditions are nail-related. Yellow, brown, or green nails usually mean you have a . In some cases, yellow nails are a symptom of a thyroid conditionpsoriasis, or diabetes.

13. White spots on your nails aren’t actually a sign of calcium deficiency, though

White spots or lines are usually caused by , like from biting them. These spots are typically harmless and will grow out.

14. And stress can really affect your nails

Stress can cause your nails to grow more slowly or even temporarily . When they start growing again, you might have . They’re usually harmless and will grow out.

15. Nail biting is the “nervous habit”

Also called , nail biting usually doesn’t cause long-term damage. However, it raises your risk of getting sick by spreading germs to your mouth. Damage to the skin around your nails could cause infection, too.

16. You really do need to let your nails “breathe”

To keep nails healthy, from using polish or having artificial nails. Using and removing these products can be hard on your nails, so taking a break from them helps nails repair themselves.

17. You can blame your parents for how thick (or thin) your nails are

Nail growth and other nail characteristics partly depend on your inherited genes. Other factors include your .

18. Cuticles do have a purpose

This small sliver of skin at the base of your nail protects the new nail from germs as it grows through your skin. You shouldn’t cut your cuticles. Doing so removes the important barrier that .

19. Nails separate primates from other mammals

Primates, including humans, have as well as opposable thumbs. This gives humans more agile hands that allow us to grasp things better than other mammals.

The bottom line

Your nails give you a picture of your overall health. Changes in your nail color or a disruption in their growth could be symptoms of a medical condition, poor nutrition, or excessive stress. Talk to your doctor if you’re worried about recent changes to your nails.

Follow for good nail hygiene:

  • Trim your nails regularly, keeping them short.
  • If you do have longer nails, scrub the underside of them when you wash your hands. Use soap and water every time and consider using a nail brush as well.
  • Sanitize nail grooming tools before each use (and make sure any salon you visit does the same).
  • Don’t bite or chew your nails.
  • Avoid ripping or biting off hangnails. Instead, use a sanitized nail trimmer to remove them.