Nails (Fingernails, Toenails)

What are nails?

Nails are structures at the tips of your fingers and toes that protect delicate tissues beneath them. Healthy fingernails and toenails have a smooth texture and are strong enough to withstand the wear and tear of daily tasks. Your nails are part of your body’s outer layer, which healthcare providers call your integumentary system.

Why do we have fingernails and toenails?

Fingernails and toenails have several functions:

• Protecting the tips of your fingers and toes (which contain blood vessels and nerves)
• Enhancing your sense of touch
• Serving as a practical tool for daily tasks like scratching an itch or picking up tiny objects

The nails on our fingers and toes are a defining feature of primates. Other mammals have variations of nails, like claws or hooves.

What’s the anatomy of my fingernails and toenails?

You might think of your nail as just the hard surface that you trim, file or polish. But that’s only the visible part of what providers call your “nail unit.” There’s lots going on under the surface!

Each nail unit has several parts, including some you can’t see or feel. For example, even though you can’t see most of your nail matrix, it’s hard at work making special cells that become your shiny nail.

The table below lists the main parts of your nail. And in case you were wondering, the basic anatomy is the same for fingernails and toenails.

What are nails made of?

Your nails are made of specialized skin cells. That’s why they’re sometimes called “skin appendages." The hard part of your nail (nail plate) is made of:

• Keratin, which is a protein that keeps your nails healthy and strong (this is the main component of your nails)
• Water, which helps keep your nails from getting too dry or fragile
• Fats (lipids), which help water stay in your nails

Are fingernails bones?

No, fingernails aren’t bones. Keratin is the building block of your nails. Collagen, a different type of protein, is the building block of your bones.

How long does it take for fingernails to grow?

Fingernails typically grow about 3 millimeters per month. If you lose a fingernail, don’t worry, it can grow back. Full regrowth takes at least six months.

How fast do toenails grow?

Toenails usually grow about 1.5 millimeters per month. This means they grow more slowly than fingernails. Full regrowth takes 12 to 18 months. 

What conditions or disorders can affect my nails?

Injuries, infections, skin diseases and other conditions can affect the health of your nails. These issues typically make your nails look or feel different than expected. For example, your nails might break or crack easily. Lines or ridges may form on your nail’s surface. Your nail area might swell or hurt.

Some of these issues are systemic. That’s the medical term for when something affects your whole body or many parts of it. But some conditions mainly affect your nails. Providers call these nail disorders or nail diseases. Here are some examples:

• Brittle nails: Your fingernails become dry, fragile and prone to breaking. Causes include nutritional deficiencies, skin diseases (like eczema or lichen planus), medications and underlying medical conditions.
• Ingrown toenails: The hard part of your nail (nail plate) grows into the skin alongside it (lateral fold). It’s also possible for your nail plate to grow into the skin at the base of your nail (proximal fold). Providers call this retronychia.
• Nail cancer (subungual melanoma): This type of skin cancer affects one of your fingernails or toenails. A brown, black or red line across your nail is the most obvious symptom. This condition can be fatal and needs prompt treatment.
• Nail infection (paronychia): Bacteria enter broken skin around your nail plate, causing an infection. Anything that dries or causes breaks in your skin — from frequent dishwashing to nail biting — can raise your risk for a fingernail or toenail infection.
• Nail psoriasis: This type of psoriasis affects your nails — most commonly, your fingernails. It’s a chronic autoimmune condition.
• Nail separation (onycholysis): Your nail plate separates from the tissues underneath (nail bed). Fungal infections, medications and trauma from repeated manicures/pedicures are common causes.
• Toenail fungus (onychomycosis): Fungus can affect any of your nails, but it typically takes up residence in your toenails — especially your big toe. Going barefoot around pools and in public showers raises your risk of toenail fungus.

It’s also possible to injure your nail, causing pain and other symptoms. A subungual hematoma is a common example of a nail injury. This is when direct trauma to your nail — like slamming your finger in a door — causes blood to pool beneath your nail plate.

Signs or symptoms of nail disorders

Common signs and symptoms of nail disorders include:

• Changes to your nail color that look like patches, lines or spots
• Pits or ridges in your nail
• Flaking or peeling away of parts of your nail
• Pain or swelling of the skin around your nail

If you notice changes to any of your nails or the skin around them, contact a healthcare provider. Many nail conditions can be annoying or disruptive, but they’re not life-threatening. However, some conditions, like nail cancer, need a quick diagnosis and treatment. Your provider can identify the cause of your symptoms and recommend what to do next.

What are nail lines?

Nail lines are discolored streaks that appear on your fingernails or toenails. They commonly run from top to bottom (vertically or longitudinally). Some lines run from side to side (horizontally).

Nail lines have many possible causes — from minor injuries that heal on their own to serious medical conditions that need treatment. In general, nail lines can signal:

• A nail disorder or injury
• An underlying medical condition (an issue affecting other parts of your body, not just your nails)
• A vitamin or mineral deficiency
• A reaction to medication

The appearance of your nail lines helps your provider narrow down possible causes. Here are the main types of nail lines:

• White lines (leukonychia): Possible causes include fungal infections, repeated stress on your nails, heart failure, arsenic poisoning and drug side effects.
• Red lines (longitudinal erythronychia): When on just one nail, possible causes include noncancerous (benign) tumors or cancer. Underlying conditions like lichen planus or Darier disease (an inherited skin condition) typically cause streaks on multiple nails.
• Brown-black lines (longitudinal melanonychia): These are often harmless and commonly occur in people with darker skin as they get older. But they can also signal an infection, nail injury or cancer.

Beau’s lines aren’t discolored streaks, like the lines above. Rather, they’re ridges or grooves in your nail that run from side to side. They’re typically a sign that something — like stressor illness — has interrupted nail growth.

What are common treatments for nail disorders?

Possible treatments include:

• Topical medications (drops or creams) that prevent or fight infection, reduce inflammation or ease pain
• Oral medications, like acitretin for nail psoriasis or terbinafine for fungal infections
• Supplements, like certain vitamins or minerals, that strengthen nails
• Nail removal (nail avulsion), in which your provider may apply a chemical to your nail or do a minor surgery
• Treatment for other medical conditions, which can vary widely based on your diagnosis

How can I care for my nails?

There’s plenty you can do to keep your nails in good shape:

• Wear gloves to protect your nails when doing dishes or other chores.
• Cut your nails straight across with just a slight rounding at the tips. This lowers your risk of an ingrown nail.
• Don’t bite or pick at your nails.
• Give your nails regular breaks from polish. Avoid or limit gel polish.
• Wear comfy shoes that fit well and don’t squish your toes.
• Don’t go barefoot when walking alongside swimming pools or in public showers. Wear sandals or shoes to protect against foot and toe fungus.
• Use nail moisturizers, especially if you have brittle nails. Ingredients like petrolatum, lanoline, glycerin and propylene hydrate and protect your nails.
• Follow your provider’s guidance for nail care and treatment.

What’s the link between fingernails and health?

Your fingernails can show a lot about your health. For example, changes to your nail color or texture can be signs of:

• Heart failure
• Kidney failure
• Nutritional deficiencies
• Infection
• Heavy metal poisoning

These are just a few examples of what your nail appearance can reveal.

That’s why it’s important to see a provider if you notice any changes to your nails without a known cause. Your provider will figure out what’s going on and make sure you get the care you need.

What is a fingernail doctor called?

Dermatologists are specialists in your skin, nails and hair. But your primary care provider can also diagnose and treat many nail conditions.