Have you noticed a change to any of your nails lately? A change in color, texture, or shape can be harmless, but it can also be a sign of disease. If you notice any of the following changes to a fingernail or toenail, it’s time to see a board-certified dermatologist.

Medical name: Acral lentiginous melanoma

Dark streak

If a fingernail or toenail has a new or changing dark streak, it’s time to see a dermatologist for a skin cancer check. That dark streak could be melanoma, the most serious type of skin cancer.

Not every dark streak is a melanoma, but it’s always good to have a dermatologist examine one. Caught early and treated, that may be the only treatment you need.

Allowed to grow, treatment becomes more difficult.

Medical name: Onycholysis

Nail lifting up

If a nail starts to lift up so that it’s no longer completely attached, you’ll likely see white discoloration, as shown here. When a nail lifts up, the cause is often:

A fungal infection

Psoriasis

Injury from an aggressive manicure

Injury form cleaning under your nails with a sharp object

A dermatologist should examine any nail that’s lifting up. You may need treatment to clear an infection. A dermatologist can also give you some tips that may help the new nail grow out normally.

Medical name: Paronychia

Redness and swelling around a nail

If you have redness and swelling around a nail, you may have an infection. When diagnosed early, you can often treat an infection with soaks and antibiotics. If an open sore forms, you’ll need more extensive treatment.

Medical name: Paronychia

Greenish black color

When bacteria cause a nail infection, the nail can turn greenish black as shown here.

Without treatment, a nail infection tends to worsen. Treatment can get rid of your pain and tenderness and help clear the infection.

Medical name: Pitting

Pitted nails

If you have dents in your nails that look like they were made by an icepick, this could be a sign that you have a disease that affects your entire body.

People who have pits in their nails may have

Psoriasis

Atopic dermatitis

Alopecia areata

Seeing a board-certified dermatologist for a diagnosis is important. Dermatologists are the specialists who diagnose and treat these diseases. Treatment can help you feel more comfortable and prevent the disease from worsening.

Medical name: Yellow nail syndrome

Yellow nails

Wearing red nail polish without a base coat or smoking can turn your nails yellow. If your nails turn yellow, thicken, and seem to stop growing, it could be a sign of something going on inside your body.

Lung disease and rheumatoid arthritis can cause yellow nails. You may also have a serious nail infection, which requires treatment

Medical name: Beau lines

Deep grooves (or gaps)

Lines that run the length of a nail are common and usually nothing to worry about. If you see deep grooves that run the width of your nail like the ones shown in this picture, it means that something slowed (or stopped) your nails from growing for a while.

When something causes your nail(s) to completely stop growing for a while, you may see a gap. If this happens, you’ll have a place on your nail(s) that’s missing nail. The medical name for this condition is onychomadesis (on-ah-coe-ma-dee-sis).

A fever, injury, chemotherapy, or major stress can cause your nails to grow slowly or stop growing.

If you cannot think of what could may have caused your nails to grow slowly or stop growing, see your dermatologist or primary care doctor. Once you find and get rid of the cause, nails often start growing normally.

Medical name: Onychogryphosis

Ram’s horn nails

This happens when the nails thicken and overgrow. Some people get Ram’s horns because the condition runs in the family.

If you have a disease, such as psoriasis, ichthyosis, or circulation problems, you may also develop Ram’s horn nails.

Cutting and treating these nails requires help from a podiatrist or dermatologist.

Medical name: Koilonychia

Thin, spoon-shaped nails

If you have thin fingernails that dip down in the middle and look like spoons, you may not be getting enough iron. People develop an iron deficiency for many reasons, including:

Lack of proper nutrition

A health problem with their stomach or intestines

Sensitivity to gluten (celiac disease)

High altitude

Getting a proper diagnosis and treatment can help you feel better.

Medical name: Onychotillomania

Washboard nails

If you have grooves and ridges in the center of your thumb that look like the ones shown in this picture, you may have developed a habit of picking at (or pushing back) the cuticles on your thumbnails. Many people are unaware that they do this.

A dermatologist may be able to help you break the habit, allowing healthy nails to grow out.

Medical name: Clubbing

Curved nails

The curving can begin so gradually that many people are unaware it''s happening. As the nails continue to curve downward, fingertips often swell and the nails start to feel spongy when pressed on.

If you notice your fingernails start to curve, it’s time to see a board-certified dermatologist. Curved nails can be a harmless trait, which runs in the family. Curved nails can also be a sign that you have a disease in the:

Lungs

Heart

Liver

Stomach or intestine

Color change

A disease inside your body can cause your nails to change color. Certain color changes can be a warning sign of a specific disease, as the following table shows.

Color, Disease or other health problem

Blue nails, Not enough oxygen in your bloodstream

White nails, Liver disease, diabetes

Pale nails, Anemia

Half pink, half white nails, Kidney disease

Yellow nails, Lung disease, nail infection

Dusky red half-moons, Could be lupus, heart disease, alopecia areata, arthritis, dermatomyositis

Blue half-moons, Could be sign of poisoning