You have access to important clues about your health right at the tips of your fingers.
"A lot of times we'll learn in training that the nails can be a window into your health because they can sometimes be an indicator of some underlying medical problems," noted NBC News medical contributor Dr. Natalie Azar.
“Lots of things can be detected in the nail,” said Dr. Phoebe Rich, director of the Nail Disorder Clinic at Oregon Health and Sciences University and a dermatologist at the Oregon Dermatology and Research Center.
Here are seven nail symptoms and what to do next:
1. Symptom: Brown vertical stripe on the nail
This may be a sign of melanoma. While you may think the deadliest type of skin cancer always shows up as a mole or dark spot, it can actually start in the nail.
Only about 1 percent of all melanomas in Caucasians occur in the nail, but if you’re African-American, 20 percent of melanomas start there, Rich said.
“In more advanced cases, it can spread on to the cuticle area or the skin around the nail. That’s an ominous sign — it’s means it’s growing and spreading,” she noted.
Hormones and certain medications can also make pigmented bands in the nails, but be especially watchful for a brown or dark stripe that goes from the cuticle out to the free edge of the nail, especially one that’s getting wider.
Course of action: Get any brown pigmentation on your nail checked out by a dermatologist.
2. Symptom: Brittle nails
This common problem can happen because of an issue with your diet or the chemicals your hands are exposed to.
Nails are formed in the nail matrix, the root of the nail. If you are malnourished or lack certain nutrients, your body doesn’t have the material to make good nails, Rich said. That's why people with eating disorders can notice problems with nails. Brittle nails can also indicate iron-deficiency anemia or thyroid diseases.
Remember: Nails are made of keratin, a protein. A common myth is that calcium plays a role.
“I see this all the time. People come in and say, ‘I’m taking a lot of calcium so my nails should be strong,’” Rich noted. “Calcium makes bones strong, but doesn’t have anything to do with making nails strong.”
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If your body has the material to create the perfect nails, harsh chemicals can still break them down as they grow. Think of nails as a brick wall: the chemicals can remove the mortar that holds the bricks together, Rich said. That can include detergent water and nail polish remover.
Course of action: Make sure you are eating a well-balanced diet that includes plenty of protein.
Avoid using harsh chemicals on your nails. Even acetone-free polish remover can make your nails brittle if you use it too often and too much, Rich said.
3. Symptom: Ridges on nails
Vertical ridges are common as you get older and most people eventually get them.
“They’re kind of like wrinkles in the nail,” Rich said. She discourages patients from buffing or filing the ridges smooth because that thins the nail.
Deep horizontal ridges or depressions, known as Beau’s lines, are more alarming. They indicate something caused the nail to stop growing temporarily. Triggers can include high fever, chemotherapy, a serious illness, major surgery, blood transfusion, a car accident or any major stress to your system, Rich noted. You can have a series of parallel Beau’s lines if you experienced multiple episodes of stress.
Course of action: If you can’t link your deep horizontal ridges to a specific episode in your life, ask your doctor what the cause could be.
Vertical ridges are usually just a part of aging. If you want to cover them up, don’t buff, but use a ridge filler.
4. Symptom: Small white spots on nails
Many people think the spots are related to a vitamin deficiency, but that’s a myth, Rich said. The condition, called punctate leukonychia, is actually due to some kind of minor trauma when the nail is being formed.
Course of action: Wait — the spots will vanish as the nails grow out. You'll see them for a while because it takes about six months to grow a new fingernail from start to finish.
5. Symptom: Yellow nails
Very yellow nails that are thick and slow growing may be associated with lung problems, Rich noted. If you have yellow nail syndrome, you may also experience excessively curved nails and see them separate from the nail bed.
Course of action: See your doctor.
6. Symptom: Series of horizontal depressions on the thumb
That’s a classic sign of a habit tic deformity, where people chronically rub or pick the cuticle of the thumb with their index finger as the nail is being formed. It creates a washboard-like series of horizontal depressions on the thumb nail.
“A lot of people do it when they don’t know they’re doing it,” Rich said. “We see it a lot.”
Course of action: People can fix the issue if they simply stop manipulating their thumb cuticles, Rich noted.
7. Symptom: Infected, inflamed skin around the nail
This is known as paronychia and can be caused by pushing back the cuticle.
“Cuticles are really important and probably shouldn’t be pushed back,” Rich noted. “They seal the skin to the nail and keep stuff out.”
The cuticle prevents bacteria, fungus, yeast and mold from getting underneath your nail and causing an infection.
Course of action: Soak your nail in hot water two or three times a day to help reduce the swelling and pain, experts note. Your doctor may prescribe oral antibiotics or other medicine.
To prevent an infection, don’t use any sharp implements to cut or push back your cuticles, and don’t allow your manicurist to cut them, Rich advised. The best way to manage cuticles is to gently rub a towel over your nails after a shower when your skin is soft to get rid of the dead skin on the surface of the nail, she noted.
Nail discoloration or thickening can signal systemic health problems. Check with your doctor if you spot any changes.