Those lines and discolorations on your fingers and toes may be warning flags that you have an underlying medical condition – or simply a problem with the nails themselves. Take a closer look at your nails and watch out for the following symptoms.
By Diana Rodriguez
Medically reviewed by Lindsey Marcellin, MD, MPH
Toenail and fingernail disorders may signal problems that reach far beyond your fingers and toes. Nail abnormalities often indicate an underlying medical condition or a deficiency in certain vitamins and minerals. Warning signs to look out for include yellow nail discoloration, nail splitting, nail cracking, black fingernails, ridges on nails, and white spots on fingernails. So even if you skip regular manicures and pedicures, pay close attention to your nails and discuss any toenail or fingernail changes or disorders with your doctor.
Nail Splitting and Nail Cracking
Split nails or cracked nails can be problematic all on their own, but they can also be fingernail disorders that signal another health problem. Nail splitting and nail cracking can be due to a thyroid condition (hyperthyroidism or hypothyroidism) or psoriasis. If you find that your nails are brittle or split or crack easily and often, talk to your doctor about health conditions that may be responsible.
Soft or Brittle Nails
Fingernails that are soft to the touch or flake apart easily are commonly caused by a lack of the protein keratin. Keratin deficiency often results from crash dieting or some other sudden dietary changes. A protein-rich diet can reverse the damage, as can taking a daily supplement of biotin, a B vitamin. Other causes of soft or brittle nails include chemicals in products used as part of a manicure or pedicure (such as acetone and methyl acrylate), and health conditions, including Crohn’s disease and anemia.
When nails grow into the skin instead of straight, an ingrown nail occurs. This painful toenail and fingernail disorder is most often caused by an injury to the nail — someone steps on your foot or you stub your toe — or from wearing shoes that don’t fit properly. But nail disorders such as a nail fungus can also trigger an ingrown nail. Ask your doctor if you can attempt to treat an ingrown nail yourself; a severely ingrown nail may require antibiotics to prevent an infection or minor surgery to remove some or all of the ingrown nail.
Nail Fungus and Yellow Nails
Nails that crumble and break, turn yellow, or begin to smell may signal a fungal infection, also known as onychomycosis, which can affect fingers or toes. You may have picked up the toenail fungus in a public pool or locker room — any place that’s moist and warm. Have your nails inspected by a doctor who can confirm the diagnosis and recommend treatment, either with an anti-fungal cream or a course of oral antifungal medication. Frequent fungal infections may indicate a weakened immune system, a health problem like diabetes, or poor circulation. To prevent toenail fungus, keep your feet clean and dry, and wear shoes or sandals in public places.
Black Lines in Nails
A black line or streak that appears in a nail is often from some type of injury. But if you don’t remember accidentally whacking your index finger or stubbing your toe on a table leg, start looking elsewhere for an explanation. These black lines could be warning signs of melanoma, an extremely dangerous type of skin cancer, so you should see a doctor to have them checked out.
Blood Under Nails
You can accumulate blood under a nail when the nail has been injured — hit against something, crushed, pinched, or otherwise traumatized. The nail may look black due to the blood that pools beneath it, and the nail may eventually fall off. Sometimes, to alleviate pain and pressure, it’s necessary for a doctor to puncture a small hole in the nail to allow the blood to drain. Splinter-like streaks of red may be caused by an injury, but they could possibly indicate an infection of a heart valve, which showers the bloodstream with debris that causes the marks to appear. If you see streaks of red in your nails when you haven’t injured them, ask your doctor about it.
Ridges on Nails
Ridges on nails can be more than unsightly — they may indicate a nutritional deficiency. Ridges on nails can be a sign of malnourishment or a specific deficiency in iron, in which case you may also have depressed areas on the nail. Horizontal ridges on nails can also result from arsenic poisoning. See a doctor for evaluation if you notice ridges forming on your nails.
White Spots on Fingernails
White spots on fingernails are generally of no concern. They usually occur as a result of a minor injury to the nail that you may not even remember. Over time, they grow out and are clipped or filed off. But if you frequently see white spots on your fingernails and find that they don’t go away, you may have an infection that requires medical attention.