Black Lines in Your Fingernails—Splinter Hemorrhages or Melanoma?

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black lines fingernailsHave you ever looked down at your hand and discovered black lines in your fingernails? What about your toenails? It can be pretty weird and unsettling, and it can also be the result of some bigger health problems. When red or black lines in the fingernails are vertical in shape, it could be a sign of melanoma or heart disease, so getting it checked out by the doctor is highly recommended.

What Are These Black and Red Lines in My Fingernails?

Not every black or red line running vertically down your fingernail or toenail is a cause for worry. Sometimes it can be related to a nutritional deficiency or an injury, and other times it can be benign. But sometimes it means cancer.

What kind of cancer is represented by black lines in the fingernails? Melanoma; specifically, a type called longitudinal melanonychia. This occurs when there is an overproduction of melanocytes, which are mature melanin-forming cells, in the area of the nail. Sometimes called “nail moles,” these black marks are similar to moles that can appear on other parts of the body (such as your arms, shoulders, face or back), and many times they are not malignant, but all the same they should be checked out by a dermatologist.
Black lines may not always be directly related to mole growth or melanoma, but could also be caused by aging, nutritional issues, arthritis, fungus infections, or a heart infection. Red lines that may develop under your nails are also an indicator that something could be wrong. These red lines, called splinter hemorrhages, can be the result of a heart infection that have caused capillaries to burst. We’ll take a closer look at these later.

Are the Black Lines in Your Fingernails Cancer?

Upwards of 75% of the time, these black lines occur on your thumbnail or big toenail, and the severity and prevalence will differ on who you are and your age. Dark-skinned people, for example, are far more likely to see black lines forming under their nails, but they also have more instances where said lines are benign. On the other hand, such lines are far less common in Caucasians, but when they do appear there’s a better chance that it’s melanoma. It should be noted that this type of melanoma, subungual melanoma, is extremely rare, especially in the United States.

When melanoma is responsible for the appearance of the lines, your doctor will consider a few things, such as:

  • Age: It’s much more common in those 50 to 70.
  • Width of the line: If the line is wider than three millimeters, it may be a cause for concern.
  • Pigment change: If the look of the pigment band at the top of the nail is discolored, it could be an indication that the lines are malignant melanoma.
  • Where it’s located: The thumb and big toe are the most common locations, followed by the index finger.
  • The coverage area: If the discoloration extends into the cuticle or nail fold, it could be cancerous. This means that your body is continuing to produce more of whatever’s causing the discoloration.
  • Family history: If someone else in your family has been diagnosed with melanoma, it could increase the chances you have it.

If you experience any of these symptoms, it’s recommended that you get to your doctor for an examination. There really isn’t much you can do on your own at this point, so it’s important to seek proper medical attention.

black lines in fingernails

When Black Lines in the Fingernails and Toenails Aren’t Cancerous

Of course, the black lines in your nails may not be melanoma. As mentioned, they are common in dark-skinned individuals, often without health repercussions. Still, it’s a good idea to show them to your doctor regardless of complexion and age.

As mentioned earlier, a fungus could cause the appearance of these lines, or it could simply be a result of aging. It could also have something to do with nerve damage resulting from a chronic condition like arthritis. Sometimes it could even be linked to a nutritional imbalance or deficiency.

When it’s a result of nutritional imbalances, then low blood levels of zinc, iron, calcium, or biotin could be the culprits. High levels of selenium may also play a role in forming black lines under the fingernails, so paying attention to diet and supplementation could offer some help. As always, it’s recommended to eat a balanced diet packed with nutrients. When your diet is made up primarily of vegetables, fruit, healthy fats, animal protein, and whole grains, you’ll be getting adequate amounts of all the nutrients you need. Taking a daily multivitamin to fill in the gaps can be a good idea, but it shouldn’t be used as your primary source of nutrition.

Are the Black Lines in Your Fingernails Heart Disease?

Black lines can signify some further health troubles, but so can reddish or brown ones. These lines, mentioned earlier, are called splinter hemorrhages and indicate small areas of bleeding beneath the nails. These thin red lines run vertically down the nail, and basically look like splinters, from which they draw their name. These can occur for a number of reasons, and sometimes it can be an indicator of heart disease or cardiovascular problems.

Splinter hemorrhages may be caused by small blood clots that damage the small capillaries beneath the nail. They can also occur as a result of:

  • An infection to the heart valve (also called endocarditis);
  • Vessel damage from swollen blood vessels (vasculitis); and
  • A bacterial infection resulting from an injury to the area.

Damaged blood vessels can be caused from a variety of factors and they can appear in other areas of the body, as well. The eyes and nose are other places where this is seen, and can be a result of stress or heart troubles. To combat this from occurring, it might be worthwhile to explore some lifestyle changes including more exercise, an improved diet, limiting stress, quitting smoking, limiting drinking, and trying to find ways to get better sleep.

black lines in fingernails

Black Lines in the Nails during Pregnancy

Pregnant women may also notice black lines or spots under their nails, or on other areas of the body. This is really nothing to worry about and should subside shortly after the pregnancy has concluded. Pregnancy prompts all kinds of hormonal changes, one of which can be accelerated melanin production.

Beyond Cosmetics: You Can’t Just Cover Up Black Lines in Your Fingernails

If you notice tiny black lines in your fingernails, there may be something severe causing it, with the worst-case scenarios being cancer in the form of melanoma or heart disease. If you notice these lines forming, please, don’t ignore them and go see your doctor as soon as you can.

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Dr. Victor Marchione, MD

About the Author, Browse Victor's Articles

Victor Marchione, MD received his Bachelor of Science Degree in 1973 and his Medical Degree from the University of Messina in 1981. He has been licensed and practicing medicine in New York and New Jersey for over 20 years. Dr. Marchione is a respected leader in the field of smoking cessation and pulmonary medicine. He has been featured on ABC News and World Report, CBS Evening News and the NBC Today Show and is the editor of the popular The... Read Full Bio »