Have you ever taken off your nail polish only to notice a dark line on the nail running vertically down your finger? These black lines on fingernails may look like bruising or internal coloring — not like you just accidentally created an edgy nail-art trend. Since your nails are a reflection of your overall health, if you see any abnormal markings or they are extremely brittle and keep breaking, it’s important to get anything out of the ordinary checked out by a medical professional first to determine if it’s just a splinter hemorrhage, melanonychia, or something worse like melanoma.
To help us understand what those thin black lines on nails are and how to treat them, we turned to pros. Keep reading for everything you need to know.
Experts Featured in This Article
Joshua Zeichner, MD, is a board-certified dermatologist and director of cosmetic and clinical research in dermatology at Mount Sinai Hospital in New York City.
Hannah Lee is a celebrity manicurist.
Common Causes of Black Lines on Nails
- Splinter hemorrhage (nail trauma)
- Fungal infection
- Melanonychia
- Melanoma
Black Lines on Nails From Longitudinal Melanonychia
Not all marks on your nails are cause for alarm. “A black line that extends longitudinally from the cuticle to the free edge of the nail is often pigment,” board-certified dermatologist Joshua Zeichner says. “This may be a normal variant. Just like we develop moles on the body, they can develop at the base of the fingernail. When this happens, the extra pigment that is produced in the base of the nail travels with the nail as it grows out. This is known as longitudinal melanonychia. Especially in people with more melanated skin, these types of streaks are commonly seen in multiple nails.”
While this is fairly common and usually isn’t an indication of anything serious, “If it occurs in a single nail, and the streak is new, it should be evaluated,” says Dr. Zeichner. “The key sign to look for is whether the pigment affects the skin of the cuticle itself. When it does, it is worrisome.”
Black Lines on Nails From a Splinter Hemorrhage
“The most common dark streaks that occur in nails develop as a result of trauma,” says Dr. Zeichner. “Known as splinter hemorrhages, these are small black streaks that appear longitudinally in the nail. They develop when blood leaks into the space between the nail and the nail bed and gets trapped in the bridges of the skin. They are known as splinter hemorrhages because of their resemblance to a splinter since they have a long, thin shape.”
It can look black or reddish brown in color, doesn’t change appearance when you apply pressure to the nail, and appears in one or more places under your nail. “The good news is that these are completely harmless,” says Dr. Zeichner. “No treatment is necessary, as they grow out with the nail. They typically develop quickly, seemingly out of nowhere.” Note: thicker lines that create a horizontal stripe on the nail are called Beau’s lines, which are often symptoms of a more serious condition.
As Dr. Zeichner mentioned, splinter hemorrhages are often caused by trauma. “Another common reason these may appear is due to poor nutrition or a fungal infection,” says manicurist Hannah Lee.
Serious conditions that can cause a splinter hemorrhage include bacterial endocarditis, vasculitis, systemic diseases, diabetes, Raynaud’s disease, and cholesterol. Lee emphasizes the importance of seeing a pro if you think these may be the underlying cause: “It is always recommended to visit with your doctor to confirm why these lines are appearing,” says Lee. “From there, it’s best to discuss a plan on what you may be lacking or need to do to properly treat the lines with the guidance of a medical professional.”
How to Treat Black Lines on Nails
There is no real treatment for splinter hemorrhages, other than time. “You usually just wait for the black lines to grow out as long as it is not caused by something more serious, like melanoma,” Lee says. (Again, you’ll want to see your doctor to be sure.)
If the black lines are an eyesore and you’d rather not look at them every day, painting your nails can help cover them up until they go away. It’s fine to use colored polish, which can easily be removed at home if you need to check on your nail health. “It is totally fine to paint over them if it’s just caused by something like trauma,” Lee says. “If it turns out to be something like a fungal infection or melanoma, it would be best to get that treated immediately before applying polish again.”
Most of the time, thin, vertical black lines under your nails are no cause for concern. But if you’ve had them for a while or you just want to make sure they aren’t a sign of something more serious, getting examined by a medical professional is your best bet.
Jessica Harrington (she/her) is the senior editor of PS Beauty, where she oversees coverage around makeup, skin care, hair, tattoos, and more. With more than eight years of industry experience, she has interviewed countless celebrities, reported on hundreds of beauty trends, and swatched more lipsticks than she can count. Prior to PS, Jessica worked for publications such as Makeup.com, Skincare.com, and The Zoe Report.
Sydni Ellis is a former PS contributor.
#Black #Lines #Nails #Expert #Explains
