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Dermatologist Shares "Nail Sign You Should Never Ignore" in New Video

It can be a lot worse than just stubbing your toe on a piece of furniture.

When you think about skin cancer, some things that may come to mind are unusual moles or freckles or patches of red and flaky, irritated skin—not your nail beds. That said, inspecting your nails for abnormalities is just as important as checking your arms, shoulders, and back. Lindsey Zubritsky, MD, a board-certified dermatologist living in Mississippi, is warning her 1.4 million TikTok followers about a malignant type of skin cancer in the nail that often goes undetected and is commonly misdiagnosed as bruised skin or trapped dried blood.

RELATED: These 3 Common Practices Are Horrible for Your Nails, Dermatologist Says.

For instance, if you've ever stubbed your finger in a car door or drawer or accidentally dropped a heavy object on your toe, you may have noticed a dark spot underneath your nail the following day. This is called a subungual hematoma, and it's a normal bodily response, Zubritsky said in the clip.

After a few weeks, the hematoma (which is basically a pool of dried blood) will eventually grow out and you'll be left with a healthy new nail. However, there are other kinds of dark streaks on the nail you should look out for, Zubritsky cautioned.

"If you have a dark-pigmented vertical streak going down your nail, this absolutely should be checked," said Zubritsky. "It could potentially be a very serious form of skin cancer called a subungual melanoma."

"This is the one nail sign I am begging you as a dermatologist not to ignore," continued Zubritsky, adding that it "can be easily missed if you don't know what you're looking for."

Though rare, subungual melanoma can turn serious if left ignored. According to Cleveland Clinic, the nail cancer occurs in the nail matrix, which is connected to nerves, blood vessels, and lymphatic tissue. Unlike more common forms of skin cancer, subungual melanoma isn't surface level; instead, it takes root in the melanocytes cells.

"Subungual melanoma usually has a distinct shape. Some may describe it as looking like you drew a line on your nail with a black or brown marker," explains Cleveland Clinic. "It appears as a dark line on your nail and runs from bottom to top. This streak or stripe may start small but grow to cover the entire nail and extend to the cuticle (skin part of your nail). The discoloration can be irregular and be varying shades of blackish brown."


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With how often our hands are in direct sunlight, you may be surprised to hear that subungual melanoma isn't caused by sun exposure.

The cancer, which is often found in the big toe, thumb, or index finger, may also cause split or cracked nail beds, irregular pigment, swelling, and cuticle discoloration.

"The really concerning sign is when you have discoloration or pigmentation that's starting to creep up into the skin," per Zubritsky.

However, not all dark lines on the nail are dangerous, she added. "Many people might have a benign streak on their nail called longitudinal melanonychia, which is totally normal," she explained. Longitudinal melanonychia is lighter in color, may be visible on multiple nails, and stable (aka, not progressing).

In fact, you're more likely to have the benign streak. Cleveland Clinic reports that subungual melanoma only accounts for 0.7 to 3.5 percent of all types of melanoma worldwide.

Either way, if you notice a new dark streak on your nail, or any skin abnormality for that matter, it's important to consult your dermatologist.

Best Life offers the most up-to-date information from top experts, new research, and health agencies, but our content is not meant to be a substitute for professional guidance. When it comes to the medication you're taking or any other health questions you have, always consult your healthcare provider directly.

Emily Weaver
Emily is a NYC-based freelance entertainment and lifestyle writer — though, she’ll never pass up the opportunity to talk about women’s health and sports (she thrives during the Olympics). Read more
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