· Melanonychia, a black line on your nail, can be a sign of melanoma or benign pigmentation changes. Injuries, medications, and conditions like hyperthyroidism may also cause dark lines on your... Having a dark line on your fingernails or toenails is called melanonychia. The lines are brown or black and usually look like a stripe that begins at the bottom of your nail bed and continues to the top. Melanonychia may appear in one nail or several. These lines can occur naturally if you have a dark complexion. See full list on healthline.comThere are two broad types of melanonychia:•Melanocytic activation: This is an increase in the production and deposits of melanin in your nail but not an increase in pigment cells. Causes include trauma, nutritional deficiency, and medication.See full list on healthline.comMelanonychia can appear in fingernails or toenails. It can also occur in more than one nail.It may look like:•a black or brown vertical stripe down the length of the nail•a black or brown discoloration stripe spread across the nailSee full list on healthline.comThe nails of your toes or fingers are usually translucent and nonpigmented. Melanonychia occurs when the pigment cells, called melanocytes, deposit melanin — brown-colored pigment — into the nail. These deposits are usually grouped together. As your nail grows, a stripe of brown or black appears. Melanin deposits are caused by two primary processes, which have different causes.Causes of melanocytic activation can include:•pregnancy•racial variations•traumaSee full list on healthline.comA diagnosis of melanonychia is reached after a series of exams. A healthcare professional may also review your medical history for conditions that might cause melanonychia.They will likely examine your fingernails and toenails. This includes looking at:•whether your nail has a structural irregularity•how many nails have melanonychia•the color, shape, and size of your melanonychiaA doctor may do a dermatoscopic exam using a specific type of microscope to closely examine the discolored areas. They typically look for signs that your melanonychia may be malignant. See full list on healthline.comThe treatment for melanonychia depends on the cause. If your melanonychia is noncancerous, you often do not need treatment.If your melanonychia is caused by medication, a doctor may change your medication or have you stop taking it for a time, if possible. For medications that you cannot stop, melanonychia may be a side effect that you will get used to. Other treatment options depend on the cause and may include:•taking antibiotic or antifungal medications if infection is the cause•treating the disease or medical condition causing the melanonychiaIf your melanonychia is malignant or cancerous, the tumor or cancerous area must be removed. That may mean you’ll lose all or part of your nail. In some cases, the finger or toe that has the tumor may need to be amputated.See full list on healthline.comPossible complications of melanonychia include:•nail cancer•bleeding under the nail•splitting of your nail•structural irregularity of your nailThe nail biopsy can also cause a structural irregularity because it removes a portion of the nail.See full list on healthline.comWhat does a dark line on your nail mean?A dark line on your nail can result from nail injury, infection, or cancer, among other causes. A doctor can perform exams to determine whether melanonychia is malignant.What causes dark stripes on nails?Dark stripes on nails typically appear due to increased deposits of melanin, which gives skin its color. Melanonychia can develop due to many causes, including nail cancer, trauma, and other health conditions.What deficiency causes black lines on nails?Deficiencies in vitamin B12, vitamin D, and protein can cause dark lines in nails. Other causes can include cancer, too much iron, and other health conditions.See full list on healthline.comThe outlook for most benign melanonychia is good and often does not require treatment. However, it usually does not go away by itself.Malignant melanonychia requires the removal of the tumor, which may also include amputation of the finger or toe. See full list on healthline.comDec 13, 2025 · A black line on your nail can range from benign (harmless) color variations to more serious conditions like melanoma. While sometimes harmless, any significant or sudden change should prompt a closer examination to rule out underlying medical issues. Noticing Dark Lines or Streaks in Your Nails? Black streaks in nails can be harmless or a sign of something more serious. While some causes, like trauma or fungal infections, are minor and treatable, others—such as melanoma—require urgent medical attention. · Black lines on your nails can be alarming, but they’re not always a sign of something serious. There are several possible causes, ranging from harmless pigmentation to underlying health conditions. · A black line on your nail can range from benign (harmless) color variations to more serious conditions like melanoma. While sometimes harmless, any significant or sudden change should prompt a closer examination to rule out underlying medical issues. Noticing Dark Lines or Streaks in Your Nails? Black streaks in nails can be harmless or a sign of something more serious. While some causes, like trauma or fungal infections, are minor and treatable, others—such as melanoma—require urgent medical attention. · Black lines on your nails can be alarming, but they’re not always a sign of something serious. There are several possible causes, ranging from harmless pigmentation to underlying health conditions. Noticing Dark Lines or Streaks in Your Nails? Black streaks in nails can be harmless or a sign of something more serious. While some causes, like trauma or fungal infections, are minor and treatable, others—such as melanoma—require urgent medical attention. · Black lines on your nails can be alarming, but they’re not always a sign of something serious. There are several possible causes, ranging from harmless pigmentation to underlying health conditions. · Melanonychia is a brown or black discoloration on your nail. These can be harmless. But they may be a sign of an underlying condition or skin cancer. That’s why it’s important to get an accurate diagnosis. If you notice changes to your nails, contact a healthcare provider. Contents What Is Melanonychia? · Melanonychia is dark nail discoloration caused by pigment buildup. Learn its causes, risks, and treatment options.
