The word “melanonychia” comes from Greek:
“Melas” = black or brown
“Onyx” = nail
Melanonychia means a dark brown or black line (or band) that appears on the nail. It happens when pigment (melanin) collects in the nail plate. The line can be thin or wide, can affect one nail or several nails, and it may appear on both fingernails and toenails.
Melanonychia occurs because of changes in melanocytes (the cells that make melanin, the pigment that gives color) become active. There are two main ways this happens:
Melanocytic activation – the number of melanocytes stays the same, but they produce more melanin.
Melanocytic hyperplasia – the number of melanocytes increases. This can be benign (harmless) or sometimes malignant (linked to nail melanoma).
Causes of melanocytic activation:
Racial differences – More common in people with darker skin
Pregnancy – Hormonal changes may cause streaks in multiple nails.
Fungal infections – Some fungi make melanin that gets into the nail.
Bacterial infections – Especially in people with weak immunity
Viral infections – People with HIV may develop nail streaks.
Skin conditions – Psoriasis, lichen planus, amyloidosis.
Trauma – Nail biting, chewing, friction, or repeated injury.
Tumors – Both benign and malignant.
Systemic diseases – Addison’s disease, Cushing’s syndrome (often multiple nails affected).
Drugs – Certain medications can cause transverse (horizontal) streaks.
Medical treatments – Chemotherapy, radiation, or X-rays may trigger changes.
Note: Many causes are harmless, but melanonychia can also be a sign of nail melanoma, especially if the band is irregular, widening, or only in one nail.
There are three main types:
Longitudinal melanonychia (melanonychia striata):
The most common type.
Appears as a long, narrow band running from the cuticle to the tip of the nail.
Diffuse or total melanonychia:
The entire nail plate looks dark or discolored.
Transverse melanonychia:
A horizontal band of color that runs across the width of the nail.
Not always. Many cases are harmless, especially if seen in multiple nails or in people with darker skin. But if the line appears suddenly, changes shape, widens, or is only on one nail — it needs to be checked urgently because it can sometimes be a sign of melanoma.
Contact a dermatologist if you notice any of these:
A new dark line or streak on a nail (especially if it affects only one nail).
The band becoming wider, darker, or changing shape over time.
Irregular or blurred borders of the streak.
Nail changes such as cracking, bleeding, or pain.
Dark pigment spreading to the surrounding skin (known as Hutchinson’s sign).
A band that is wider than 1/8 inch (3 mm).
A dermatologist will:
The doctor first asks about your health, medications, and any history of trauma or illness.
They then check how many nails are affected, and look at the pattern, color, and shape of the dark streaks.
The doctor may use a tool called a dermatoscope to look at your nail closely.
This helps them tell melanonychia apart from other conditions:
For example, a splinter hemorrhage (tiny blood clot under the nail) looks like a reddish-brown streak, but it’s different from melanonychia.
If the doctor suspects something serious like nail melanoma, they may do a biopsy.
This means removing a small part of the nail or nail bed and checking the cells under a microscope.
A biopsy is the gold standard (most accurate test) for confirming whether the streak is benign (harmless) or malignant (cancerous).
If the streak is not dangerous, treatment may not be needed.
Medication-related: If a medication caused the discoloration, the streak often fades within 6–8 weeks after stopping that medicine.
Infections: Treated with antifungal or antibacterial medicines.
If the melanonychia is due to nail unit melanoma (NUM), treatment is more serious.
A doctor may recommend surgery, which could involve:
Removing the entire nail unit.
In severe cases, amputating the tip of the finger or toe to stop the spread of cancer.
Not always. But protecting nails from repeated trauma (like tight shoes), avoiding unnecessary medications, and regular nail checks help.
Fact: Most dark lines are harmless and caused by things like injury, medicines, or natural skin color. Only a small percentage are linked to melanoma.
Fact: Nail melanoma often doesn’t cause pain in the beginning. A painless but changing line can still be dangerous.
Fact: It can occur at any age — children, young adults, and older people. However, melanoma is more common in adults.
Fact: Melanoma usually affects one nail. Lines on multiple nails are more often harmless (racial pigmentation, medication, or systemic conditions).
Fact: Only a dermatologist can confirm the cause — sometimes with a biopsy. Self-diagnosis can be misleading and risky.
Fact: Since the pigment is inside the nail, trimming won’t make it disappear.
Fact: No oil, cream, or home trick can remove the pigment. The cause needs to be identified by a doctor.
Fact: Melanonychia is pigment inside the nail plate, not dirt that can be cleaned off.
Melanonychia is not just “one cause” — it can come from skin tone, infections, trauma, systemic diseases, or even medications. Most cases are harmless, but any sudden, single-nail, or changing dark line must be checked by a dermatologist to rule out melanoma.
Disclaimer: This article is only for general patient information and is not intended for self medication. There is no legal liability of IADVL arising out of any adverse consequence to the patient. Subsequent to its use for self treatment of the disease images adjust for the depiction of the condition and is not to be used for any other purpose.
Explore articles in this section to gain a deeper understanding of various skin diseases and conditions. Each article provides detailed information on symptoms, causes, and treatment options, helping you to manage and address these dermatological issues effectively.
Psoriasis is a skin condition where new skin forms at a faster rate, showing up as red rashes with whitish scales, commonly over elbows, knees, and other body parts.
Dandruff is a common scalp condition in which small pieces of dry skin flake off from the scalp and is usually associated with itching. The exact cause of Dandruff and Seborrhoeic Dermatitis is unknown.
Dermatophyte infection is a superficial fungal infection of skin, hair and nails. It is also known as ringworm. In Hindi it is termed as Daad and in Marathi it is termed as Gachkaran.
