Black Streaks Under the Nails: Causes, Symptoms & Best Treatment 2019

Black Streaks under the nails (fingernails or the toenails) can be very dangerous. Make 100% sure that you don’t have something more dangerous!


Black Streaks under the nails (fingernails or the toenails) can be very dangerous. Follow our diagnosis guide to see if you should be worried!




  • The most common cause of black under the toenails is dry blood.
  • Most People Should Not Be Worried!
  • A thick black dark streak could be a subungual melanoma- a type of skin cancer.
  • Don’t be too worried though, the odds are low that you actually have this tough, but better safe than sorry!
  • Watch the video above to get a better idea if this is what you have.
  • But always make sure to get checked out.


Black Streaks Under the Nails: Causes, Symptoms & Best Treatment 2019
A black streak under the toenails is almost always dry blood. But make sure to get checked out by a podiatrist if worried!

Dangerous Causes Black Streaks Under the Fingernails or Toenails:

  • Subungual melanoma is the most dangerous cause. It is a very rare form of skin cancer; it is usually seen between ages forty to seventy. It is not due to sun exposure or trauma. It just appears one day without any incident. If your dark spot appears after an injury then you are most likely on the safe side.


Safe Causes of Black Streaks in the Fingernails and Toenails:

  • The odds of the streak in your fingernail are actually pretty low because a lot of people, especially African Americans normally have light thin streaks of dark pigment that that form a vertical line down their nail which is completely normal. It is very easy to predict whether the streak is dangerous or safe.
  • Normal vertical streaks of pigment that are not melanoma. This is especially common in non-white individuals. These are usually thin lines in a very normal looking nail; check the guide below to see if you are on the safe side or if you should go get it checked out.
  • Trauma and loss of fingernail leading to a streak of blood. But this should eventually grow out at 1mm per month. If the blood is not advancing then you should get it checked out just to be safe!



Probably safe (but should still visit the podiatrist) if:

  • The streak is less than 3 millimeters in width.
  • The streak is uniform in length and of continuous color as it progresses down the nail.
  • The streak or pigment is only present in the nail and not in the skin.
  • The nail is not deformed, bloody or cracked in that area.
  • The nail looks normal compared to the other nails.



Visit a podiatrist for a biopsy immediately if:

  • The black streak is over 3 millimeters in width.
  • The streak is widest at the start of the nail origin.
  • The streak is not uniform or appears disrupted.
  • The streak changes color the further you get.
  • The streak continues from under the nail into the skin, termed “Hutchinson’s sign”.
  • The nail becomes deformed, bloody or starts to crack in the area of the streak.
  • The nail looks very unusual compared to the other nails.
  • The streak is more common in the thumb and the big toe.
  • The streak may even be white; in this case be aware of a nodule or irregularity that is forming under the nail plate.
  • If you have ever considered that there may be a wart underneath your nail that is just not healing.


Subungual Melanoma:

  • The outlook is usually very good if the cancer is confined to just the toe.
  • Most people that suffer from this disease have avoided seeking treatment for many, many years. It has usually spread far throughout the body.
  • If you are cautious and follow up on the streaking and ulcerating in a reasonable amount of time, you will most likely be safe.
  • The cure consists of excising the lesion or amputation the tip of your fingernail.
  • See your podiatrist as soon as possible!



Other Causes Of Black Spots Under The Toenail:

Other causes include:

  • Blood under the toenail.
  • Pseudomonas nail infections

Toenail Fungus Can Cause Black Streaks:

If the above does not sound like your situation, consider toenail fungus as well.

  • Toenail fungus is associated with 80% of all toenail problems.
  • It usually manifests as thick yellow toenails, but there can be brown and black marks as well.


Toenail Fungus Is Associated With 80% Of All Toenail Problems:



Symptoms of Toenail Fungus:

  • Thick yellow toenails.
  • Crumbling debris underneath the toenails.
  • Incurvated or possibly ingrown toenails.
  • Discoloration or streaking.

Click on this link to our comprehensive nail fungus home treatment guide. Always be sure to see a podiatrist if you are ever unsure!




Good Luck with the Black Streaks Under the Nails!