Could Your Black Toenail Be More Than a Bruise? Learn the Warning Signs

 Black Toenail? Here’s What It Means and What You Should Do

A dark toenail isn’t always harmless—know when it’s time to seek medical care.

A black toenail can be alarming the first time you notice it. While it is often caused by a minor injury, discoloration beneath the nail can sometimes signal an infection or, in rare cases, a more serious medical condition. Understanding the possible causes and knowing which warning signs require medical attention can help you protect your foot health and avoid unnecessary complications.

The Most Common Cause: A Bruised Toenail
The leading cause of a black toenail is a subungual hematoma, which occurs when blood collects beneath the nail after an injury. This can happen if you accidentally drop a heavy object on your foot, stub your toe, or repeatedly place pressure on the nail while running, hiking, or wearing tight-fitting shoes.

As blood becomes trapped beneath the nail, the toenail gradually turns dark purple, brown, or black. Over time, the discoloration slowly moves toward the tip of the nail as it grows out.

Typical symptoms include:

Pain or throbbing shortly after the injury
Tenderness when pressure is applied
Dark discoloration beneath the nail
Mild swelling around the toe
If the pain is severe because of pressure beneath the nail, a healthcare professional may be able to relieve it by draining the trapped blood.

Could It Be a Fungal Infection?
Not every black toenail is caused by trauma. A fungal infection may also darken the nail, although the discoloration often appears yellow, brown, or black over time.

Other signs of a fungal nail infection include:

Thickened toenail
Brittle or crumbly edges
White or yellow streaks
Distorted nail shape
Unpleasant odor
Unlike a bruise, fungal infections usually develop gradually and often require antifungal treatment.

When a Black Toenail May Be More Serious
Although uncommon, persistent dark pigmentation beneath a toenail that does not follow an injury should always be evaluated by a healthcare professional. In rare cases, it can be associated with subungual melanoma, a type of skin cancer that develops under the nail.

Warning signs include:

A dark streak or spot that gradually becomes larger
Pigment extending onto the surrounding skin
No history of trauma
Persistent discoloration that does not grow out with the nail
Changes in the nail without an obvious cause
These symptoms do not automatically mean cancer, but they should never be ignored.