Help! Why Do I Have Black Toenails?

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A black toenail – whether the whole nail or just a small part of it – can be caused by a number of things, including toenail fungus.

Athletes, especially runners, are also known to suffer from black toenails, while trauma to the nail can also blacken them.

We’ll run through the possible causes for black toenails and what you need to do to treat them.

Remember – it’s always best to consult your doctor who will be able to give you advice and treatment tailored to your specific needs.

Causes of black toenails

  • Fungal Nail Infection: toenail fungus can discolour the nail.
  • Subungual hematoma: a trauma to the nail will lead blood to gather underneath it, darkening its appearance.
  • Repetitive trauma: otherwise known as ‘runner’s toe’, this is when the nail repeatedly hits the end of the shoe, leading the nail bed to bruise and darken. This can also affect people who wear ill-fitting shoes.
  • Melanoma: although rare, a dark spot under the nail can indicate a melanoma. Your doctor will be able to perform a biopsy to check for you.

Symptoms of black toenails

  • A dark spot under the nail that may affect part or the whole of the nail
  • Pain and pressure
  • A thickened nail
  • A foul smell from the nail
  • The nail may begin to come loose from the nail bed and even fall off in advanced cases

How to cure black toenails

Treatment for black toenails will differ depending on what’s caused them.

A trip to your doctor or podiatrist will able to diagnose the problem and advise on the best course of treatment. While many people choose to treat toenail fungus and ‘runner’s toe’ at home, subungual hematoma and melanoma will need to be diagnosed and treated by your doctor.

Fungal Nail Infection

You’ll be able to tell if you have black toenails as a result of a fungal nail infection if you’re also suffering from the following:

  • Nail thickening
  • Possible separation from the nail bed
  • A foul odour
  • A build-up of debris under the nail
  • Some pain if you’re putting pressure on the nail

Toenail fungus is very common and can be picked up easily, particularly if you’re walking barefoot in public areas – nail salons and swimming pools are notorious for spreading toenail fungus.

It can be difficult to effectively treat fungal nail infections and there is not yet a fail safe guaranteed cure option. However, many people find relief and cure from the following treatments:

Our main page provides an in-depth run-down on the best treatments on the market right now.

To avoid toenail fungus, remember to do the following:

  • Keep nails clean with a regular anti fungal wash and always dry them thoroughly
  • Only visit nail salons where you know that hygiene is a priority
  • Don’t go barefoot in public areas
  • Keep your toenails trimmed short
  • Always wear shoes that fit correctly

Runner’s Toe

black toenails
The feet of a marathon runner, by reflexblue (Creative Commons)

As you can guess, most people suffering from ‘runner’s toe’, or repetitive trauma, are generally runners and athletes who experience a great deal of repetitive hitting between the end of their nails and the end of the shoes they’re wearing.

However, anyone who wears ill-fitting shoes can also be at risk of this. It’s particularly common in the second and third toes of the foot.

You may also notice a slight thickening of the nail with runner’s toe.

As far as treatment goes, your doctor will be able to advise you on what is best for your toe.

It’s particularly important to visit the doctor if over 25% of the nail is black as this could indicate a bigger trauma, or a subungual hematoma.

In most minor cases, the nail will either grow out within a few months or, in some cases, fall off completely and regrow. If that does happen, be aware that the nail is likely to grow back differently to the original nail.

Subungual hematoma

Subungual hematoma is much less common than toenail fungus and runner’s toe, but it is known for being very painful and requiring the intervention of a doctor.

It’s likely that you’ll remember how the hematoma started as it will have come about due to trauma – likely a heavy object was dropped on it, or the nail was stepped on.

The trauma will see a pool of blood collect under the nail, making it appear black.

It’s also likely that you’ll also suffer from some pain and throbbing, particularly if a large part of the nail is affected.

When there is a great deal of pressure on the toenail, your doctor may decide to drain the blood. They can do this by either a large-gauge needle or even by a cautery: a device that burns a hole into the nail to allow drainage.

In other cases, they may decide to remove the entire nail under local anaesthetic to check whether there is a significant laceration or even any exposed bone.

They will then examine, clean and suture the laceration, as well as deal with any fractures or infections caused by the trauma.

It’s very important to have your subungual hematoma diagnosed and treated – complications can otherwise arise leading to bone infections and even amputations.


black toenails
Melanoma can present itself as dark stripes on the toenail (via NHS)

Melanoma – a malignant tumor usually associated with skin cancer – is very rare under the toenail but not unheard of. Bob Marley was found to be suffering from this in 1977, for instance.

Early diagnosis and treatment of melanoma is important for a good outcome, so be sure to see a doctor immediately if you have a dark spot or stripes under a toenail – particularly if you can’t remember any significant trauma that might have caused it.

Your doctor will be able to test the toenail for melanoma, possibly by using a biopsy, and will question you on your family’s medical history to best judge the outcome.

Treatment for melanoma will depend on the size and severity of your particular case. Surgery is generally enough to tackle early melanoma while chemotherapy and radiotherapy may be needed in more advanced cases, according to Cancer Research.