Why do I have a black toenail and how can I treat it?

Black toenails are common among triathletes, but what causes them and how can they be treated and prevented? Nick Beer provides the answers…

Published: April 13, 2023 at 1:35 pm

There are many theories that surround the evolution of our nails. Some suggest they may have begun as claws; used to pick up food and tightly hold objects. Other theories mention they may have played a crucial role in climbing and tearing up food.

The human species has had to adapt to the ever-changing landscape, and therefore the role of our nails has significantly transformed. We may still, at times, apply some ancestorial traits, but our nails primarily serve to protect the vulnerable areas of our fingertips and toes.

Why is my toenail black?

Our toenails are made of a protein called keratin, the same protein that makes up our hair and skin. They can, like many other parts of our body, be prone to infection.

Fungal infections have been known to cause black toenails. Typically, white, or yellow in colour, they can materialise to a black fungus and even spread.

In more serious cases, a black toenail could represent an underlying health condition. If unsure, consult a doctor for further information.

However, in most cases, a black toenail is typically caused by physical trauma – such as being stubbed, stamped, crushed, or exposed to prolonged repetitive knocks. These traumatic actions cause the blood vessels underneath the nail to break, which results in discolouration of the skin – often known as a bruise.

A common diagnosis of a black toenail is 'Runner's Toe'. It occurs when your toe repeatedly rubs and hits into your shoe, causing the nail to become stressed. Bruising results and blood pools in the nail, forming a black toenail.

Not exclusive to runners, it can often affect rock climbers, football, rugby, tennis, and squash players, or any sport where ongoing foot movements could place the nail in a vulnerable position to being bashed or have something dropped upon it.

How do I stop my toenail from turning black?

There are several ways to prevent a black toenail:

  1. Wear the right shoes – ‘Choose the right equipment’ has always been a phrase associated with positive outcomes. Most activities will require decent and durable footwear. If you sell yourself short, do not take your time to try out a variety of shoes for your activity, and do not invest properly, you could run the risk of securing detrimental returns.
  2. To avoid a black toenail, choose a size where you have enough room, so your toes aren’t pressed tightly against the fabric. If you go too large, your foot can slide around making it easier to cause injury. For future purchases, aim for one thumb width away between the tip of your toe to the end of the shoe.
  3. Trim your toenails – Clipping them short will ensure that it will be your toe and not your nail, that hits the inside of your shoe. The shorter they are, the less likely they are to strike your shoe. Leaving you with a pain free toe and an enjoyable experience.
  4. Lace your shoes properly – You may get away with poorly tied laces for a short walk, but anything longer or more arduous, lacing them up correctly is an important way to avoid injury. Tying your shoes up before your exercise will:
    · Allow for proper blood flow.
    · Provide flexibility.
    · Prevent rubbing.
    · Avoid putting pressure on delicate areas.
    · Keep your heels locked in place to help prevent a potential ankle sprain.
  5. Wear moisture-absorbent socks – Damp toes can be hazardous. They could slip and cause your feet to slide, enabling your toes to move around freely. You will instinctively try and stop the movement by gripping your toes on the sole of the shoe. This will unknowingly move your toenail either up or down repetitive times, that will inevitably lead to bruising. A pair of quality socks that will transfer sweat to the fabric and are quick drying, so the sweat doesn’t soak through the fabric, will help to keep your feet firmly in place.
  6. Use toe protectors – If you are susceptible to black toenails, silicone toe caps could help to guard against friction and provide cushion from repetitive movements. They stretch to fit any toe and fully cover all sides. They are great for cushioning and stopping the friction that can cause blisters. Some can also be cut down to size, allowing a perfect fit customised to your foot.

How do you treat black toenails at home?

Before you try more invasive modalities, you can treat your black toenails at home. A popular method is to soak your toenail in cold water for 20 minutes.

Dry your feet and apply some anti-fungal cream – you may have had this already prescribed from the doctor or you can pick it up from your local pharmacy.

Once finished, cover your toenail with a fresh bandage. If you find your toenail is beginning to detach, carefully file down the nail. This will stop further tearing.

You may decide to try some homeopathic remedies. For example, soak your foot in apple cider vinegar, which contains acetic acid that is proven to have antifungal properties.

Or you could apply tee tree oil on to the infected area with a cotton swap. The herbal medicine has antiseptic and antifungal properties that may help clear the black fungus.

If your toenail is causing mild pain, NSAIDS, like ibuprofen, are typically taken to reduce inflammation and manage pain (always read the dosage instructions on the packet before ingesting).

Will a black toenail go away?

If you are not experiencing any pain or complications, no specific treatment is needed. The black toenail should go away on its own. However, sometimes your nail may fall off. If this happens, clean it with antiseptic cream and cover your toe to allow it to heal.

It is important to note: if your nail begins to show signs of infection, abnormalities – such as redness, swelling, pus discharge, or the nail won’t grow naturally – it may be advisable to speak to a doctor for further guidance.

Top image credit: Getty Images