What is causing my black toenail?
If I had a pound every time I was asked that question… I’d be a rich lady!
I hear this a lot, particularly from runners here in Worcester who ramp up their training for their next marathon.
There can be a few different reasons why your toenail has gone black. The most common relates to trauma but there are a few sinister (and not so sinister) reasons why your toenail becomes black.
Let me help you work out which black toenail you have – and give a few pointers on what to do next.
This information is general advice for you. For specific advice about your own black toenail, you’ll need to see a podiatrist. This information does not replace any information you may have received one to one in the clinic.
Here are the top 6 reasons why your toenail is black:
- Blood under the nail
- Fungal toenail infection
- Bacterial infection
- Melanoma
- Staining from nail polish
- Sock fluff….yes this is a common one
Let’s take a look in more detail:
1. Is a black toenail a bruise?
It’s a bleed under your skin. Well, a bleed under your nail is called a subungual haematoma.
Just like a bruise on the skin, subungual haematomas can come in different levels of severity. You can get big bleeds under your nail which are incredibly painful as the toe is very sensitive (usually happen after a trauma like something dropping on your toe or repeated trauma from your nail bashing against the shoe when coming down a mountain).
There are also mild subungual haematomas where there’s only a small bleed and sometimes no pain at all.
To get a bleed under the nail, there needs to be trauma or damage to the area. Long-distance runners, fast bowlers and dancers are all familiar with black toenails from bleeding and trauma. These activities all bring the tops of the toes into contact with shoes and the ground and damage and bleeding can occur.
Have you knocked a toe against the door or coffee table and been heard swearing black and blue, you look down and see your toe has started to go the same colours?….. Yep, me too.
2. Toenail fungus could be the cause of your black toenail
Fungal toenails? Athletes’ feet that live on our skin normally can infect and thrive within our toenails, causing them to go black.
There are three culprits that can cause your black toenails:
- Trichophyton rubrum
- Epidermophyton floccus-um
- Trichophyton mentagrophytes
Great names for things that are not great when they’re growing on your toenails.
If any of those 3 types of fungus have their ideal growing conditions (warm, dark, moist, and plenty of food) they can take over.
So you might originally have a black toenail from a bleed under the nail, but if you’re not careful, this can turn into a fungal toenail pretty easily.
Here are some tell-tale signs that you might experience with a toenail fungus infection:
- Yellowish, brownish tinge to the black discolouration
- Crumbling or friable edges
- Thickening or hardening of your toenail
3. Bacterial infections of the toe and nail
Usually, when we think of bacterial infections of the skin and nail we think of either redness and swelling or severe pus, redness and an urgent need to get to hospital for antibiotics.
But there’s a sneaky type of bacteria that is found commonly in the garden in soil called pseudomonas aeruginosa, which can cause a black toenail.
Pseudomonas can be a tricky one as it’s resistant to many of the most common types of antibiotics prescribed for skin conditions which means it can take a while to treat correctly.
It leaves dark patches on and under the nail, and the pus (that oozy discharge that’s so gross and yet so satisfying to clear) has more of a green colour than the usual yellow.
If I had even the tiniest suspicion my toe and nail had a pseudomonas aeruginosa infection, I would be rushing to my podiatrist as fast as my legs would take me.
4. Melanoma (that awful skin cancer)
They’re dangerous and can be fatal and we all have someone within our circle of friends and family who’s suffered or suffering from skin cancer.
In the same way, you can get melanoma on your skin, you can get one within your nail. More accurately, within your nail matrix (or nail root). Not many people remember that when Bob Marley died, it all started sadly from a melanoma in his big toe. It could have been avoided but sadly it was ignored as a trauma but was actually a rare Acral lentiginous melanoma (ALM).
While the presence of melanoma in the nail is much less common than in the rest of the body (your toenails don’t usually see as much sun as your face), they still happen at too frequent a rate. When you combine the fact that you probably don’t look at your toenails anywhere near as you check your face, chest and shoulders, they can be missed for some time.
A black toenail from a melanoma tends to have a black line running through the nail, from the base to the tip rather than taking up the whole toenail. They are rarely painful. This means they become easy to miss in the first place and are ignored as it’s covered with your shoes and socks. They are more common in people of darker skin colour.
But please, if you have a black toenail which has a line running through it, go see your GP and have it checked out as soon as possible. It might be nothing, or nothing sinister, or that check-up could save your life.
5. Could your black toenail be from your nail polish?
Your toenails are porous, which means they can absorb liquids and “breathe” to allow gases through. When you cover them with nail polish you block these pores which can increase the likelihood of a toenail fungus developing.
Your polish can also stain and get through into your nail pores which leaves a discolouration, which can be the reason for your black toenails.
It’s for this reason that we recommend allowing your nails to be “nude” for periods of time breaking up your regular nail polish use. We also advise removing nail polish with an excellent nail polish remover and semi-regularly seeing your podiatrist for treatment (medical pedicure).
Part of this treatment will involve mechanical burring (an electric drill-like file) that removes the outer layer of the nail and polish staining.
6. Sock fluff
As odd as it sounds, sock fluff can get compacted and stuck down the sides of the nail sulci or any part of the nail that separates.
It is not usually painful but if it persists, moisture can gather under the nail and fungal spores can develop there, thus starting fungal infections.
To get rid of the fluff trim your nails and use a file to thin the nail where needed using a soft toothbrush brush away the skin and fluff using soapy water and some baby oil (this helps to loosen it)
Sock fluff under the nail can look a lot similar to other conditions mentioned above.