What is That Black Spot on Your Toenail?
What Is That Black Spot on Your Toenail?
It can be relatively alarming to look down at your toenail and see a black spot that seemingly occurred out of the blue. You're wondering "What is this black spot and how in the world did it happen?" Black spots on toenails are incredibly common, and most of the time, they're nothing to panic about.
As a podiatrist of 30 years, it is really something that I see multiple times a day in the clinic. The vast majority are completely harmless—just blood trapped under the nail from minor trauma usually something that can't be recalled.
But I also want you to know when it actually matters and what you should do about it.
The Most Common Cause: Subungual Hematoma
A black or dark bruise on your toenail is usually a subungual hematoma—blood that's pooled under the nail. Think of it like a bruise on your skin, except it's under the nail bed.
Your toes are literally the first part of your body that swings out in front of you as you walk. They're vulnerable. We are rudely reminded of this every time we go to the bathroom at night in the dark and stub our toes.
A stubbed toe, a kick during soccer, a repetitive banging of toes in the toe box of a hiking boot or running sneaker —any of these can cause small blood vessels (capillaries) under the nail to break. That blood accumulates in the space between the nail bed and the nail itself, creating that dark spot you see.
The important thing to know: Most of these bruises happen without you even noticing. You might stub your toe and not feel it which most of my patients don't remember any toe trauma .
Why Athletes Get Bruised Toenails More Often
If you're a runner, soccer player, football player, runner, or hiker, you've probably dealt with this. Here's why:
Repetitive friction. Your toe is constantly rubbing inside your shoe. Over time, that friction—what we call "shear force"—breaks those tiny blood vessels. For runners especially, the constant pounding and the toe box rubbing can cause microtrauma over weeks or months.
Sometimes this is so painful it forms a blood blister ( see below), which usually sends people to the ER or urgent care and results in losing the nail. Sometimes, it can be drained instead. Something like this can happen with running or hiking. However, if something traumatic happened such as stubbing the toe hard or something falling on the toe, there could be a fracture so it is important to see a doctor.
<== This is very painful.
Sometimes it's just a slow accumulation of tiny bleeds that shows up as a dark spot. Either way, if this is happening to you regularly, there's a solution—more on that below.
How Long Does It Take for a Bruised Toenail to Go Away?
Here's what I tell my patients: give it at least 6 months.
Toenails grow slowly—about 0.1 millimeter per day. That means a full toenail takes roughly 6 months to completely regrow. As the healthy nail grows up from the nail bed, it will gradually push the bruised portion out. Sometimes it grows through the nail and flakes off. About half the time the entire nail may fall off on it's own. Sometimes as it grows out, it is partially attached and irritating so a podiatrist can trim the loose part off easily without hurting you.
<<== dried blood growing out of the nail.
If the dark spot hasn't grown out in 6–8 months, it might be something else. That's when you should start thinking about whether there's another cause.
Other Causes of Dark Spots on Toenails
Fungal Infection
Sometimes what looks like a bruise is actually a fungal infection. The difference? Fungal nails are usually thick, brittle, and yellowish-brown—not just a dark spot. They're also stubborn and don't go away on their own. Check out my full guide on fungal toenail treatment if you think this might apply to you.
Melanonychia
This is a brown or dark line that runs lengthwise down your toenail—and here's the important part: it's completely normal and harmless.
About 70% of people with darker skin tones have melanonychia, compared to only about 1% of people with lighter skin. This is because darker skin naturally produces more melanin, and these dark lines on nails are simply a normal expression of that. If you have darker skin and see a dark line on your nail, this is most likely what it is.
Typically these lines are well defined and have been present and unchanged for a long time. However, if they suddenly appear after age 30, then see a dermatologist as soon as possible.
When to Actually Worry: Red Flags to Watch For
While dark spots on toenails are almost always harmless, there are a few rare conditions that can look exactly like a bruise. Here's what to watch for.
🚨 Red Flag #1: Subungual Melanoma
Melanoma is a skin cancer . Overall, the lifetime risk of getting melanoma is about 3% (1 in 33) for White people, 0.1% (1 in 1,000) for Black people, and 0.5% (1 in 200) for Hispanic people per American Cancer Society. Melanoma of the nail unit is incredibly rare. Melanoma of the nail unit occurs accounts for around 0.7–3.5% of malignant melanomas in white-skinned populations and up to 75% of dark-skinned and Asian populations according to DermNet So, ironically , overall melanoma risk is much more rare in darker skinned individuals, BUT nail unit melanoma is more common in people with dark skin.
Although rare, it must be kept in mind and dark spots require monitoring and investigation at times. Dermatologists use the ABCDEF rule to check for suspicious nail lesions:
- A — Age: Usually appears in people 50 and older. It's more common in people with darker skin tones (African Americans, Asians, Native Americans).
- B — Band: The dark band is brown or black, wider than 3 millimeters, with blurry edges.
- C — Change: Is the band growing or changing shape? Is there a wound? Is it not resolving after treatment?
- D — Digit: Melanoma usually appears on the thumb of the dominant hand or the big toe.
- E — Extent: Is the dark color spreading to the skin around the nail? (This is called "Hutchinson's sign" and is a red flag (see below)).
- F — Family history: Do you have a personal or family history of melanoma or unusual moles?
If you see any of these signs, see your dermatologist. They'll use a dermatoscope for a closer look and may do a biopsy to be certain.
🚨 Red Flag #2: Splinter Hemorrhages & Endocarditis
Endocarditis—a heart infection of valves or heart lining —can sometimes cause tiny splinter-like bruises under the nails.
This is very rare.
It occurs in susceptible individuals, when bacteria enters the body from perhaps dental work or skin infection and then travels to the heart. Again , this is uncommon but risk factors for endocarditis include poor dental health and gum disease, heart conditions, having an artificial heart valve surgery, diabetes, IV drug use and you're developing bruises under your nails plus feeling feverish, weak, or short of breath. That combination warrants an ER visit right away.
What to Do If You Have a Bruised Toenail
- Take a photo. Document it now so you can track whether it moves with nail growth over time.
- Watch it. Over 6 months, observe whether the dark spot moves up with new nail growth. If it does, it's trauma. If it stays in one place, it might be something else.
- If you see any ABCDEF warning signs, see your dermatologist. Get it checked.
- If you play sports or hike, prevent it. Gel toe caps are a simple, effective fix. The gel does a fantastic job absorbing pressure and friction—I recommend them to my athletic patients with repeated nail trauma.
- If the nail falls off, protect it. Use tea tree oil or a topical antifungal medication while the new nail grows back to prevent fungal infection from taking hold.
Prevention: How to Stop Bruised Toenails
Gel Toe Caps
These small, cushioned gel caps go over your toes inside your shoe. The gel reduces the shear force that causes microtrauma. I've recommended these to athletes especially hikers and runners, and they work. Shop gel toe caps here.
Below all gel cap : Gel lined fabric cap below:
Proper Shoe Fit
Make sure your athletic shoes have enough room in the toe box. Your toes shouldn't be crammed. Shoes designed for runners should have more forgiving mesh stretchy toe boxes than regular footwear.
The Bottom Line
A black spot on your toenail is most of the time nothing to worry about. It's usually just blood trapped under the nail from trauma, and it will grow out over about 6 months.
But you need to know what to watch for. If you see two or more ABCDEF warning signs, see a dermatologist. If you're getting bruised nails repeatedly from sports or hiking, use gel toe caps to prevent it. And if you've had recent surgery or dental work and you're developing bruises under your nails plus feeling feverish or weak, see your doctor right away.
Have questions? Drop them in the comments on my YouTube video "Bruised Toenail: When to Worry", or leave a comment here.
Thanks for reading and here's to your best foot forward!
Melissa Gaffney, DPM
References:
Eleven Myths on Nail Melanoma 11 Nov 2021 Dermatology https://www.emjreviews.com/en-us/amj/dermatology/article/eleven-myths-on-nail-melanoma-j030121/
Melanoma of the nail unit : https://dermnetnz.org/topics/melanoma-of-the-nail-unit Author(s): Dr Nicole A. Seebacher, Department of Oncology, University of Oxford, UK. Copy edited by Gus Mitchell. February 2022
Key Statistics for Melanoma Skin Cancer: https://www.cancer.org/cancer/types/melanoma-skin-cancer/about/key-statistics.html https://my.clevelandclinic.org/health/diseases/16957-endocarditis
Frequently Asked Questions
What causes a black spot on a toenail?
The most common cause is a subungual hematoma — blood trapped under the nail from trauma. This can happen from stubbing your toe, repetitive friction in athletic shoes, or even minor impacts you don't remember. Most of the time, it's completely harmless.
How long does it take for a bruised toenail to go away?
Plan on at least 6 months. Toenails grow about 0.1mm per day, so the bruised portion slowly grows out as the healthy nail replaces it. If the dark spot hasn't moved after 6–8 months, it's worth having it evaluated.
Will my toenail fall off after a bruise?
About half the time, yes — the nail may detach on its own as it grows out. This sounds alarming but is usually painless. A podiatrist can trim any loose portion if it becomes irritating.
How do I know if a dark toenail is melanoma?
Melanoma of the nail is rare, but use the ABCDEF rule to check: look for a dark band wider than 3mm with blurry edges, spreading to surrounding skin (Hutchinson's sign), appearing after age 50, or changing over time. If you see two or more of these signs, see a dermatologist promptly.
Is a dark line running down my toenail dangerous?
Usually not. A lengthwise dark line is often melanonychia — a normal expression of melanin pigment, especially common in people with darker skin tones. However, if it appears suddenly after age 30, see a dermatologist to rule out other causes.
How is a bruised toenail different from a fungal infection?
Fungal nails are typically thick, brittle, and yellowish-brown — not just a dark spot. A bruise will gradually grow out with the nail; a fungal infection won't resolve on its own and usually requires treatment.
How can athletes prevent bruised toenails?
Gel toe caps are the most effective solution — they absorb the shear force and friction that causes microtrauma inside the shoe. Proper shoe fit with adequate toe box room is also essential, especially for runners and hikers.
When should I go to the ER for a bruised toenail?
If you have a painful blood blister under the nail after significant trauma, see a doctor — there may be a fracture, and the blister may need draining. Also seek emergency care if you have dark spots under multiple nails plus fever, weakness, or shortness of breath, as this can rarely signal a heart infection (endocarditis).
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